Flats Retrofit Toolkit

Considering what's possible

Perhaps you have seen solar panels on the roof of a similar block, or flats are cold and you want more insulation in the walls. Before you do anything else, we recommend you work through the following first steps.

Look at the options and understand the range of different measures that could make your building lower-carbon and more energy-efficient.

To find out more about what is possible, have a look at our case studies in section 4 and read up on the range of different energy upgrade measures.

It can be good to have a specific idea about improving the building, such as fitting solar panels, but try to keep an open mind about what else is possible as there may be other ways of making a building lower-carbon and more energy-efficient. A review of options would look at the full range of retrofit options. 

Bear fabric first and whole building principles in mind. It’s often better to fit insulation before you make other types of upgrade. If possible, it can be better to plan upgrades on the basis of the whole building, rather than parts of the block or individual flats.

You will probably want to think about what upgrade measures will cost. It is possible to get started with cost estimation early in the project by using case studies of similar projects, published cost data and existing guidance, such as that from LETI.

Think about what your priorities are and what outcomes and benefits the upgrades would bring.

While looking into upgrade options, think about what might matter to other stakeholders in your building. Reducing energy costs? Reducing the carbon footprint of the building? Replacing or upgrading heating systems that are expensive or do not work well? Is there broad agreement on the priorities between the stakeholders, or do you think some people have different ideas or won’t be interested at all?

Consider any planned works.

Consider how possible upgrades relate to the type of building, and how upgrades might relate to any ongoing or planned works.

Understand how your building is owned and managed

Anyone considering retrofit in a block of flats must understand in detail how their building is owned and managed. Use the resources and information from the Government-funded Leasehold Advisory Service to ensure you understand the terminology and the roles of the different people who own, lease, manage, live in, or have other types of interest in the building, such as mortgage lenders.

Decision-makers are the people who have the authority or influence to decide to explore options for retrofit your block in more detail.

Decisions always need to be made based on what is permitted within the terms of lease - see section 3.3 for information on lease terms. Before works can proceed, consent may be needed from other parties, such as mortgage lenders, as well as planning permission.

Presenting the idea

The key message to take to decision-makers at this stage is: “I’d like us to investigate what can be done to make this block better and more sustainable. There are several upgrades we could consider that could reduce energy bills for residents, potentially increase property value for the leaseholders and the landlord, and reduce costs and hassle for the building managers.”

The more information you have before you go and speak to decision-makers, the better. We have shared tips on how to present an idea for retrofit in section 5.1. Before you start the conversation, write down your ideas on the following six points: 

• The changes you would like to see - identify some of the best-practice examples from our case studies in section 4 and information about different upgrade measures in section 5 that you think might work for your block. Include a range of ideas – not just one. 
• Why upgrades are right for this building - based on the building characteristics and any current or planned work. 
• The shared benefits -  see below for ideas on how to ‘sell’ the idea to landlords and managing agents. 
• Getting leaseholders and residents on board - explain how you think leaseholders and residents will come on board with the idea.
• Explain the next step - a review of options (see section 2.2) can be undertaken by an expert. Reassure decision makers that at this stage this is just about identifying possible upgrades from the information available.

Making the case: key messages for landlords and building managers

Making the case: key messages for leaseholders

Leaseholders can be divided into those who occupy their flat and those who sub-let their flats. The benefits of retrofit upgrade will be different for the two types of flat owners.

Potential benefits for resident leaseholders

• A home that may be cheaper to run, helping to cut energy bills, and that insulates you against price rises.
• A more comfortable flat that’s easier to keep warm in winter and cooler in summer.

Potential benefits for non-resident leaseholder

• Lower energy bills and better comfort levels, making the flats more attractive for new tenants.
• Existing tenants may be likely to stay for longer and are less likely to get into rent arrears if the energy bills are lower and the flats are more comfortable.

Potential benefits for all leaseholders

• Long-term lower service charges as the building is better maintained, and communal energy bills are lower.

• Contribution to cutting carbon emissions.

• Higher property value.

Who is this section for?

This section is for landlords, leaseholders with management responsibilities and building managers.

What does this section cover? 

A review of retrofit options across the building will estimate both the costs and the benefits of the retrofit improvements; it will be key to starting to think about financing and detailed design, as well as the potential to tie into any other works being considered. 

Once potential upgrades have been identified it will be necessary to consider them in relation to how the building is owned and managed, the consents needed for the works to proceed and how the costs will be allocated.

Supporting Resources: 

Information that may be useful to collect about the building to inform a retrofit plan is in section 6. 

An example of a simple review of options is available on the Repowering London website. 

See also our information sections about grants (section 3.1), planning rules (section 3.2) and leases (section 3.3).

Step-by-step overview of this section 

• Collecting information. 

• Considering management arrangements, the terms of leases and the requirements for other permission to carry out works (‘consents’). 

• Appointing an expert to carry out the review of options across the building. 

• Comparing options and next steps: thinking about financing and a business plan.

Collecting information

The information that it may be useful to collect about the building to inform a retrofit plan is in section 6. 

The more of this information that can be gathered, the easier, more cost-effective and more accurate a review of options is likely to be. 

It may be appropriate to collect information from leaseholders and residents. For example, is their home cold? Do they think their bill is higher than it should be? Leaseholders and/or residents may want to compare energy bills information. Before collecting and storing any data, make sure you comply with data protection rules.

Considering ownership and management arrangements, the terms of leases and other consents issues

Lease terms will directly affect thinking about potential upgrades: for example, lease terms will determine what consent is required for measures to be installed in different parts of the building, and whether costs of measures to the communal parts of the building can be recharged to leaseholders through the service charge (in private sector blocks usually subject to a Section 20 consultation). It is also important to consider what other consents might be required, for example from mortgage lenders. This is a point at which early legal advice should be sought and is likely to be something considered before proceeding with the review of options. 

More information on leases is provided in Section 2.3. To understand more about leases and leasehold law, see the government-funded LEASE Leasehold Advisory Service.

Appointing experts to review options for the building

Considerations

It is important to understand the current condition and performance of your block first, before assessing upgrade options. You will need to engage the relevant professionals and experts appropriate for your context, but often this might involve a building survey. A building survey can help provide the baseline to be benchmarked against when considering improvements and their impacts, and will also help identify any enabling works or maintenance necessary to deliver a quality retrofit.  

Different experts will use different tools and methodologies to analyse your building and consider costs and benefits of different possible upgrades at the level of the building and/or the individual flats.  

There are a growing number of companies that offer thermal imaging surveys, and many surveyors may also provide it too. A thermal imaging survey will measure moisture, leaks and heat loss that can point to areas of concern and therefore areas for improvement.  

Providers of specific retrofit measures may carry out detailed assessments of the potential for the measures of interest, such as how much energy would be generated by solar panels, or heat pumps. 

Retrofit Assessors and Retrofit Coordinators

These roles are defined under the official PAS 2035 standard for retrofit of dwellings (homes). Some sources of grant require works to be delivered to the PAS 2035 standard.

Retrofit Assessors are qualified to carry out dwelling assessments and share data with Retrofit Coordinators.  

Retrofit Coordinators are essentially project managers for retrofit, ensuring all stages of the process are delivered effectively and safely, in compliance with the PAS 2035 standard, from beginning to the end of the project. The Retrofit Coordinator has overall responsibility for every stage of the project.  

The process under PAS 2035 is focused on individual dwellings. Retrofit assessments of individual flats within a block (carried out by a retrofit assessor) may be useful as further data with which to build up a model for the whole block. Engaging a Retrofit Coordinator to advise and guide you through the whole process may also be helpful. However, not all retrofit assessors or coordinators will have experience of blocks of flats.   

Trustmark holds the database of people and companies who are registered retrofit co-ordinators and assessors.

An architect

Architects may have greater experience and expertise with blocks of flats and whole building assessments than Retrofit Coordinators who have not worked on block of flats, and architecture practices increasingly have PAS 2035-qualified people in their teams as the standard is now embedded in the retrofit industry. 

The Architects Registration Board is the official register of architects in the UK, and there are many websites that will help you find an architect in your area for different projects. 

At this stage, some of the key things to look for are: 

• A clear price to produce the review. 

• Previous experience in assessing upgrades at the whole building level for blocks of flats. 

• The ability to communicate and write reports in a way that everyone can understand – check this by asking to see reports they have produced for earlier clients. 

Technology specific experts

If your block has the option to explore low or zero carbon technologies – for example, heat pumps or solar panels – then experts in these areas may need to be procured to deliver feasibility studies.  

There are many solar PV companies that offer these services, and a growing number of heat pump specialists as this sector and technology grows. As with other experts, it will be important to check their knowledge and experience of working in the context of blocks of flats.

Calculating energy use and energy savings

Working with one or more of these experts, you could also estimate energy use and energy savings at the building level and consider typical energy use for flats in different parts of the building. The estimate of energy use may be based on a ‘typical household’, and you should not expect it to reflect any residents’ actual total energy use or energy-use patterns.  

The calculation of future energy savings may also try to take account of potential rises or falls in energy prices. The more energy prices rise, the more valuable energy-efficiency improvements become. 

You could also examine the possibility of monitoring energy use at several different flats and the whole building to improve the data and estimations. You will need to monitor over a number of months, particularly over the winter months when heating will typically be needed. Monitoring energy use is helpful to understand the current performance of the building and to identify improvement measures, and will also be helpful post installation to evaluate if intended outcomes have been achieved.

Choosing the measures that are right for your building

The key output from the review of options is information regarding what can be upgraded, how much it will cost and how it can benefit your building in terms of: 

• Energy bill savings. 

• Carbon savings. 

• Improvements to comfort.  

• Benefits to the building structure.

Ownership, Management, Permissions and Consents

In choosing options the review should consider how the building is owned and managed, and what consents will be needed for works to proceed. This will involve considering which measures are likely to be installed – wholly or in part - within the common parts of the building and which within individual flats. Legal advice may be needed as part of this process.

Regulatory compliance including for building safety reasons

The review process should also take into account any repairs and maintenance work or fire safety works that will need to happen before the retrofit project can proceed – this may be informed by an initial survey. It should also consider regulations that apply to possible measures: building regulations, fire safety requirements and local or national planning rules, including whether any local or national conservation rules apply to the building.

Considering options

What level of retrofit do you want to achieve?

There is different terminology describing the level of retrofit you may want to achieve. You might see terms such as ‘shallow’ or ‘deep’ retrofit. A shallow retrofit involves smaller-scale upgrades, achieving smaller savings on energy bills or carbon emissions. In contrast, a deep retrofit might achieve major savings in bills and carbon emissions (perhaps up to 60 or 80 per cent) but will cost more.  

Sometimes the level of ambition is expressed in terms of ‘meeting current building regulations’ – where the aim is to ensure that the homes are meeting the minimum legal standards for a new building. Some retrofit plans aim for passive house targets (see our example of Carlton Chapel House in section 4.1): ‘passive house’ denotes a set of standards involving high levels of insulation and therefore a minimal need for heating or cooling.

Presenting the options 

There are tools for presenting the different upgrade options. Different experts might use different assessment and evaluation approaches.  

See the Repowering website for an example of a simple Review of Options. 

The timescale for any improvements will be an important consideration in evaluating the options. Not all of the work has to be done upfront, and it may be appropriate to stagger some measures – for example, undertaking insulation and glazing improvements, but not installing solar PV until the roof has been repaired or replaced.  

A Retrofit Coordinator or Architect (or other expert) will advise on sequencing of measures. Many deep retrofit projects are now multi-phase projects, often with a 10-20 year improvement plan in place.

Financing installations 

Grant funding may be available to help pay for measures. See information on grant programmes and eligibility criteria in section 3.1. 

Where grant finding is not available or doesn’t cover the full cost of the improvement works, the question will then be how the remaining costs can be allocated between owners in the building. This will depend on how the building is owned/leased, where in the building the measures are being installed, the terms of leases and the type of measures planned. Legal advice will be required on these issues. Financial advice will also be required, particularly where any of the owners plan to borrow money (unsecured, or secured on individual leaseholds, or on the freehold of the whole building) to repay the costs of the retrofit.  

Leaseholders may have to contribute to the costs of the retrofit work through the service charge. In private sector blocks, the Landlord and Tenant Act 1985 sets formal leaseholder consultation requirements (the Section 20 process) as well as the right for leaseholders to participate in the procurement process where the landlord (in this context meaning anyone with the authority to enforce a service charge) is considering a contract that will incur additional charges to leaseholders, in most cases. 

To understand more about leases and leasehold law, see the government-funded LEASE Leasehold Advisory Service. Detailed information on how to follow the Section 20 process, is available from the Leasehold Advisory Service here. 

Government information on service charges is available here. 

Comparing options

Once you have two or three viable options to evaluate, you can compare each option against your budget and the priorities of everyone in the building to find the best fit.  

You can also appraise your options based on your basic budget, and grants that might be available for different technologies.  

Options reviews can be at different levels of sophistication: you may want to consider the estimated savings (in kilowatt hours per year) alongside energy prices, interest rates and other indicators. This is important for financial modelling.

The Business Case

The business case will present the decision on the different options considered. See next section.

Who is the section for?

This chapter is for building landlords and managers, including leaseholders with management responsibilities.

NOTE: information in this section is for buildings owned by a private landlord.  This section aims to provide general information on some of the considerations relevant to retrofit planning and project delivery. Building owners should seek independent advice to ensure they are compliant with all necessary regulations and take all necessary steps to deliver the project.

What does this section cover?

This section provides guidance on putting together a business case for the retrofit project and considerations to bear in mind when moving through the design and installation phase, and beyond – into day-to-day use of the retrofitted building.

Statutory Requirements

Statutory requirements around carrying out retrofit projects in blocks of flats can be complex. It is vital before embarking on detailed planning of a retrofit of blocks of a flat to seek appropriate professional advice to ensure compliance with all relevant regulations, including, but not limited to:

• The Landlord and Tenant Act 1985
• Construction (Design and Management) Regulations 
• Requirements in the Building Safety Act (particularly, but not only, important for blocks over 18m) and other Building Regulations
• Planning Regulations

Business Case

The business case brings together the information collected at earlier stages in this process: the information on benefits and the assessment of costs and benefits under different financial scenarios.

By identifying the detailed costs and estimated energy savings from the measures, and how the installation will happen, the final business case can be used to support the process of identifying procurement, contractual requirements and financing options.

The below structure for a business case for retrofit can be adapted in many cases for retrofit of blocks in the private sector. 

Source: Social Housing Retrofit Accelerator

This diagram highlights the key components of a business case. For retrofit in a block of flats, this can be considered in terms of:

• Strategic Purpose lays out the objectives for the retrofit project – this can be informed by the Initial Review assessment of why retrofit is right for the property. This can also identify how the planned project forms part of a longer-term improvement plan for the building.
• The Retrofit Actions specifies this measures that you plan to install in the building, this can be informed by an expert review of options.
• Benefits identifies the different benefits for the landlord, leaseholders, residents and other stakeholders in the building.
• Costs specifies the identified costs for the retrofit: depending on how the project is procured, these may be refined in moving from initial planning through to detailed design of the measures. 
• Financing lays out how the measures will be paid for. As well as covering how costs will be shared between owners in the building (eg from leaseholder contributions); this can include any planned grant financing.
• Procurement identifies how the retrofit project will be procured in whole or parts. There are statutory requirements around procurement processes, and this is also an area where professional advice will be needed.
• Resources identifies the resources, including staffing needed for the project.
• Risk Management identifies the plan to minimise and mitigate any risks or problems that might arise in delivering the project.

A simple example of a business plan is provided on the Repowering website.

Additional considerations for the business case

Other points to consider when preparing the business case for a block of flats retrofit project include:

• The balance of planned retrofit activity inside individual flats and across the whole building/in communal areas: Ownership, consents, regulatory requirements and financing will be different depending on whether specific measures are to be fitted inside individual flats or in communal areas of the building.
• For whole building measures, ensure issues of access to individual flats have been fully considered: Access requirements will depend upon which retrofit measures are being carried out. This will need to be agreed both with the contractor and in collaboration with the building’s landlord, leaseholders and occupants. The leases may also contain conditions on access (for example during normal hours and on reasonable notice except in emergency situations). With major projects occupants may need to be relocated for the some of the works and this will need to be considered in the business case and budget.
• Consider handover, maintenance and operational usage from the start: Consideration should be given from the business case stage on the maintenance and management that the new features/upgraded building will need and what this will require from landlords, leaseholders, managers and residents.
• Ensuring residents, leaseholders and others stakeholders are fully informed: There are statutory requirements in this area (see Section 20 consultation below). More generally, it is important stakeholders are clear on what the project involves, any costs that will fall to them, and how it will affect them. There should be a plan for keeping them informed of progress from the Business Case stage. Involvement of a Leaseholder or Resident Committee – if there is one – is vital from the start.

Setting and measuring outcomes

The detailed business case should include a full statement of intended outcomes of the project. This can build on the information collected in the initial review document where stakeholders specified what benefits they think the retrofit will bring and be based on the information collected about the block.

Outcomes for building performance will come from the review of potential upgrades. They may be set in terms of target EPC ratings or strategies for reducing the energy demand in properties (measured in kWh/m2/year). Broader goals may be relevant. For example, outcomes may include other improvements: “redecoration of all common areas and widening of a front door and addition of a ramp, within two years.”

Outcomes should be specified in the business case that are measurable, and may be used to prepare procurement documents. In other words, results could be written into the contracts and targets set with suppliers and contractors. 

Measuring outcomes

It may be possible to install a monitoring system to allow residents to view their energy data before and after the retrofit. This would mean not just relying on an assessment or model to predict the results but also having data to check the results. This could include:

• Measuring heating energy and hot water use (as well as gas and electricity) by installing heat meters (or a Smart Heat Interface Unit (HUI), if using communal heating).
• Monitoring indoor and outdoor temperatures.
• Monitoring indoor humidity or other air quality indicators.
• Combining different data to get an in-use real performance metric for the building.

There may also be an opportunity to include meters that show the ‘whole-building’ energy consumption – where each flat is anonymous – and sub-metering for common areas.

Budget

Considerations when preparing the budget include:

• There are reduced rates of VAT on some energy-saving building measures. Ensure the budgets and business plan have been reviewed by an accountant to consider what level of VAT will apply to the different equipment and materials being installed, and whether any further tax allowances may apply to the work and the measures to be installed.
• Can the costs be shared with any other works being considering?
• Including inflation. Current levels and forecasts are published by the Office for National Statistics. Construction costs may increase at a higher rate than average inflation and it may be appropriate to use a higher rate to reflect that.

Budgets for construction projects typically include a ‘contingency’ allowance, which is to anticipate any underestimates in cost. Ideally the contingency won’t be used, but it reduces the risk of the project stopping if a there is a greater than expected rise in costs. The appropriate level of contingency will depend on the complexity, scale and duration of the project, but levels of 8-12 per cent are commonly seen.

Section 20 consultation

Leaseholders may have to contribute to the costs of whole building retrofit work through the service charge. The Landlord and Tenant Act 1985 sets formal leaseholder consultation requirements as well as the right for leaseholders to participate in the procurement process where the landlord (in this context meaning anyone with the authority to enforce a service charge) is considering:

• Works that would result in additional charges to leaseholders of over £250 per leaseholder, or 
• A new contract for services of over 12 months duration that would result in additional charges to leaseholders of over £100.

Such works or contracts are known as ‘qualifying works’ and ‘qualifying long-term agreements’.

Detailed information on how to follow the Section 20 process, is available at the official Leasehold Advisory Service here.

Considerations through the delivery of the retrofit

Irrespective of the manner the project is procured and delivered, some of the key considerations that should be considered include ensuring that the following is in place.

• A delivery plan: This is not only about the construction work but also the experience of stakeholders. The delivery plan should aim to ensure that the process is clear to stakeholders – landlord, residents, leaseholders, non-resident leaseholders, and neighbours – and information is communicated at the right time and in the right way. This should allow all stakeholders to understand roles and responsibilities for different parts of the work, as well as to understand linkages between elements of the project.
• Clear project timeframes: The contractor should have proposed an installation method statement and timeframe for the installation within their tender. Make sure that everyone is aware of this, including leaseholders or tenants whose homes are being retrofitted. Check for pinch points when there may be acute disruption or delays as seasons change. Check whether the timing looks realistic and make sure that enough time has been planned for the handover stage – this often gets rushed and is a key moment to make sure residents understand how to get the best out of any new retrofit measures.
• Certainty around statutory compliance through the design and delivery phase: Multiple regulatory  requirements apply at planning, design, delivery and handover stages. Professional advice should be sought on identifying these requirements and an agreed plan in place with the retrofit design and delivery team to ensure compliance.
• A thorough risk register for the delivery phase: Key risks may include going over budget/time, or unexpected circumstances such as structural issues. Risks should be highlighted, and thought should be given to how they might be mitigated or overcome.
• A clear plan for handover (see below): Ensure that maintenance and ongoing operation is thought about at the planning design stage, so that even before the installation begins there is an agreed handover and operational plan to support owners, building managers and residents in the day-to-day use and maintenance of the new measures/upgrades.

Handover and Maintenance

Well-maintained and operated energy systems will be more likely to deliver the reductions in energy demand and carbon emissions that the retrofit project aimed to achieve. More importantly, good maintenance and operation of these systems will help support residents’ health and wellbeing, for example by ensuring that living spaces are kept at the temperatures requested, and bathrooms and kitchens are adequately ventilated.

Consideration can be given to including maintenance support as part of the contract with the installer. Further steps to ensure that maintenance happens properly include ensuring the installer hands over the installed services to the team that will be responsible for managing and maintaining the building/system, to users - both resident leaseholders and tenants and to the owner/s.

Ensuring an ongoing ability to maintain the block: ensure the building management team will have the knowledge and skills to maintain new equipment properly. If there isn’t a building management team, try to identify a technically-minded leaseholder or other person involved in the building management who can oversee and arrange required maintenance on an annual and as-required basis.

At the end of the project, the building manager will also want to set out clear expectations with leaseholders and tenants. The building manager will usually be the first port of call for reporting faults or issues with their energy systems. The manager should have systems in place to support leaseholders and tenants. These measures could include:

• Clearly written online and printed instruction manuals available both in English and relevant minority languages and formats, as required.
• Accurate log-keeping of issues and system failures.
• Opportunities for communication and meetings with all stakeholders.

Who is this information for?

Landlords, managers and leaseholders of private sector blocks of flats.

What this section covers

This section provides information on grants or funding that may be available to support retrofit energy efficiency measures, as at November 2023. No warranty is provided as to the accuracy of this information – see Limits and Disclaimers.

Key Points

The availability, rules and eligibility for grant schemes change regularly. This information is intended to provide an indication of the type of funding that may be available and is not to be relied on in making any decisions when planning retrofit projects.

The focus of the available grant funding we describe below is on individual properties (ie flats). However, some grant schemes increasingly make provisions for measures to be installed across multiple homes in a block of flats. So applications will usually need to be led by individual leaseholders, but – depending on the grant scheme there may be opportunity to discuss building wide measures.

Councils often bring together funding from different sources to deliver energy efficiency programmes for homes in their area. Speak to your council, particularly if you want to consider a building wide programme for your block.

Grant schemes

Boiler Upgrade Scheme

Source: UK Government funding via the Department for Energy Security and Net Zero (DESNZ)

Scope: Replacement of gas, oil or electric boiler/heating with air or ground source heat pumps (funding is also provided for biomass boilers but is not discussed below, as less likely to be relevant to blocks of flats).

Air source heat pumps supported under this scheme must be air-to-water heat pumps (air to air heat pumps do not qualify).

Ground Source Heat Pump support includes support for heat pumps installed using a shared ground loop system (where one ground loop provides heat for heat pumps installed in multiple homes).

Value: Subsidy of £7,500 per property for an air source heat pump or a ground source heat pump.

Eligibility: Installation must be undertaken by an installer registered by the Microgeneration Certification Scheme (MCS); most properties must have an EPC which does not have outstanding recommendations for loft or cavity wall insulation.

Application process: Request a quote from an MCS-registered installer; if the quote is agreed they will submit the grant request to Ofgem, who will then contact the client directly to confirm you approve the quote and installation. The value of the voucher will be deducted from the invoice you pay to the installer.  

Exclusions: Confirm eligibility by checking the official information and guidance listed below. You can also contact the scheme administrator, Ofgem, for further advice. Most new-build properties are not eligible (self-build properties can be eligible). Social housing is listed as excluded from eligibility but Ofgem guidance on the Boiler Upgrade Scheme for property owners states that “Properties that have undergone a sale through the “Right to Buy” scheme are not classified as social housing”.

More information: See government guidance and guidance from Ofgem, the scheme administrator.

Contact the Boiler Upgrade Scheme.

Energy Company Obligation (ECO)

Note: this programme is often called ECO4, as it is the fourth phase of the ECO programme.

Source: Energy Suppliers are required to run ECO programmes by the government. Energy suppliers arrange and pay for some or all of the costs of the installation of energy-saving measures in homes.  

Scope: Heating, insulation and ventilation improvements, subject to multiple eligibility criteria and allocation ‘caps’ for different types of improvement measures. The measures offered to a property are at the discretion of the energy supplier.

Value: The amount available per property is at the discretion of the energy supplier and measures will be directly installed by the supplier’s installer partner. Householder/home owner contributions may be requested towards the cost of the works.

Eligibility: Properties with an EPC rating of D or below; the support is targeted at those in social housing, on a low-income or fuel poor households. Decisions about installing measures in any particular property is at the discretion of the energy supplier.

Exclusions: Properties with an EPC rating of A, B or C though rules may allow ECO funded insulation to blocks that include some higher-banded flats.

Notes for flats: Funding is focused at the property level rather than the whole-building level; however, it may be possible to combine works to allow for insulation improvements across a block of flats. The rules for the latest round of the ECO programme include some new conditions that make it easier for works on whole blocks to proceed.

How it works and how to apply: Each energy supplier decides which homes they want to work with and which measures they will offer, within the scheme rules.

How to apply:

There is not a single application route.

• Contact energy suppliers - Ofgem provides a list of ECO-obligated energy supplier contact details
• Contact the housing team of the local council, who may be involved or aware of ECO programmes.

Alternatively, energy suppliers or their partner installer companies may approach residents or owners.

Great British Insulation Scheme

Like the ECO scheme, the Great British Insulation scheme is a government scheme delivered and funded by energy suppliers.

Scope: Insulation improvements, including cavity wall insulation, solid wall insulation, loft and floor insulation. Under the scheme, one measure is usually provided per home.

Eligibility: Homes with an energy performance certificate rating of below C.  

Household eligibility for support under the scheme is complex: some of the support is targeted at low income and vulnerable households, though there is also more general support available for households living in properties with a council tax band of A-D.

Ofgem states that, “eligibility for the Great British Insulation Scheme does not guarantee that an energy supplier or installer will decide to install energy-efficiency measures in your home.”

Value: The amount and measure available per property is at the discretion of the energy supplier and measures will be directly installed by the supplier’s installer/delivery partner. Householder contributions may be requested towards the cost of the works.

Notes for flats: As with ECO, funding is focused at the property level rather than the whole-building level; however scheme rules do include flexibility to make it possible and easier for insulation improvements to be applied to multiple flats across a block.

How to apply:

The UK Government provides a referral service to help home owners contact energy suppliers to express their interest in the scheme:

Speak to  your local council who may be involved in schemes

For more information, see government advice. 

Home Upgrade Grant

Source: The Home Upgrade Grant (HUG) Scheme is government funding provided to councils to retrofit properties.

Scope and notes for blocks of flats: The Home Upgrade Grant (HUG) is government funding provided to councils to retrofit properties that do not have a connection to the gas grid, providing insulation and clean heat (eg heat pump) installations. This may be particularly relevant for flats which are more often electrically heated than single family houses.

Value and eligibility: The Home Upgrade Grant is for home owner occupiers (ie people who live in and own their home). Households are are usually required to have a household income of less than £31,000, though the income threshold can vary. Where households participate in the scheme, the council will organise and pay for the works.

Application process: For the Home Upgrade Grant, homeowners can see if they may qualify and if their council is running a HUG programme via a central government service. This site also provides more information on the scheme.

For more information, see government advice. 

Speak to  your local council who may be involved in schemes, particularly if multiple flats in the building may qualify.

Who is this information for?

Landlords, managers, leaseholders with management responsibilities, of private sector blocks of flats. Retrofit professionals helping plan a retrofit project for blocks of flats. This section incorporates text adapted from the Social Housing Retrofit Accelerator.

What this section covers

This section provides information on planning rules for retrofit measures. It is vital to identify local planning constraints, build them into the plan for retrofit, and comply with planning and regulatory requirements.  

Planning need depends on the type of property, the measures to be installed/changes to be made and the site location. Blocks of flats are more likely to require planning permission for retrofit works than houses.  

Planning rules are only part of the picture in terms of regulations that might affect how a flat or block of flats can be retrofitted. It is important to consider Building Regulations which apply to many upgrades to the interior or exterior of existing buildings as well as other statutory requirements, such as the Party Wall Act and fire safety rules.  

Before reaching this stage, it is vital to be clear on all consents and agreements that need to be in place from all parties with an interest in the building – landlord, leaseholders, mortgage lenders, residents etc. 

This section should not be used as the basis for any decision-making or investment: it is not a substitute for information from the Planning Portal, for planning guidance from the council and advice from a professional planning consultant. See Limits and Disclaimers.

Key steps to take

Check if the works are permitted development: Some types of retrofit work fall under Permitted Development Rights and do not require planning permission. However, these rights may not automatically apply, so it is vital to check. 

Check if the buildings are listed or in a Conservation Area: If properties are listed, then it is necessary to obtain Listed Building Consent for most work that is carried out. If the properties are in a conservation area, then some permitted development rights may not apply. 

Check local planning conditions: Every local authority should have a local development plan (or local plan). It is important to check local planning conditions at an early stage of the project to identify any approvals that might be needed. If a retrofit project crosses local authority boundaries, it will be necessary to check multiple local plans, as they will vary. 

Talk to the planning authority/authorities: An early conversation with the local planning team(s) can provide vital information on what is required and the process for securing permissions. It also helps avoid any surprises later in the process and having to re-submit an application, which costs time and money. 

Business plans should allow time and resources for the planning process: Planning permission can take 8-16 weeks to work through the approval process; if a project is grant-funded within a very tight timeframe, then this may preclude some works from happening. Planning applications will also carry costs and these will need to be included in the business plan. 

Make sure the right team is in place: Consultants may be required to assist with planning applications as most local authorities have strict requirements on the information that needs to be submitted as part of the application. The consultants required will depend upon the project but they may include an architect, planning consultant, heritage consultant and ecology consultant. 

Make sure all permissions are in place before starting on site: All necessary planning approvals must be in place before the retrofit works start on site. Where projects that proceed without permissions, owners could be asked to “undo” work, which will cost time and money and damage reputation. If the works affect a protected historic building, this could be a criminal offence. 

Success factors

Start early - it is a good idea to identify any potential planning issues as soon as possible. Steps should be taken to find any problems before getting too deep into the project and avoid later delays and difficulties. Advice should be sought from the relevant local authority’s planning team to confirm conclusions. 

Do not make assumptions – Some retrofit measures are counted as permitted development and, in most cases, do not need planning permission. The important word is “some”. Some local authorities have set specific rules around what is allowed without permission. It is vital to check the local plan for the local authority concerned. 

Align with the local plan – When applying for planning permission, it’s important to show that the project contributes to the aims and objectives of that plan. In some cases, this is fairly clear: if the local authority has a commitment to carbon reductions (such as a net zero target), it should be possible to demonstrate how the retrofit will help cut emissions. Other considerations in the local plan could include design guidance to reflect local architectural heritage or wider local or community benefits. 

Plan for planning – the planning process can take time and feel frustrating. It is crucial to think about planning to manage the expectations of all stakeholders and to set a realistic timetable for procurement and delivery of the retrofit works. 

Manage residents and other stakeholders’ expectations – letting all stakeholders know that a planning application needs to be submitted for works to the building. Residents might need to give access for assessments to their homes as part of preparing the application. Letting them know about the process will also avoid them getting surprised by seeing a planning notice up or being asked questions by neighbours who have received a letter about the proposed works. 

Deep Dive: local planning

All UK local authorities are required to have a local development plan (or local plan) that sets out their building development policies and designations for different geographic areas. These local plans can exclude some Permitted Development Rights. Many local authorities will also have Supplementary Planning Documents (SPDs) providing specific guidance in relation to certain projects such as those in Conservation Areas. 

In addition to the national legislation for listed buildings, there may be locally listed buildings which are identified in the local plan due to their architectural or historic interest. 

There are also species which are protected by law, such as bats. If there is potential for disturbing protected species as part of the works (for example, works to the roof/within the loft where bats may be present) then mitigation measures may be required. Many local authorities will provide biodiversity checklists which will indicate whether protected species may be affected. There may be a requirement for a preliminary ecology appraisal or more in-depth ecology surveys to be submitted as part of any planning application. 

Most local authorities will encourage submitting a pre-application enquiry which is a way of receiving formal advice on the proposed scheme. There is usually a fee involved and it can take around 4 weeks to receive advice. Pre-application enquiries are confidential so can be useful in the early stages of the project prior to any resident engagement. 

Deep Dive: Permitted Development Rights

Permitted development rights allow certain building works and changes of use to be carried out without the need for a full planning application. To comply with Permitted Development Rights an installation (or other change to the building) will still need to meet certain requirements, for example in terms of its size and position on the buildings. 

As the Planning Portal website advises, “The permitted development rights which apply to many common [building upgrade] projects for houses do not apply to flats.”  

Further, councils may withdraw Permitted Development Rights in certain circumstances for particular buildings or to buildings in an area. For example, an Article 4 direction is applied to an area to withdraw the PDRs applying to certain measures or changes of use to the buildings in that area. It is therefore vital to confirm with local planning authorities that PDRs apply in relation to any specific measure or change to any specific building. 

PDRs do not apply in many cases where buildings are protected for reasons of history, architecture, or to protect the character of an area.  

Where a building is listed, any action taken without planning permission, where this is required, is a criminal offence. Retrofit for listed buildings can be a complex area. 

Building owners will likely need to appoint a heritage consultant to assist with the application if the building is either listed (Grade I, II* or II), locally listed, a scheduled ancient monument or is within a conservation area. 

Table of low-carbon retrofit measures and permitted development rights

Read “Deep Dive: Permitted Development Rights” before using this table. The table below provides information about whether Permitted Development Rights can (but may not for any particular building) apply in relation to measures installed in blocks of flats. Note that this provides general information based on a review carried out in Summer 2022; no guarantee is provided as to accuracy and the information provided may not apply to any particular building.

*Content in this cell adapted or reproduced from the Town and Country Planning Order 2015 available at legislation.gov.uk Contains public sector information licensed under the Open Government Licence v3.0. 

Further information and resources

The Planning Portal website - a joint venture between the Government and a private company – is a website providing information on planning rules. See particularly the Planning Portal guidance on Flats and Maisonettes here: Flats and maisonettes. 

Who is this information for? 

Landlords, managers and leaseholders of private sector blocks of flats. 

It is important to remember when reading this section that the materials appearing in this Toolkit do not constitute legal advice and are provided for general information purposes only. See Limits and Disclaimers.  

What this Section covers 

This section covers issues relating to terms of leases relevant to retrofit measures, and to arrangements by which leaseholders may pay for upgrade measures.

Terms of leases

A lease will impose on the landlord certain obligations to maintain the building and keep it in good repair and condition. In order to do so, the lease will also grant the landlord express rights to do so (such as the right to access individual flats, to change common services such as pipes and cables, and to erect scaffolding). If work needs to be done within an individual flat, the landlord has the right to require access and can ultimately ask the court to grant an injunction if necessary to enforce this right. Leaseholders do not have these rights. It may be difficult for them to gain access or even a breach of their lease if the leaseholders did so unilaterally. 

The lease will also provide for the leaseholders to pay a service charge to the landlord to cover the costs of carrying out its obligations. A well drafted lease will also provide for a reserve or sinking fund for future works. Key to funding and financing retrofit measures will be to determine whether and how they can be financed wholly or partially through the service charge and whether any reserve or sinking funds that have been built up can be applied. This will depend on the provisions included within the lease, the particular circumstances in which the work is being done and the nature of the retrofit measures that are being planned. 

Finally, the landlord has the right to enforce the leaseholder’s obligation to pay the service charge (including any advance payments and sums to create a reserve or sinking fund). This includes the right to “forfeit” i.e. to end the lease if the leaseholder fails to pay. There are various statutory provisions in place which protect leaseholders (and any lender with a mortgage on the flat) from losing their lease (there are a number of statutory limitations on a landlord's right to forfeit a long residential lease that restrict the right to forfeit a lease of residential property (premises that are let as a dwelling); a landlord will usually have to go to court and bring forfeiture proceedings in order to forfeit the lease),  but ultimately it ensures that the costs can be collected.  

Issues to consider 

Leases typically require the landlord to keep the structure of the building, the common parts and the plant and equipment in the building in good repair and condition. The obligation kicks in if the building or plant has deteriorated. However, the landlord may not be limited to replacing like with like. So, for example, if old single glazed windows in a building are in a poor state of repair and the landlord decides to replace them, it may be able to install double glazing and, provided that it follows the procedure for consultation and tendering under the Landlord and Tenant Act 1985, it can expect to recover the cost through the service charge. This is the case because replacement windows will often need to be double glazed to comply with current building regulations. In these cases, it’s likely that the costs could be recharged through the service charge. 

Conversely, a common heating system may be functioning properly but not very efficiently and causing higher energy bills to leaseholders and so the landlord may wish to replace it with one that is more energy efficient. Unfortunately, such work would not fall under the landlord’s repairing obligation. It would, only if, for example, a gas-based communal heating system had irretrievably broken down that the costs of the low carbon replacement could be recovered through the service charge.  

In such circumstances, the landlord would need to rely on a provision in the lease that allowed for improvements that go beyond maintenance and repair. Leases originally put in place by local authorities1 do more often include a provision allowing the landlord to make improvements and reclaim the costs through the service charge. Where buildings have these sorts of leases, undertaking low carbon upgrade works is much easier, although consideration will still need to be given to whether leaseholders can afford the resulting increase in service charges. 

Elsewhere it is relatively unusual for a lease to allow the landlord to carry out improvements. In certain situations, this is advantageous to leaseholders as it protects them from landlords undertaking substantial building enhancement works with no benefit to leaseholders and at their expense. However, the disadvantage is that unless everyone agrees (and it may not be practical to secure agreement) reasonable upgrade works that could save leaseholders money - such as insulation - cannot be made through the normal mechanism by which the building is kept in good repair and condition. The cost of the works could not be included in the service charge and the landlord would not have rights of access to flats. If the landlord decided to proceed anyway, it could be challenged by a leaseholder in the First Tier (Property Chamber).    

One possible way to overcome this would be for the leaseholders to vary the leases to permit the landlord to carry out improvements. This could be done with either a deed of variation or a supplemental deed. It could be a general variation or one that is limited to a specific project. This is not a complex document but it would require the agreement of 100% of leaseholders and any lenders, and in larger buildings this may not be practical.  

Arrangements by which leaseholders may pay for retrofit measures

Arrangements under which leaseholders pay for upgrade measures can be of broadly two types: 

1. Payments out of the building’s reserve and/or sinking funds. 

A well drafted lease will contain provisions for a reserve and/or a sinking fund as part of the service charge. A reserve fund is designed to ensure that landlords prepare for and manage general future expenditure such as on maintenance and repair. A sinking fund is similar to a reserve fund but it differs as it is money allocated for a specific purpose. Not all leases are so well drafted that they have such provisions but if the block has a reserve and/or sinking fund it may be possible to use this towards the cost of energy efficiency measures. Alternatively, the  landlord could choose to create such a fund for this specific purpose. If the cost of the works will exceed £250 per leaseholder, the landlord will also need to follow the requirements of section 2 of the Landlord and Tenant Act 1985. (see  the Leasehold Advisory Service’s information on Section 20). 

However, this will only be an option where paying for the cost of the works is recoverable from the leaseholders under the terms of the lease [See section Terms of Leases above]. 

2. Voluntary additional contributions by leaseholders. 

In a small share of freehold block, where all leaseholders are directors of a company that owns the block, this may be a viable option for paying for the upgrades.  For one-off payments the leaseholders would simply agree between themselves to make additional payments into the company to cover the costs.  They could agree to set up and use a sinking fund to do this. They could also enter into a deed of variation or supplemental deed (see above) recording the agreed terms. This approach is, however, harder to implement in a situation where leaseholders are not also the co-owners of the building, and/or where leaseholders do not have an amicable relationship with each other. In such circumstances they would need to put in place a contract that would set out the terms of the formal legal agreement between them. This should ideally be drawn up by a solicitor.  

Can leaseholders afford the payments? 

Of course, regardless of the legal issues and practicalities around making the payments, the bigger issue is whether leaseholders are able and willing to pay for the upgrades. Leaseholders are likely to want to first investigate potential grants or other financing options before agreeing to contribute.   

Further information and resources

To understand more about leases, and freehold/leasehold law the best starting point should be the Leasehold Advisory Service: Home - The Leasehold Advisory Service (lease-advice.org) 

Information for this case study has been provided by Anne Thorne Architects, including their work with the Passivhaus Trust case study “Carlton Chapel House EnerPHit”.  The detail we provide in this case study has been reproduced with the permission of Anne Thorne Architects and Passivhaus Trust.  We are also grateful for input from North Camden Housing Co-operative.

North Camden Housing Cooperative: A highly energy efficient retrofit

The Block

Carlton Chapel House (Kentish Town, North London) – a three-storey block with 15 flats

 Figure 1: Before (left image) and after (right image) of the retrofit

Images credit: Anne Thorne Architects, left image from Passivhaus Trust case study, right image from Arctic Street case study.

Ownership and Residents

North Camden Housing Cooperative (NCHC) is a not-for-profit and fully mutual Housing Cooperative (only tenants can be members). NCHC is run by a management committee, democratically elected by the residents to manage the day-to-day operations and future plans. Carlton Chapel House is managed by the Cooperative.

In total, the cooperative has 106 units across 28 properties. The organisation’s assets and operations helped unlock third-party private finance.

It is important to note that a housing cooperative is distinct from all forms of ownership. In the privately owned context, it is most similar to a ‘share of freehold’ situation.

Why retrofit?

NCHC were motivated to retrofit because of cold, condensation, mould growth and fuel poverty – all of which were exacerbated by rising fuel prices, making it harder for residents to sufficiently and properly heat their homes to remedy these issues.

An environmental design to passivhaus standards was chosen following feasibility studies and options appraisal. Passivhaus is a set of standards that involve high levels of insulation and ventilation, so that little additional heating or cooling is required to keep the property comfortable. This retrofit was carried out to the EnerPHit standard – the Passivhaus standard for retrofit projects. This option was chosen as it would future proof the building for the next 60 years.

Project objectives

• Improve energy-efficiency and living conditions – create warm, comfortable living spaces that were well ventilated but not draughty.
• Reduce bills by improving energy-efficiency – measures such as external wall insulation and triple-glazed windows that would improve energy-efficiency, therefore reducing energy demand and bills.
• Reduce emissions – Switch from gas to direct electric heating and hot water, and install photovoltaic (PV) panels with any excess used to heat hot water. Direct electric heating can produce fewer carbon emissions than gas heating, and if that electricity can be generated from renewable sources, such as from the sun via PV panels, then operational carbon emissions are eliminated.
• Improve the property – five bedsits were converted into one-bed flats, the deck access enclosed, and main entrance improved.

Finance

The project cost was £1.4m (see Passivhaus Trust case study). Due to the assets and operations of NCHC, they were able to secure finance through a loan on their other owned assets.

Selecting a project manager/contractor

An architect was appointed as project/contract manager. The design team was directly appointed by the client (NCHC) and a full-stage design and specification with a detailed survey of construction, structure and services, was undertaken.

The construction team were appointed through a two-stage tender process, appointed under a traditional JCT contract, where the client retained risk.

The successful management of the construction tendering process and onsite procedures are replicable lessons for future projects. The strong relationship between architect (project manager), design team, contractor, subcontractors and client (NCHC) was key to the success of this project. Architects were on site weekly and had regular consultations with NCHC, contractors and sub-contractors. This relationship built trust and confidence on all sides, and helped overcome challenges as they arose during the project.

The members of the project team were as follows:

Client: North Camden Housing Co-operatives advised by consultant Adrian Buffery 

Contractor: HA Marks 

Architect: Anne Thorne Architects LLP  

Quantity Surveyor: Peter Gittins Assoc  

Structural Engineer: Corbett & Tasker 

Services Design: Alan Clarke

The retrofit measures

• External wall insulation (EWI).
• Triple-glazed windows.
• Improved ventilation and moisture strategy with improved air-tightness and mechanical ventilation with heat recovery (MVHR).

• Switch from gas to direct electric heating and hot water.
• PV panels, with any excess electricity used to heat hot water.

Other, non-energy improvements were also made, for example minimising noise penetration between the flats.

There were also improvements to rented flats through the conversion of five bedsits into one-bed flats.

Benefits and outcomes

Post-occupancy evaluation reveals that as well as improved energy savings and warmth, residents are reporting better air quality.

Noise problems are reduced by removing the shared flues and installing triple-glazing.

“The energy consumption of the flats reduced significantly, with heating and hot water bills reduced by up to 90 per cent for tenants...This has meant that they’re able to live in a warm, affordable home – with fuel poverty no longer a concern. What’s more, as a co-op, we know that we’ve made the right choice for the planet as well.” – North Camden Housing Coop quoted in Passivhaus Trust Case Study.

Challenges

• Residents were temporarily relocated for flats to be taken back to the bare walls, with plumbing, electrics, and plaster stripped out.
• Technical challenges, particularly in making the property hit a strict air-tightness target (the Passivhaus approach minimises air flows from cracks and gaps, with fresh air coming in from planned ventilation units). In this case, air penetration from cavity wall and hollow plank construction was successfully dealt with and below target of 1 air change per hour achieved.
• Delivering on time and on budget.
• Securing finance and improving units to increase value to help cover costs in the long run.

Information for this case study has been provided by John Gilbert Architects, including their work with the Passivhaus Trust case study “A retrofit template for hard-to-heat tenement homes“. The detail we provide in this case study has been reproduced with the permission of John Gilbert Architects, Passivhaus Trust and Southside Housing Association, the owner of the building. Photos of completed project have also been provided by Tom Manley Photography.

A complete refurbishment of an empty block

The Block

A pre-1919 ‘tenement’, four-storey block, with eight one-bed flats.

The property is a traditional sandstone ‘tenement’ (Scottish term for medium rise flats), with a single common stairwell. One third of a larger tenement block, the property was essentially as originally built.

Figure 2: Before (left) and during roof insulation installation (right)

Image credit: John Gilbert Architects, from Passivhaus Trust case study, ”A retrofit template for hard-to-heat tenement homes“, “A retrofit template for hard-to-heat tenement homes“.

Ownership and Residents

Social Housing (Southside Housing Association)

The building was vacant and had been for two years prior to the major works, and in need of structural repairs. The need to carry out these repairs was a key reason to justify the retrofit – it was the ‘trigger point’.

When complete, the flats will be let as social housing.

Why retrofit?

Due to urgent and necessary structural repairs, it was cost effective to add a retrofit works programme to the other refurbishment works. The tenement had been vacant for two years due to its dilapidated condition.

The building, a classic pre-1919 Scottish tenement, was of an age, construction type and condition that made it energy inefficient. Residents would be at risk of fuel poverty due to the high levels of energy consumption, while not finding solutions for this common type of housing would cause major challenges for the achievement of Scotland’s net zero ambitions.

The focus of the work was to demonstrate a comprehensive, whole building, ‘deep’ retrofit, to serve as a demonstrator for the retrofit of traditional buildings.

This project was delivered through a number of partners – delivery, learning and financial – led by the building owner (Southside Housing Association) and main funding partner (Glasgow City Council). The timing was right for all parties:

• Full funding was arranged and organised.
• With a clear goal in mind – deep retrofit for this building but also as an example of what can be done. All partners signed up to the end goal.
• Vacant building – no need to convince a range of stakeholders.

Project objectives

• Adding retrofit to required structural repairs – making the most of already necessary structural works.
• Minimise energy use and maximise comfort – using a fabric first and comprehensive approach.
• Future-proof the building – ensure the building is ready for a low-carbon future and can provide future residents with comfortable and warm homes. With installation of further renewables or connection to a local district heating network, this property could achieve net zero.
• Wider social aims – reduce fuel poverty, improve housing, provide example of comprehensive adaptation of historic buildings.

Finance

£1,091,000

Funded by:

• £517,000 – Southside Housing Association (building owner)
• £445,000 – Glasgow City Council
• £129,000 – additional grant funding from the Scottish government.

This cost represents the total costs for the whole refurbishment. It was estimated that the energy-efficiency elements of the works programme amounted to roughly £40,000 per flat, a total of £320,000. (Passivhaus Trust, case study, A retrofit template for hard-to-heat tenement homes).

It should be noted that void costs and relocation costs are not included in this total figure. Any future consideration for carrying out work of this type should consider these extra costs.

This project benefitted from the building owner being a social housing provider and the support of the Scottish government to demonstrate what can be done at this type of building.

Privately owned blocks of flats will need to find other sources of finance but could also reduce costs by choosing a package of works that was less comprehensive than included in this demonstrator project.

Procurement/contract management route

Appointed an architect (John Gilbert Architects) as project/contract manager.

A variety of partners were hired for the delivery of these works, led by the project architect chosen by Southside to manage the contract. The desire for this project to be a demonstrator and example for future retrofits of similar buildings meant there was a thorough evaluation process led by research partners too.

Contract management was effective as there was a clear goal in mind, with all partners and stakeholders on board. It also helped that the property was empty and therefore it did not need mutual agreement between a number of residents and leaseholders.

The Retrofit

This project is an example of a deep, holistic and comprehensive retrofit.

• Necessary structural repairs.
• Internal and external wall insulation – heritage consideration meant the project needed this hybrid approach.
• Triple-glazed timber windows – acceptable for heritage requirements, and carefully integrated into the air-tightness and insulation strategies.
• Mechanical ventilation and heat recovery with summer bypass.
• First floor joists removed from walls to avoid moisture risks and decay, and allow for continuous insulation and airtightness.
• Waste water heat recovery systems installed to capture and recycle heat from baths, showers and the kitchen sink.
• Layout altered to provide better flexibility and accessibility.
• Air Source Heat Pumps (ASHPs) installed on four flats on the first two storeys – the research project will collect data about how the ASHPs compare with the upgraded gas boilers installed in other flats.

(Retrofit measures for this project taken from the Passivhaus Trust, case study, A retrofit template for hard-to-heat tenement homes)

Benefits and outcomes

This example demonstrates the benefit of identifying a ‘trigger point’ – adding retrofit works onto otherwise necessary maintenance and repair. This provides an excellent opportunity to significantly reduce costs and complexity of an otherwise retrofit-only project.

Due to Covid, construction finally began in April 2021. The evaluation is scheduled to complete in 2023. It is estimated that the results go well beyond the Energy Efficiency Standard for Social Housing (Scottish energy efficiency standard) and demonstrates what it is possible to achieve.

Challenges

Planning constraints: Installing external wall insulation (EWI) was challenging due to heritage and planning constraints. Adding EWI to the front of the building was not possible, for example.

Practical concerns: This was a deep retrofit and required substantial construction works, with the need for scaffolding which caused disruption. All flats were unoccupied which made this level of disruption easier to manage. Doing this work with occupied flats would have been challenging to organise and would have needed residents to move out for a part of the works. This project also demonstrated that where there are multiple parties (i.e. residents and /or owners), good communication is crucial (Passivhaus Trust, case study, A retrofit template for hard-to-heat tenement homes).

Photos of the completed retrofit; front exterior and interior of a flat. Credit for both photos: Tom Manley Photography.

​

Information for this case study has been provided by Energiesprong and the Lancaster West Neighbourhood Team. The Royal Borough of Kensington and Chelsea crated the Lancaster West Neighbourhood Team as a new organisation to address the need for refurbishment at the Lancaster West Estate. The detail we provide in this case study has been reproduced with the permission of Energiesprong and the Royal Borough of Kensington and Chelsea (RBKC). The case study was prepared in early 2023.

Delivering homes with very low energy bills

This case study is of a retrofit project that is currently ongoing, set to be completed by the end of 2023. The case study demonstrates a wide range of improvement measures that have been chosen to achieve (or get as close to) net zero; attempting to eliminate carbon emissions as much as possible. Of particular relevance and interest to landlords, leaseholders, and building managers will be the Energiesprong approach to installing insulation (offsite manufacturing), communal Air Source Heat Pumps installed on the roof to replace gas boilers, and the challenges of planning, utility supplies and budgeting that the project has had to overcome.

The Estate and the Block

Treadgold House is located on the Lancaster West Estate in North Kensington.  There are 795 homes across the estate, the majority of which are flats. The Lancaster West Estate is also the location of the Grenfell Tower tragedy where 72 people lost their lives in June 2017. Following this, there was a recognition of an urgent need to address repairs at estate, and to put residents at the heart of a refurbishment to create a 21st century model estate.  

To do this, a wholly new organisation was set up called Lancaster West Neighbourhood Team (LWNT).   RBKC and LWNT then committed to a new vision and ten core principles for the refurbishment, which make up a complete resident co-design approach to refurbishment. The ambition is to create a 21st century estate and carbon-neutral homes by 2030.

Treadgold House was built in the 1960s and was the first post-war building in the Estate. The block has four storeys and consists of 38 homes – a mix of studios, one-bed flats, three-bed flats and maisonettes.

Ownership and Residents

The block, like the estate, is owned by RBKC. It will be the first council-owned housing block to go carbon-neutral and be refurbished to Energiesprong performance standards. Energiesrpong is a performance standard and funding approach to whole house retrofit, that makes use of offsite manufacturing and pre-assembled ‘energy pods’ to achieve net zero homes. The approach was developed in the Netherlands and is now being adopted in the UK.

The commitment to co-design means residents are given an active role in each stage of the refurbishment and need to vote in favour of any designs and works to be completed.

For the Treadgold project to go ahead, they required a simple majority of 51% of residents over 16 years of age to approve the project. When the consultations were finalised, 96% of residents at Treadgold House approved the retrofit works.

Why retrofit?

For RBKC, this is part of their target to decarbonise all council housing stock as far as possible by 2030.

The council has an ageing building stock that is difficult to retrofit. Treadgold House is a suitable choice to trial a deep retrofit which can then be scaled up to the wider estate and beyond.

The work at Treadgold House will also form part of other sustainability proposals that the council wants to develop and deliver to meet its commitment to be carbon neutral by 2030.

For residents, they wanted their concerns at the block and estate to be addressed:

• Security and access (including lift maintenance issues).
• Condensation and mould.
• Underused external space – car parking, storage, garden etc.
• Easier access to the building and its entrances.
• Improved home layouts (currently do not reflect patterns of living).
• Balconies are small and of limited use.
• General lack of maintenance in the block and across the estate.

Project objectives

Top 10 priorities, developed through consultation and co-design workshops with residents:

• Kitchens
• Bathrooms
• Block entry system
• CCTV
• Communal Entrance
• Replace Lift
• Maximise hidden storage
• Redesign car park
• Communal décor
• Pest control

The council and funding from the Mustbe0 programme also required the retrofit to be net-zero, or as close to net-zero as possible.

Finance

The Treadgold House retrofit project is supported by the European Mustbe0 project, funded by the Interreg NEW Programme through the European Regional Development Fund.

An EU grant of £1.5 million was awarded to fund a net-zero retrofit of Treadgold House. This was extra funding that allowed the project to become an exemplar and demonstrator of what is possible across the UK and Europe, and what it would take to achieve as close to a net zero outcome as possible. This took the funding per flat from just over £70,000 to over £100,000 per flat.

United Living South Limited has been awarded the contract of £6.85million to design and build a whole house deep retrofit for the block. 

Procurement/contract management

Appointed an architect as project/contract manager. Extensive engagement and co-design has taken place with the residents of Treadgold House on the project since early 2018, including on developing the top priorities, feedback on initial design ideas, and voting on final design.

In November 2020, 87 per cent of households voted on whether they supported being a part of the Mustbe0 project, taking the refurbishment of the block to a net zero level, and 96 per cent voted to support this approach.

Timeline:

• Spring 2022 – appoint contractor to work on final design with residents.
• Autumn 2022 – work starts on site.
• Winter 2023 – planned completion.

The Retrofit

Prior to any measures being installed, energy performance measurements were carried out in each home in the block to ensure the retrofit would be carried out properly and would result in comfortable homes to live in.

Under the Energiesprong performance management framework the retrofit needs to result in properties that meet specific energy efficiency targets, such as space heating that requires less than 40kWh/m2/year. Essentially, this means the amount of energy required to heat each flat to a comfortable temperature is significantly reduced. The project also needs to be as close to net zero as possible, to align with the ambition of the Mustbe0 EU funding. The energy efficient improvements being delivered include:

• triple glazed windows.
• solar PV panels.
• non-combustible wall, floor, and roof insulation.
• mechanical ventilation with heat recovery.
• the removal of gas to be replaced with a series of communal Air Source Heat Pumps.
• as well as comprehensive internal refurbishment.

Benefits and Outcomes

The project is still ongoing and so final benefits and outcomes have not been realised yet. However, the retrofit measures to be installed have been chosen to achieve the following outcomes:

• Reduce energy demand of the building.
• Reduce energy bills for residents, benefiting from lower energy usage.
• Reduce the need for repairs and maintenance.
• Provide better air quality.
• Reduce noise from outside.
• Provide more comfortable homes for residents.

Challenges

Planning – The Air Source Heat Pumps for Treadgold will be sited on the roof. This has resulted in 2 key issues with the planning application. Firstly, there has been significant negotiations on how to enclose the heat pumps and how large that enclosure can be. This has added to the design work and caused delays in the planning application. Secondly there has been the need to do extensive acoustic testing.

Utilities – The Lancaster West Estate is upgrading the existing heat network to a low carbon heat network alongside refurbishing the whole estate to significantly improve the energy performance of all homes. Initial discussions with the District Network Operator (DNO) indicated that Treadgold House wouldn’t need a new substation. Further work with the DNO has established Treadgold will need a substation upgrade – however this has become clear late into the planning process.

Budgets – delivering an ambitious whole block approach during a time of such high inflation and supply chain pressures has been challenging.

Insulation – fitted to the walls, roof or floor of the building - reduces heat loss from the building. It can also help limit overheating in summer.

Older blocks of flats are less likely to have insulation than houses of the same age. But insulating blocks of flats is essential for people who live in flats to have warm, comfortable, low carbon homes.

The benefits of insulating the building

• Insulation reduces the amount of energy needed to heat the buildings: that means lower energy bills, and/or a more comfortable home (because residents can afford to heat the home to a higher temperature).
• Installing insulation can also cut down on draughts, again improving comfort.
• Correctly designed and fitted insulation – which also takes appropriate ventilation into account – can also reduce damp and mould problems.
• Because insulation reduces the amount of energy needed for heating, it is an important measure to reduce the carbon emissions from the building: it’s a vital step to making the block of flats net zero ready.
• Insulation is also a key step in making the building ready for other energy and carbon saving improvements. For example, heat pumps can work most effectively in well-insulated buildings. Insulation is the key step in taking a fabric first approach.

Considerations and challenges

Poorly designed and installed insulation can cause major problems: Its vital to work with an expert, such as a PAS2035 accredited Retrofit Assessor and Coordinator, to ensure plans for insulation will not cause problems for the building – even if it seems like a straightforward upgrade.

Any structural issues or building problems should be carefully assessed and if necessary dealt with before installing insulation improvements, for example, damp or rot in walls or joists.

From a technical point of view, it can be better to aim to work at a whole building level, rather than installing insulation in individual flats. So called “thermal bridges” can occur when there are gaps in the insulation. A thermal bridge is an area of a building that has a higher rate of heat loss than the surrounding parts: unless thermal bridges are carefully considered at the planning stage they can reduce the effectiveness of the insulation and lead to damp and mould problems.

For the same reason it’s a good idea to undertake different insulation projects (for floor, walls or roof) at the same time. That way the designer can plan for joins in the insulation.

Think about ventilation at the same time as improving insulation because the insulation will make the building more airtight and change the balance between warm and cold spaces and materials in the building. Ventilation needs to be considered in all aspects of the insulation project: for example it’s important to ensure that the roof and underfloor spaces remain ventilated, as well as living spaces.

Bear in mind planning rules which apply particularly when insulation will affect the external appearance of the building. See section 3.2.

As with all aspects of retrofit, fire safety is a key consideration: ensure that any insulation works, and the materials being used, are compliant with all relevant fire safety standards and guidance. Before proceeding it is vital to inform and seek the agreement and consent of all stakeholders of the plans for insulation, take all necessary advice on this point, and seek agreement from all parties who need to give consent – landlord, leaseholders, managing agents, mortgage lenders etc.

Types of insulation 

The type of insulation that’s right for a property will depend on the construction of the building and many other factors, such as its location and exposure to rain. It’s vital to work with an expert to decide what type of insulation is right for the building, and how it should be installed, even if it seems straightforward. 

Cavity wall insulation

Many twentieth century blocks of flats are of cavity wall construction: cavity wall insulation is a long-established technology, whereby insulation is blown into the cavity.

For low rise houses and smaller blocks of flats, cavity wall insulation can often be undertaken quickly and easily. For blocks over three stories, the process can be more complex involving scaffolding and with additional safety requirements.

External and internal wall insulation

Older buildings (particularly those constructed before around 1920) usually have walls of solid brick construction. For these buildings, as well as for other buildings not of cavity wall construction, it can be possible to fit insulation to the outside or inside of the walls.

Internal wall insulation can be fitted within individual flats. This offers the benefit of being something that leaseholders (with landlord consent) can undertake inside their own property, without needing to co-ordinate with other flat owners. However, because there are more breaks in the insulation when its fitted flat by flat, internal wall insulation can pose more challenges for thermal bridging.

External wall insulation can be fitted to the outside of the property: as such it is a measure that will usually need to be installed by the landlord.

It is possible to use both internal and external insulation on different walls in the same building, which may be desirable, for example, to preserve the appearance of the façade of the building.

Floor insulation

For suspended timber floors, insulation can be fitted between joists, under the floorboards. It may be fitted from beneath, or by lifting the floorboards. For concrete floors, insulation is usually fitted as insulated boards over the concrete floor.

Roof insulation

Loft insulation can be rolled out between joists as a quilt or blown as a loose fill into harder to access parts of the roof space. Most buildings now have at least some loft insulation but this may need topping up: the typical recommended level of insulation (by the Energy Saving Trust) is now 270mm. Where there is a room in the roof, insulation can be installed at rafter-level. For flat roofs, insulation can be fitted as insulated boards on top of the current roof structure, beneath a waterproof membrane.

Making the most of an insulated flat

• A well-insulated flat should be warmer and more comfortable. It may be necessary to adjust heating controls to avoid overheating.
• Pay close attention to ventilation, and – as part of the plans for the insulation - seek advice on improving ventilation.

For more information and advice

For support and advice on saving energy, visit Energy Advice London or telephone free on 0808 196 8260 to speak with an advisor.

Energy Advice London's service is are open to all, Monday to Friday from 9am to 5pm (excluding bank holidays).

Centre for Sustainable Energy have resources, advice and information on their website.

It’s vital to consider ventilation when thinking about energy efficiency upgrades such as insulation or double glazing because these upgrades will make the building more airtight and change the balance between warm and cold spaces and materials in the building – unless this is planned for, condensation and damp can be the result.

This section provides information about ventilation systems used in modern homes, to help think about the potential for improved systems in the flats in the building.

As part of retrofit planning, discuss the potential for ventilation upgrades with the expert involved in planning your project.

Information in this section is adapted from the Home User Guide Template and Existing Home Ventilation Guide published by the UK Government. Contains public sector information licensed under the Open Government Licence v3.0.

Why is ventilation needed in homes?

Ventilation in homes is provided for three reasons. The first is to supply fresh air for the occupants. The second is to help to ensure good indoor air quality, which needs removal of enough moisture, odours, and other indoor pollutants. The third purpose is to help to maintain good thermal comfort; ventilation air flows help heat to mix from different sources, so it circulates throughout your home, especially from the central heating system during cold periods. The different parts of the ventilation system work together to allow fresh air to through throughout your home.

Poor levels of ventilation along with excess moisture in the indoor air can contribute to mould growth, so it is important to use the ventilation provided to keep homes ‘fresh’ and to remove moisture at source, particularly from shower rooms, bathrooms and kitchens.

Types of ventilation system

The most modern homes built to a high energy efficient standards will be very airtight to minimise heat loss, as such they use mechanical rather than natural ventilation. Retrofitting a mechanical ventilation system may be required when buildings are made much more energy efficient, but can pose challenges with new ducting and cabling needed in both the flat and through communal areas.

Natural ventilation

Natural ventilation is provided using boost only extract fans in shower rooms, bathrooms and kitchens, with trickle vents in all window frames, and openable windows. Trickle vents are small openings fitted within all window frames in the home, which allow background ventilation air flows to help to maintain good indoor air quality. Local extract fans in shower rooms, bathrooms and kitchens (in a non-recirculating cooker hood) provide ventilation air flows to remove high amounts of moisture, odours and other indoor pollutants using fans powered by electricity. These will often come on with the light switch and stay on for a timed period after the light has been turned off, and are also humidity controlled.

Mechanical extract ventilation

Ventilation is provided using continuous mechanical extract ventilation from shower rooms, bathrooms and kitchens, with trickle vents in most window frames, and openable windows (see natural ventilation above).

Continuous mechanical extract ventilation from shower rooms, bathrooms and kitchen provides background ventilation air flows to remove moisture, odours, and other indoor pollutants from the home, with fresh air supplied through trickle vents. This type of system is intended to run continuously using fans powered by electricity and should only be switched off if they are being worked on by a professional installer.

Each fan can also be switched to boost mode to temporarily increase the ventilation air flows when needed. Opening windows allow for additional ventilation when needed. To allow air to circulate around the home, doors may have gaps underneath them.

Mechanical Ventilation with Heat Recovery

Ventilation is provided using mechanical ventilation with heat recovery and openable windows. Mechanical ventilation with heat recovery (MVHR) systems extract air from shower rooms, bathrooms and kitchen, supply air to the living room and bedrooms, and so provide continuous background ventilation air flows to remove moisture, odours, and other indoor pollutants from the home. This type of system is intended to run continuously at all times using fans powered by electricity and should only be switched off if it is being worked on by a professional installer; it can also be boosted to increase the ventilation air flows when needed.

Heat recovery means that the warm air exhausted from rooms in the home is sent through a heat exchanger (in the MVHR unit) which transfers most of its warmth into the fresh air coming into the home. This means residents can have plentiful fresh air ventilation while losing little heat. The heating system will therefore not have to work to replace the heat normally lost to ventilation which should make the home less costly to run. (With certain models, it may be possible to switch the MVHR unit to a 'summer bypass mode’, so that incoming fresh air does not pass through the heat exchanger and so is not pre-warmed).

Opening windows allows for additional ventilation when needed. To allow air to circulate around the home doors may have gaps underneath them.

How to use ventilation?

In order to ensure the ventilation in the building works as well as possible, you should:

• Always leave trickle vents open and unblocked, even in winter. You will use a little more energy to heat your home, but have fresh air to prevent illnesses.
• Where possible, leave doors between rooms open to ensure cross-ventilation. This will further improve the amount of fresh air drawn into the building.
• Regularly clean any extractor fans in bathrooms and kitchens.
• Check the manufacturer’s instructions for any whole house mechanical ventilation system. It’s vital to keep the filters replaced in line with those instructions, usually this would be annually.
• MVHR and continuous mechanical extract ventilation are designed to run continuously: its vital that you don’t turn them off. You are unlikely to save energy as a result and any resulting damp and mould could add significantly to the costs.
• Where flats are sub-let its vital that residents are advised on how to use the ventilation system.

For more information and advice

Learn more about ventilation from the Centre for Sustainable Energy here. Specific information and advice on MVHR can be found at the same site – download a PDF guide here.

Knowing how energy is used in the communal areas of the building and in individual flats is the first step to understanding how the building can be more efficient.

Energy data is valuable both at individual flat levels and – particularly for planning whole building retrofit - at building level. Building level data may come from energy meters in communal areas. Larger or more modern buildings may have building energy monitoring systems that provide additional data on the amount of energy being used by particular systems such as lighting.

Gathering energy data will be easier where properties have smart meters: smart meters are being rolled out across UK buildings; in a block of flats energy use in both individual flats and communal areas may be metered through smart meters.

The benefits of checking how you are using energy

By checking when most energy is being used, residents can benefit from immediate savings to energy bills and reductions in carbon emissions by changing the way they use energy.

Residents may want to share energy bill information. Comparing energy bills from different flats with different features (e.g., heating systems) and situated in different parts of the building may help you to understand opportunities to reduce energy use across the building.

Challenges and Considerations

Energy data is sensitive, personal data, so its important that any sharing of energy bills data is carefully managed, has full written consent of the residents involved and is undertaken in a way that is compliant with Data Protection Regulations.

Every household is different, and people might have very different energy needs. For example, people who are elderly or disabled may need to keep their home warmer and so will tend to use much more energy for heating. So it may be that the amount of energy used has little connection to the energy and carbon related performance of the flat.

For people living in flats and buildings connected to communal or district heating systems, it may be necessary to talk to the manager of the system to request access to data on your heating energy use.

Smart meters for individual flats

Information in this section is adapted from Smart meters: a guide for households - GOV.UK (www.gov.uk). Contains public sector information licensed under the Open Government Licence v3.0.

Unlike traditional meters, which simply register a running total of energy used, smart gas and electricity meters can record half-hourly price and consumption data and provide automatic meter readings to the energy supplier.

Most homes have two meters, one for gas and one for electricity – both will be replaced with smart meters. Home-owners are also offered an In-Home Display (sometimes referred to as an IHD), an easy-to-use handheld device that sits within the home. This shows residents the cost and amount of energy they are using, updating every 30 minutes for gas and in near real-time for electricity.

The installation will also include a communications hub, which allows the smart meters and IHD to communicate with each other, and links your smart metering system to the secure national smart meter network.

The government identifies that smart meters bring benefits in terms of:

• Residents only being charged for the energy they use rather than receiving estimated bills.
• The In-Home Display (IHD) shows households their energy use in near-real time, expressed in pounds and pence.
• Prepayment customers see additional benefits, as smart meters allow: customers to top-up remotely without leaving home; customers to see credit balances on an easy-to-access In-Home Display, so they do not unknowingly run out of credit; customers can top-up automatically.
• Consumers may be able to opt for electric vehicles, heating systems and smart appliances, such as washing machines and dishwashers, that can connect to the smart metering system to access pricing data. Activity can be programmed to automatically take advantage of cheaper rates, reduce the impact on our energy grid and save consumers money.

Smart meters in communal areas

For smart meters measuring energy use in communal areas, customers will not normally receive an IHD, but the smart meter should enable the supplier to provide additional, detailed information on patterns of energy use.

If energy use in communal areas is managed by a business and there is not currently a smart meter installed, Smart Energy GB advise that the business can request one through its energy supplier or broker, or through their website.

For more information and advice

Households can request a smart meter from their energy supplier.

For more technical information and detailed consumer advice about smart meters, visit Citizens Advice.

To find out more about using an IHD and how to read smart meter, data visit this page from Smart Energy GB.

For blocks of flats with grounds, a ground source heat pump (GSHP) is a way of providing heating and hot water to flats in the block.

What is a ground source heat pump?

A ground source heat pump uses electricity to extract ambient heat from the ground and deliver it as usable heat inside the building. Compared to air source heat pumps (ASHPs) used for individual homes, GSHPs are usually larger systems with a higher heat output. That means that – for blocks of flats – they are normally deployed as communal systems with the heat supplied to multiple flats or units in the building. Each flat then has a heat interface unit to connect the individual flat’s heating and hot water system to the communal heat supply.

Other things being equal a GSHP may be more efficient (deliver more heat per unit of electricity going in) than an ASHP: that’s because the ground maintains a steady, warm temperature year round. However, because of the need for extensive underground pipework, installing a GSHP may be a much larger scale project than installing an ASHP.

Benefits of GSHPs

Very high efficiency heating: because it uses the ambient heat in the ground, a well-functioning heat pump is able to provide heat from electricity at well over 100% efficiency.

Running costs: for some homes, a GSHP can deliver lower cost heat than the installed heating system. Future government changes to taxes and charges on energy may make heat pumps more cost effective against gas.

Flexibility (and running costs): A heat pump with a thermal hot water store can use electricity to heat water at times when electricity is cheapest, enabling additional bill savings.

Future proofing: with its net zero target, the government is clear that buildings need to move away from gas and oil heating. Installing a GSHP could ensure that the building is ready for any future regulations or standards as the UK moves away from high carbon heating.

Safety standards: Switching away from gas in a building can make it easier to comply with some safety standards (for example, private landlords have to have an annual safety check of a gas boiler).

Currently, a GSHP could be a good solution for buildings with existing communal heating system heated by oil or gas – particularly where this is old and needs replacement/updating.

Considerations and challenges

Switching a block currently heated by individual gas boilers or individual direct electric heating units to a communal heating system is likely to be challenging unless all leaseholders and the landlord are on board with the plan, and willing to switch over the systems in their building and in their individual flats. A shared ground loop system may offer more flexibility.

It's important to take a fabric first approach: if the building needs additional insulation it’s a good idea to get that installed first, before proceeding with a heat pump installation. Work with a retrofit assessor or other expert to make a whole building retrofit plan before proceeding with the installation.

Installing a GSHP

The key requirement for installing a GSHP is sufficient grounds around the block to allow the installation of the ground loop pipework that extracts the heat from the ground. The ground loop pipework for a GSHP can be laid across an area of land as a horizontal loop or in a borehole drilled vertically. In an urban setting, due to space constraints, a borehole is likely to be the viable option.

How a heat pump works

Heat pumps are a long-established technology. A GSHP consists of the array of pipework which absorbs the heat from the ground and an evaporator and condenser which, together, upgrade the heat so it can be delivered as usable heat for residents.

Option: Shared Ground Loop system

In a shared ground loop system, the ground loop absorbs heat from the ground but, rather than a single large heat pump serving the building, each flat or unit in the building has its own heat pump connected to a distribution system circulating heat from the ground loop.

This can offer benefits in terms of:

• More control for householders – each flat will be responsible for their own heat pump and electricity use for heating.
• Balance between building level and flat-level action – because more of the system is installed at the individual flat level, leaseholders may be more able and ready to invest.

Option: Communal air source heat pumps

There is an opportunity for communal air source heat pump systems. Where feasible, a large air source heat pump can be installed on a roof or external area. The communal aspects of the system – supplying heat to the individual flats – would work in the same way as described here for a ground source heat pump.

Presently, this is less common than GSHPs but it may be an option to consider if the building has a suitable roof. For the time being, air source heat pumps may be more likely to be fitted for each individual flat. See our case study of Treadgold House which is using this solution. See also information about individual air source heat pumps.

Insulation and heat emitters

Buildings with a good level of insulation are well-suited for this technology. The use of larger heat emitters in a property may be useful to ensure the most effective operation: that can mean switching to larger radiators in some homes. Underfloor heating also works well with a heat pump.

For more information and advice

For support and advice on saving energy and money, visit Energy Advice London or telephone free on 0808 196 8260 to speak with an advisor.

Energy Advice London's service is are open to all, Monday to Friday from 9am to 5pm (excluding bank holidays).

For more technical information, see the Heat Pump Association's website. 

To find an installer, or learn about how installers are certified for quality, visit the Microgeneration Certification Scheme (MCS) website.

To read about consumer protection standards for renewable energy installations, visit the Renewable Energy Consumer Code.

Air source heat pumps are a highly efficient type of heating system. Using electricity, they are able to extract ambient heat from the air – even in the coldest days of winter – and deliver it as warmth inside the home for hot water and/or space heating.

There are different types of air source heat pumps on the market including:

• Air to water heat pumps – that provide heat for a “wet” central heating system for heating hot water and radiators (similar to a standard gas boiler based system).
• Air to air heat pumps – that provide space heating in the form of hot air inside the building. These are widely used in the commercial sector and are often referred to as “air conditioning.” They can often also provide cooling in summer.
• Hot water only heat pumps – these provide heat for a hot water tank only, rather than providing space heating.

Communal scale air-to-air heat pumps can be used to provide heat across a building – see discussion under ground source heat pumps.

Benefits of an Air Source heat pump

High efficiency heating: because it uses electricity to extract ambient heat from the air, a well running heat pump is able to deliver more than one unit of heat for each unit of electricity used. That’s a higher level of efficiency than can be achieved from direct electric heating or from a gas boiler.

Running costs: Depending on the home, a well-running heat pump fitted right for the flat may be able to deliver lower running costs than the current heating system, particularly if using direct electric heating. The government has indicated that it is considering if and how taxes and levies on gas and electricity bills could be adjusted to make heat pumps a more cost-effective choice in future for home owners using gas boilers. Customers who switch away from gas completely will no longer pay a gas connection standing charge.

Flexibility (and running costs): A heat pump with a thermal hot water store can use electricity to run at times to heat water when electricity is cheapest, enabling additional bill savings.

Future proofing: with its Net Zero target, the government is clear that buildings need to move away from gas and oil heating. Installing an ASHP will help ensure that the building is ready for any future regulations or standards as the UK moves away from high carbon heating.

Considerations and challenges

Heat pump based heating systems may cost more to buy than direct electric heating: where flats are small and well insulated, the additional upfront costs of the heat pump may not offset lower running costs, when compared to direct electric heating. It may be worth considering space heating and hot water separately: some flats have space heating using direct electric heating, with hot water provided from a hot water only heat pump.

Fitting several external ASHP units to the building could be a visually unattractive choice – though there may be ways to hide the external units. Landlords and planning authorities may be reluctant to give consent where many units are planned. The extractor units also make some noise (though this depends on the model and how they are used) and this will need to be considered.

If more than one flat owner may be likely to want to install a heat pump – and note that government policy is promoting heat pump uptake – it may be a good idea to consider a building-wide solution, which will require only one external heat pump unit, or research options for ASHPs that work via air ducts vented to the outside rather than requiring a separate external unit. See our guidance on communal ground source heat pump and on shared ground loop system.

Buildings with a good level of insulation are well-suited for this technology. With some heat pumps the use of larger heat emitters in a property may be beneficial. That can mean switching to larger radiators in some homes. Underfloor heating also works well with a heat pump.

How does an air source heat pump work?

The diagram below shows how an air to water heat pump works. A fan draws in the air. The heat pump evaporator extracts the heat from the air and a condenser delivers it as warmth inside the building. In most heat pump systems, the fan and evaporator unit sits outside the building while the condenser sits inside the building.

However, some systems suitable for some flats – particularly hot water only heat pumps - can work without an outside unit, instead drawing in the air through ductwork from the outside.

Considerations for leaseholders considering installing a heat pump

• The installation will often cut across the communal areas of the block and the inside of the flat which belongs to the individual leaseholders. All stakeholders – landlord, managing agent, leaseholder and resident – need to understand what is being planned and how the installation will happen, and to have provided the necessary consent.
• If a leaseholder intends to access a grant from the Boiler Upgrade Scheme, they will need to use an installer who is accredited by the Microgeneration Certification Scheme (MCS). Search for an MCS certified installer in the area here.
• Make sure to double check planning rules – planning permission is usually required if more than one external ASHP unit is being installed on a block of flats and there are other rules that it is important to consider. See section 3.2 for more on planning.

Living with an air source heat pump

Heat pump-based heating requires some changes in the way households manage their heating system. For example, they work best when providing steady, low temperature heat so – unlike a gas boiler – it can make sense to leave a heat pump running through the day, turning it down when less heat is required, rather than turning it on and off when heat is needed.

Where flats are sub-let it’s vital that leaseholders provide clear guidance for their tenants on how to use the new system.

For more information and advice

For more technical information see the website of the Heat Pump Association.

To find an installer, or learn about how installers are certified for quality, visit the Microgeneration Certification Scheme (MCS) website.

To read about consumer protection standards for renewable energy installations, visit the Renewable Energy Consumer Code website.

What is direct electric heating?

Direct electric heating refers to any sort of electric heating, other than heat pump-based heating. Types of electric heating used in flats include - for space heating - storage heaters, panel heaters or electric underfloor heating. Direct electric water heating can include tanks with immersion heaters or point of use (at the tap or shower) electric heating: this is often used to heat hot water in flats where communal or district heating provides space heating. Some homes have electric boilers which, like a gas boiler, can heat water for both radiators and hot water.

In this section we’re discussing direct electric as a primary (main) heating system: secondary electric heating such as fan heaters are used in many homes to supplement the main heating system.

Though direct electric heating has been around for a long time, it’s likely to be an important part of the net zero future for blocks of flats.

Direct electric heating: Summary of the benefits

• Often lower purchase costs for the system, as compared to gas or heat-pump based systems.
• Can often be fitted within flats without wider disruption/need for installation in common parts of the building.
• Can be easy to use, understand and control for residents and maintain for leaseholders.
• Works well with solar PV panels when these are fitted on the building.
• Increasingly a low carbon choice as grid electricity in the UK more and more comes from renewable energy.
• Some systems can use energy flexibly at different times of day, when it is cheaper– helping to reduce bills.

Direct electric heating: Summary of challenges and considerations

• Less efficient heating than a well-functioning heat pump-based heating. Gas is generally cheaper per unit of energy than electricity.
• Insulation is key: often direct electric heating is a good choice for smaller, well insulated flats.
• When considering electric heating it is useful to compare the upfront costs of the system against the running costs over 10 or 15 years. A retrofit assessor or other expert will be able to help with this assessment and flat owners might want to work together to look at direct electric heating against other communal or individual heating options for the building.

Direct electric heating: an important part of the future heating systems for flats

Direct electric heating is likely to be a big part of the future of heating for blocks of flats:

• Electricity in the UK is increasingly low carbon, so direct electric heating is compatible with the UK’s trajectory to Net Zero.
• As flats become increasingly well insulated (both because newly built flats increasingly have to meet stringent insulation standards and as older flats are refurbished) they have lower energy demand which means that direct electric heating can be a good, straightforward choice.

• A key part of the government’s plan for the future of heating in the UK is to use energy flexibly: enabling householders to use electricity at times when it is most cheaply available on the grid. Storage heaters are a long established - but increasingly sophisticated - technology that are designed to maximise this potential.
• Electric heating can be used alongside solar photovoltaic panels on the roof of the building, which can generate free electricity for use in the heating system. Homes or buildings with solar panels might increasingly have batteries to store electricity for when it is needed for heating.

Types of direct electric heating

Storage heaters

Storage heaters have been used in UK flats for decades and are designed to minimise the running costs of electric heating. Electricity is used at times when it is cheaply available (usually overnight) to heat bricks inside the heater. The heat is then released when it is needed by the resident. To benefit from a storage heater, residents need to be signed up to a dual or flexible energy tariff such as Economy 7 (and have a dedicated meter to enable this) which offers lower cost electricity at certain times of the day.

Older storage heaters usually do not perform as well as the advanced models today. The latest storage heaters are designed to deliver high heat retention (reducing the risk of them running out of stored heat during the day). They can also be fan assisted. They can have smart controls: they will increasingly be digitally networked to other systems so that, for example, they can store energy when a solar PV system is generating electricity.

Panel heaters

Panel heaters or electric radiators are fixed to the wall and convert electricity directly to heat which is released into the room. Panel heaters increasingly have smart controls and thermostats to allow them to be used only when heat is needed.

Electric boilers

These systems use electricity to power a boiler for a central heating system. For hot water, they can be used with Economy 7 or another flexible energy tariff: programmed to heat hot water at times when electricity is cheaply available.

For more information and advice

Learn more about electric heating options from the Energy Saving Trust here.

The Centre for Sustainable Energy also has information and advice relating to Economy tariffs required for some electric heating systems here.

There are two types of solar panels available: solar photovoltaic (PV) panels which generate electricity. Solar thermal panels use the energy of the sun to heat water. In the UK, solar PV is the much more widely used technology and is the focus of this section.

For blocks of flats, depending on agreements between leaseholders, landlord and other parties, installing solar PV panels on the roof may generate electricity for the use of residents and/or for communal areas. Solar panels can also provide a source of revenue as excess generation (ie the electricity not used in the building) is exported to the national grid.

The benefits of solar PV panels

Installing solar PV may bring some or all of these benefits:

• Lower energy bills or service charges – either because solar energy is used to provide power for communal areas or is used by residents.
• Revenue from exporting excess electricity generation to the national grid.
• A clean energy source – solar panels generate zero carbon energy; a key contribution to enabling the building to meet net zero.
• Can be combined with modern clean electric technologies – heat pumps; the latest direct electric heating systems; electric vehicle charging. Batteries are increasingly viable technology as a way to store generated electricity from solar photovoltaic panels.
• Solar PV generally requires limited maintenance when in-use.

Challenges and considerations around installing solar PV panels

• Think about taking a fabric-first approach. Installing renewable energy systems like solar PV can bring many benefits, but a well insulated building will often be able to make the best use of the clean electricity generated by solar PV panels.
• Bear in mind planning rules (see our Planning Section): solar panels can often be installed on blocks under permitted development rights, but it depends on the building and the installation.
• Work with a retrofit assessor or other expert to assess the suitability of the building for solar PV and to consider how solar PV could work alongside other retrofit measures.

Pitched Roof

Solar panels installed on a pitched roof (source: Repowering London)

Flat roof

Solar panels installed on a flat roof (source: Repowering London)

Installation considerations

• The solar PV panels need to be oriented broadly towards the sun, so roof orientation is a consideration, as is the pitch of the roof, if you are installing on a pitched roof. Trees or other buildings around your block may shade your roof which could make the panels less effective at generating electricity.
• Components of the system will need to be installed in the building. An inverter will need to be installed: this turns the electricity generated by the panels into electricity that can be used in the building or exported to the grid. Cabling through the building will also be required.
• Installations can be made on flat roofs or pitched roofs. A flat roof installation can be more straightforward. In either case, roof condition is an important consideration: the installer will confirm that the roof is in good condition and able to support the panels. If upgrading the roof, this can be a good opportunity to install panels.
• Different types of solar panels are available. For example, solar tiles are now available that can be installed flush with the other tiles on the roof.
• Scaffolding will usually be required to install the panels. It’s worth considering if scaffolding could be used to install other retrofit measures.
• Assessing for and planning for solar PV will usually involve multiple stages: there are online tools to provide an initial assessment, site visits and then detailed structural assessments will be needed to plan for the installation process.

Making the most of solar panels

Depending on who owns the solar panels and who pays the electricity bill, it can be better to use the electricity generated by the solar panels in the building than export it to the National Grid. That’s because the free electricity from the panels – when used in the building – means flats and/or communal spaces aren’t using electricity from the grid that costs (in January 2023) around 34p per unit at standard rate. Payments for exporting the electricity to the grid are usually lower – the government’s Smart Export Guarantee programme guarantees only that energy companies will pay more than zero pence per unit for electricity exported from solar PV panels on homes.

Where energy from solar PV panels is provided for residents, maximising the benefits of solar panels will mean aligning electricity consumption with the generation from the solar panels. For example, it can make sense to run a washing machine in the middle of the day when free electricity is available from the PV system.

For more information and advice

To find an installer, or learn about how installers are certified for quality, visit the Microgeneration Certification Scheme (MCS) website.

To read about consumer protection standards for renewable energy installations, visit the Renewable Energy Consumer Code website.

The Centre for Sustainable Energy also has helpful advice pages on solar PV and solar thermal.

Who is this information for?

Landlords, leaseholders and managing agents interested in building-wide retrofit improvements to their block of flats. 

What does this section cover?

This section provides a simple template to consider the benefits of energy and carbon saving retrofits in a block of flats.

Who is this section for?

Landlords, building managers, leaseholders with management responsibilities of private sector blocks of flats, retrofit professionals helping plan a retrofit project for blocks of flats. 

What this section covers 

Understanding the energy performance of individual flats and the whole building will help to identify the best upgrades to make as part of a retrofit project. 

This section presents guidance on the data to gather on the building to help plan for low-carbon upgrades. 

Ensure consent is in place from the landlord, building manager and any other party who needs to agree to this exercise, before proceeding to gather this information. It is vital that permission to collect and hold the information complies with Data Protection Rules. 

This section is divided into two sections. Firstly, there is a set of tables to help think about the data that it would be useful to collect. This is a first indication – any information will be useful. 

Information on individual flats can be found in Energy Performance Certificates. These have to be provided and lodged on a national database when a home is rented out or sold. We also present information on understanding and analysing EPCs. 

Collecting data – introduction

The first step should be to go through the points listed above with the landlord, managing agent, or the leaseholders responsible for building maintenance and management. They will want to refer to: 

• Plans of the building and records of maintenance and upgrade works. 

• Upkeep and maintenance agreements with third parties. 

• Data on the energy used in the whole building. Try to look back over historic bills and see if the amount of energy used in the communal areas of the building has changed and to understand why. See if the managing agent has information on the energy used by specific systems, such as communal lighting and lifts. 

Most importantly, ask them for their views and insights. What are the particular problem areas of the building? Why? Are there any parts of the buildings where energy/carbon performance could be improved – are they aware of any uninsulated areas? What has been considered in the past and not taken forward? Why? 

What data to collect – summary tables

*See section 2 below

Communal and district heating systems

Communal and district heating systems

Rather than individual heating units in each flat, the building may have a single centralised, communal heating system for the whole building, or it may be connected to a district heating system providing heat for multiple buildings.

Communal heating

Most energy use in residential buildings goes on heating. Understanding the way heating is fuelled/powered and provided through the communal system should be a top priority for initial data gathering. Seek a meeting with the managing agent and any other companies involved. Focus on understanding four areas:

• The boiler or other heat source.
• The distribution system through the building.
• The controls for heating in the individual flats.
• The ownership, management and maintenance of the heating system.

District heating system

Unless the multiple buildings served by the heating system are all on one estate, there may be little action that can be taken at the individual building level to influence the carbon emissions from the heat generation. However, the building manager may have views on how the heat distribution system in the buildings could be improved, fitted with new heating controls, etc.

Energy Performance Certificates

The first step is to collect EPCs for the building. An EPC shows the energy performance of a home or non-domestic business premises and recommends measures that could improve this.

The EPC for an individual property can be found by searching for the postcode on the EPC register.

The headline rating on an EPC is an A (good) to G (bad) rating for the overall energy performance. This is based on a 1-100 score.

Because EPCs provide information for individual flat owners, they don’t recommend building level upgrades that flat owners cannot do by themselves. So, an EPC won’t provide an estimate of the building- wide potential for insulation, which could be a good building-wide measure to reduce heat loss. It won’t recommend communal (building- wide) heating system options. An EPC won’t recommend solar panels that could go on the roof of a block of flats.

Considerations when looking at an EPC

Firstly, check the dates on the certificates. EPCs have been issued for homes and other buildings since 2008. If the EPC is old, identify if upgrades to insulation, windows and heating systems have been made since the date of the certificate.

Check the certificates against other information about the flat and building. Does the EPC make sense to you in terms of the information in it about the type of flat, its construction, size, etc.?

Try to understand why different EPC ratings have been given to different flats. The rating will be affected by the heating system, the glazing and any insulation that’s been fitted inside the flat or on the external walls. The EPC rating will also be affected by how big the flat is and where it is positioned in the building: for example, top floor flats lose heat more easily than middle floor flats and so will typically have a lower rating compared to a mid-floor flat of the same size and shape and level of insulation.

“C” is a critical dividing line for government funding support for energy-efficiency upgrades. Try to understand why any flat rated below C has a lower rating and what are the upgrades that will bring it above this line. Look not just at the letter rating, but at the numerical score that underpins it: is a D rated flat just below the C boundary of a score of 69, or is it closer to the bottom of the D band at 55?

The next step is to review the recommendations on the certificate. What upgrades does the EPC suggest to improve the energy-efficiency of the flat? (Remember where the EPCs are old, the upgrades might already have been made). EPCs for flats certainly won’t tell you about all possible upgrades. In particular they won’t usually recommend upgrades that need to be made at the building level.

Non-domestic EPC assessments

If the building has been sold as a whole block since 2008 and/or if there is a commercial premises in the block, there may be non-domestic EPCs available to cover the communal areas of the building or the commercial premises. Non-domestic EPCs are on the EPC register here: Find an energy certificate – GOV.UK​