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Preparing a retrofit project

3. Developing retrofit interventions


Developing a plan for the retrofit interventions you will deploy in the project is one of the most complex and most technical tasks in the preparation phase.

It starts with reviewing your housing stock, its type and condition, and leads to a plan for what you want to do with the stock to improve its energy efficiency and its performance.

The goal is to create a specific project targeting a named set of buildings, with a practical series of retrofit measures that will deliver outcomes that meet your strategic objectives, including the needs of any external funders.


    Key steps to take

    We have broken the task down into five main steps:

    1. Stock analysis – This step is about understanding your housing stock, the type and construction of buildings, their condition and their current levels of energy efficiency so you can create a clear baseline for your project.

    2. Deciding target outcomes – Given the stock and its condition, and the objectives of the organisation, consortium partners and funders, what are our goals? What would be a success for the retrofit project?

    3. Identifying target properties – Given the stock and our target outcomes, which selection of buildings will we include in the retrofit project? This might be a geographic cluster, a particular building type or properties with specific EPC ratings.

    4. Preliminary design – Which combination of energy efficiency and other measures should we apply to our selected properties? How do we create a whole-building plan that is technically deliverable, economically viable, and delivers the target outcomes?

    5. Risk assessment – What could go wrong with our chosen approach? We may fail to deliver the projected energy savings. We may damage the building fabric or have negative effects on residents health and well-being. How can we mitigate these risks in the design or implementation of the project?

    The sequence of the steps is not completely linear. It is a more fluid conversation in which each activity influences the others. For example, an initial risk assessment may force you to reconsider your design. Developing a practical design may suggest selecting a different set of properties for the project. The target outcomes you chose may be too ambitious, and you might want to go back to the stock analysis for new inspiration.

    Stock analysis

    Stock analysis requires a combination of two activities: gathering relevant data and then analysing it. The quality and accuracy of your analysis will depend on the quality of the data that you use.

    In this guidance, we will explore what “good data” looks like, how it can be gathered, how to think about data analysis and considerations for selecting home energy analytic software.

    Why it matters

    A good understanding of your housing stock is important to:

    • Identify properties for retrofit

    • Give you a better understanding of the technical requirements and retrofit opportunities for each property

    • Model retrofit energy efficiency investments in each property to reach set targets (for example, EPC C or net zero).

    • Provide estimated costs for retrofit works

    Good stock data is essential to planning and delivering a retrofit program so make sure you have reliable stock data should be one of the first things you do.

    Knowing about your homes and the people who live in them can help you to prioritise homes for improvements, aggregate similar homes for retrofit programs and deliver energy advice services that meet the needs of your residents. Ensuring that your data is fit-for-purpose helps give you confidence in the decisions that you make and provides baseline evidence for measuring the results of the work that you do.

    This guidance focuses on data for designing and planning your retrofit project. It also touches on data for monitoring and evaluation , which is covered in more depth on this Knowledge Hub. If you are applying to the Social Housing Decarbonisation Fund (SHDF), you should read the Competition Guidance which will help you think about data that you will need through the lifetime of your retrofit project.

    Key steps to take

    1. Know what data you need – do you have enough data about your housing stock to accurately describe its type, condition and energy consumption? Types of data might include:

      • Stock condition and EPC data

      • Resident feedback on the property, eg through complaints or turnover rates

      • Asset renewals and repair records

      • Complaints and HHSRS requirements

      • Planned maintenance opportunities and budgets

      • Demographics and income data of residents

    2. Understand what data you already have within the organisation, who is responsible for managing it and any limits to its use – such as the age of the data, or any confidential information.

    3. Find data held by others. Identify what external data sources are available that could supplement what you hold internally.

    4. Figure out what you don’t know. Identify any data gaps and make a plan to address these. For example, you may have a lot of data about certain estates or housing types, but not others.

    5. Organise your data. Ideally, your data should be in a central database and a standard format, but we recognise that this isn’t always the case. Read the guidance below for more on organising data.

    6. Assess the quality of your data. Once you have gathered data, you should assess it by asking three questions. How complete is it? How up-to-date is it? How reliable is it? Is the data cloned from similar building types or has it been drawn from actual visits to the home?

    7. Get your data ready. Prepare your data for analysis through a structured approach to data cleaning; more on this is in the guidance below.

    Success factors

    Persist. It can take time to corral all of the data you need from different parts of your organisation. If your project is aligned with corporate goals and can be shown to help different teams to achieve their objectives, then they are more likely to help you get what you need.

    Remember your residents. Your organisation will have data about your properties, but you may have less knowledge of your residents. Taking time to listen to residents’ experiences of living in your homes will help you pinpoint the types of retrofit measures that will meet their needs and build buy-in to your project.

    Don’t let perfect be the enemy of good. Data is never perfect. It is easy to get side-tracked into chasing small pieces of information which won’t have a big impact. Take steps to improve your data but recognise and record the limitations of your data and assumptions in order that the project can progress.

    Deep dive

    What is meant by good quality data?

    The best definition of good quality data is one which helps your organisation to create “a single version of the truth”.

    The features of good quality data would include:

    1. Data stored in a centralised database

    2. Data in a consistent and easy-to-use format

    3. Data that is frequently maintained so that it is up-to-date and reliable

    4. Clean data to improve accuracy and ease of use

    5. Trusted collectors or providers of data

    6. Flags on data to indicate where there might be lower confidence levels in some of the data

    7. Plans in place to keep data up-to-date

    HACT publishes the UK Housing Data Standards; these are available free of charge at (registration required). The Standards have been developed in collaboration with housing providers and include the following use cases:

    1. Voids and allocations process

    2. Core customer data

    3. Reactive repairs

    4. Asset maintenance

    5. Care and support

    6. Income and service charge collection

    The Data Governance Institute has published a Data Governance Framework to help organisations map out their approach to data.

    Types of data

    In this section, we set out some of the types of data which can help to underpin retrofit projects. This data may be held in different parts of your organisation – or may not have been collected before. Each data set will contribute in a different way to building an understanding the current energy performance of your homes and the potential for retrofit measures.

    Data set


    Stock data

    A breakdown of all your properties’ characteristics, from construction age, dwelling type (house, flat etc), interior details such as heating and hot water system, insulation and common parts; exterior details such as roofing and damp proofing.

    Energy Performance Certificate (EPC) data

    An EPC gives a property an energy efficiency rating from A (most efficient) to G (least efficient) and is valid for 10 years. It also describes levels of insulation, the efficiency of heating and hot water systems and types of glazing and lighting.

    Standard Assessment Procedure (SAP) scores

    EPC ratings are derived from SAP scores. SAP quantifies energy performance in terms of energy use per unit of floor area and are based on estimated annual energy use for space heating, hot water, ventilation and lighting.

    Asset renewal data

    When assets such as boilers are replaced, there should be a record of what was installed and when. This should give a history of the systems in a property and an indication of when it is next due for renewal.

    Repair records

    This is a list of all the repairs that are needed for your properties, including what the repair is, when it will take place and the cost.

    Planned / cyclical maintenance

    Again, planned and cyclical maintenance programme information will give you a sense of which properties are scheduled for improvements, what those works are and when they will take place.

    Complaints data

    Residents have the best insights into their homes. Complaints records can give you an insight into specific properties and may also suggest patterns across an estate or dwelling type where a larger retrofit programme could be beneficial. Some complaints will be clearly connected to the retrofit agenda (for example, a heating system that is unreliable) whilst others may be expressed differently (for example, complaints about damp and mould which suggest that the home is cold).

    Data about your residents

    It is important to think not only about your properties but also about the people who live in them. Household size and composition, occupancy patterns, physical and mental health and household income are all important factors in how people use energy in their homes. You may want to prioritise different types of resident in your retrofit programme (for example, people with health conditions made worse by living in cold homes) and you will need some way of assessing this.

    Tenancy records

    Higher turnover rates or levels of arrears in homes can be a sign that there are issues which make the home less comfortable and more expensive to live in. As well as using this information to target properties for retrofit, these issues can help inform development of a business case.

    Data collection

    Some of the data sets referred to above will be held by your organisation; it’s likely that they are held by different teams or departments. This means that you will need collaboration from others to bring relevant data sets into one place and into the same format.

    There are different methods of collecting your data on building performance:

    1. Building surveys

    2. Thermal imaging surveys

    3. EPC register

    These differ in accuracy, time spent and cost so it is worth understanding the strengths and weaknesses of each.

    Building surveys and thermal imaging surveys provide more reliable and accurate data but are more costly and time-consuming. Ensuring data can be collected during any planned or reactive maintenance works can help to reduce costs.

    The EPC register can be useful if you don’t have other data available. However, EPCs alone are not good enough for retrofit planning:

    1. They are often out of date

    2. EPCs were not designed for net zero carbon planning

    3. There are issues with data quality (for example, estimated data)

    You should ensure that people collecting building data are well trained and skilled. This can include trained internal or external surveyors, retrofit coordinators or qualified members of RICS. Energy Performance Certificates can only be produced by qualified Domestic Energy Assessors; again, you may have these skills within your organisation or work with an external provider.

    If you are collecting data about residents, you will need to ensure that you comply with the data protection and privacy requirements of the General Data Protection Regulation (GDPR). These should already be in place within your organisation as you deal with your residents’ personal data. You will need to think about data collection, how the data will be used (processing), data storage (security and duration) and how you will respond to enquiries from residents about their data. These will all be part of your organisation’s data protection policies and procedures, so a good first step is to speak with the person responsible for data protection and agree a compliant approach.

    If your retrofit project is externally funded – for example, by the SHDF or LARS – there may be monitoring requirements which involve third parties contacting your residents (eg, research or evaluation companies). You will need to get explicit permission from residents for this to happen. The SHDF Competition Guidance sets out initial requirements for monitoring and evaluation which you should consider when looking at your data needs.

    Organising your data

    It is vital to have good quality and timely housing stock data for stock analysis. This means pulling together all the data you have across different departments into one place. A way to do this is to have a centralised database that will help you to create a ‘single version of the truth’.

    Things to consider when creating a centralised database and improving data quality:

    1. Making sure there are dedicated resources to manage and maintain the database (i.e., a data steward)

    2. Digitalise your data – once you’ve collected your data, make sure to store this electronically

    3. Ensuring you store all data in the same format

    4. Organise your data to have clearly defined column and row headings and a shared variable to link all the datasets, e.g. unique reference property number (UPRN)

    5. Keep the database up to date to improve reliability

    Preparing your data

    Before analysing your data, it is worth spending time organising the data and doing some initial cleaning to improve the data quality. Setting up standardised checks is useful. This should include:


    Purpose of the check


    Logic checks

    Checking that combinations of data points are logical and reasonable

    For example, floor area data. Does this align with what you know about the property type?

    Consistency checks

    To determine whether dataset points are consistent with other datasets

    For example, is the property’s EPC rating consistent with your asset register? There might be a mismatch if a heating system has been upgraded but no new EPC produced.

    Plausibility checks

    To determine if the dataset point is appropriate and within the expected range

    Look for extreme highs and lows in the data. Are these appropriate? For example, are instances of extremely high or extremely low energy use likely to be true?

    Zero or null values could be a strong indicator of a data quality issue.

    Sometimes outliers are giving you a true picture, so do not assume that they are mistakes in the data.

    When you come across an error, your first step should be to generate new and accurate data (for example, by carrying out a survey of the building in question). Given that this is likely to be time-consuming, you could also manually change the data to something more plausible whilst you await up to date information and flag this so the quality issues can be seen by others. If you make manual changes, you must keep a log of these changes and set a plan for improving data quality at a later stage. (By way of analogy, think about energy bills that rely on estimated data – the longer that the estimates go on, the further they get from the truth about what is happening. Only a meter reading can set things straight.)

    It is up to you how far you take this step; the more data cleaning you do, the better quality the data is. It takes extra effort but makes analysing your data easier and gives better results.

    Further resources

    What data standards are there for housing provider?

    UK Housing Data Standards, HACT – these standards have been developed in collaboration with housing providers and are widely used across the sector. They include standards for repairs and asset maintenance and a range of other service areas. They are free to download although registration is required.

    How can I think strategically about data for my project?

    Data Governance Framework, Data Governance Institute – this framework sets out ten considerations for effective data governance. It’s a helpful set of principles, designed for an organisational approach to data, that can equally be applied to thinking about your retrofit project.

    View Website (

    What are the rules about managing resident data?

    Guide to the UK General Data Protection Regulation, Information Commissioner’s Officer – an helpful web guide to the GDPR, which governs the use of personal data. As a start, you should certainly review the sections entitled “What is personal data?” and “Consent” as these will be important in your project. GDPR compliance is important to protect the privacy of individual residents, and you should be sure to work with your Data Protection colleagues to ensure that your project is compliant.

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    Get in touch

    If you would like to discuss planning issues on your retrofit project, please contact the RISE Support team -

    We would love to hear about your experiences. What has worked for your organisation? What lessons have you learned? What documents, reports or tools have you found most helpful? Please contact if you would like to share your experiences.

    Deciding target outcomes

    Once you have conducted your stock analysis, you will have an idea of your housing stock’s baseline energy efficiency performance. You must then decide the target outcomes for your retrofit project. What performance do you expect from properties after retrofit? This exercise is informed by your baseline, strategic objectives and guidelines set out by funders. It will allow you to produce a set of targets that inform your business case and funding proposal.

    Why it matters

    Clear and measurable targets for your retrofit programme allow you to create a high-level delivery plan and decide the most suitable procurement approach.

    Key steps to take

    1. Understand the strategic context for your project – for example, your organisation’s goals related to net zero or fuel poverty and wider ambitions within the local area

    2. Understand the key drivers for your specific project – how does your project fit within your asset management strategy? What does the project need to achieve to open up different funding opportunities?

    3. Understand how your targets will drive your retrofit approach,  and vice versa. There is an interplay between your approach to retrofit and your targets. For example, you may be trying to improve the average EPC across your whole stock by retrofitting as many homes as possible. Alternatively, you may be trying to retrofit a small number of properties to the highest levels of energy efficiency. Your project goals and your targets need to be compatible.

    4. Set targets that are achievable and measurable.

    5. Set out how you will measure and monitor the impacts of your retrofit project.

    Success factors

    Understand the strategic fit - A project that clearly aligns with the objectives of your organisation, and your consortium is more likely to gain senior management support and to be replicated in future once successful.

    Align with funders’ needs – External funders will have criteria by which they measure the effectiveness of their funding, for example, tonnes of CO2 saved for every £ invested. Your project plan will need to show how you expect to meet these criteria.

    Maximise the co-benefits – Retrofit can achieve a great deal more than carbon reduction, for example, improvements in health and wellbeing for residents or an increase in local employment opportunities. Make sure that you map all of the potential benefits that the project could deliver.

    Know the limits of your project – Whilst retrofit can deliver a great deal, you should always be mindful of the limitations of your project. If you set too many targets, your project will become unfocused. A core set of goals and targets will give you a strong steer and clear messages for your partners and funders.

    Make sure you can measure what you achieve - Our guidance on Monitoring and Evaluation Strategy sets out different approaches to this crucial activity. This will take time and resource after the retrofit measures have been completed and you will need to include this in your project plan.

    Deep dive

    Understanding the context

    The key policy and legislative drivers for reducing carbon dioxide emissions are:

    • The Paris Agreement aims to limit global warming to well below 2 degrees Celsius above pre-industrial levels; ideally below 1.5 degrees Celsius. Many organisations have set carbon reduction targets to align with the Paris Agreement. The Science Based Targets Initiative provides a useful framework and background guidance for looking at your organisation’s goals alongside the Paris Agreement.

    • The Climate Change Act 2008 set out the UK’s goals for carbon reduction. It was amended in 2019 to set a more ambitious “net-zero” goal, requiring the net UK carbon account for the year 2050 is at least 100% lower than the 1990 baseline.

    • The Heat and Buildings Strategy sets out some of the government’s approach to getting to net zero, including an ambition to phase out gas boilers and increase the deployment of heat pumps.

    Setting targets

    Targets will usually be driven by Government policy and/or your organisation’s corporate strategy. Some of the more common targets in housing retrofit are:

    • Reducing carbon dioxide emissions from energy use in your homes

    • Eliminating fuel poverty – for example, by achieving EPC C by 2030

    • Reducing the heat demand in properties (usually measured in kWh/m2/year)

    • Completing a measured-based retrofit programme based on certain types of funding available

    Two main performance requirements of Wave 2.1 of the Social Housing Decarbonisation Fund were:

    Applicants must improve stock using a fabric first approach to at least Energy Efficiency Rating (EER) C, with some exceptions for EER F/G homes.

    Consideration should be given to improving properties to a space heating demand level of 90 kwh/m2/year where reasonable and cost effective.

    Maximise the co-benefits

    Our guidance on Building a Business Case includes discussion of the wider co-benefits of retrofit and energy efficiency. These include:

    • Benefits to your residents – including improved health and wellbeing from living in warmer homes and financial benefits from reduced energy costs

    • Benefits to your organisation – such as reduced maintenance and service costs, improved understanding of your homes, improved customer satisfaction and reduced voids

    • Wider social or community benefits – such as local skills, training and employment opportunities and improved community cohesion

    In some cases, you may wish to set targets for these. For example, you could use your procurement process to set goals for your contractors in terms of local apprenticeships. You could also use resident surveys to measure quality of life or general wellbeing before and after the retrofit project.

    Further resources

    How can I set targets to reduce fuel poverty?

    Rising to the EPC C Challenge, National Housing Federation – this useful article sets out some of the key practical considerations when thinking about achieving an EPC C target.

    How do I find out about setting heat demand targets?

    The key to reducing heat demand is to take a “fabric first” approach, by making sure the building envelope (walls, roof, floor, doors, windows) is thermally efficient or well insulated. The fabric first stage is then followed by efforts to decarbonise the property’s heating. Some initial resources on reducing heat demand can be found at:

    Whole House Retrofit, Retrofit Academy – this guide sets out the philosophy behind a fabric first approach and how it can help you to set heat demand targets.

    Where can I learn more about the co-benefits of retrofit?

    Climate Action Co-Benefits Toolkit, Ashden - this is a great resource for understanding the wider benefits of carbon reductions, including those from retrofit. It includes examples and figures for some of the wider co-benefits of retrofit and links to sources of local information that can help you build your business case. Whilst the toolkit was written for local authorities, it’s an invaluable resource for any organisation looking at retrofit projects.

    The International Energy Agency has also produced analysis of the wider benefits of energy efficiency, incorporating some of the themes outlined above as well as air quality, energy access, energy security and productivity gains.

    Regeneration and Retrofit, UKGBC – this report gives examples of how local regeneration can be aligned with retrofit to promote employment opportunities.

    How can I think about net zero in the context of new build and existing properties?

    The UK Green Buildings Council has developed a framework definition for net zero carbon which sets out ways of thinking about carbon reduction. It includes consideration of construction so can help you think about new build homes as well as your existing stock.

    View Website (

    Get in touch

    If you would like to discuss ways of deciding target outcomes for your retrofit project, please contact the RISE Support team

    We would love to hear about your experiences. What has worked for your housing association? What lessons have you learned? What documents, reports or tools have you found most helpful? Please contact if you would like to share your experiences.

    Selecting target properties

    Once you have the performance baseline of your properties through stock analysis and decide your target outcomes, you will select the properties to retrofit.

    Why it matters

    A selected group of target properties will enable a preliminary design for your project. This will inform your procurement strategy and your business case.

    A robust, repeatable approach to selecting properties for retrofit enables successful scale-up into later projects. This may involve a long-term prioritised plan for your stock and a short-term focus for funding proposals.

    Key steps to take

    1. Understand the target outcomes that you are trying to achieve. 

    2. Carry out your stock analysis so you know where you are starting from and the opportunities that are available. Explore our toolkit on Data for Retrofit Projects to help with this step.

    3. Decide your method for selecting properties – whether data-led, resident-led, area-led or a combination (see more on this below)

    4. Test some scenarios – it is worth testing a few scenarios, especially if you have several options available (eg, different estates that you could retrofit). You may find that taking a different approach helps you achieve your target outcomes more effectively. This will also give you flexibility to try different options when you develop your Business Plan.

    Success factors

    Lay the groundwork first – you will need to know what you want your project to achieve (your target outcomes) and have an understanding of your housing stock through stock analysis before you can select properties

    Use the knowledge within your community – Your colleagues and your residents will have a deep and often detailed understanding of your housing stock. This real-world insight – which homes are hardest to heat, which residents are struggling most to pay their bills - can bring data analysis to life and begin to shape your ideas into a retrofit project that will make the biggest impact.

    Try some different options – testing some scenarios will help you understand which combination of properties will achieve the target outcomes for your organisation, consortium or funder. You may find that different combinations of properties allow you to go back and revisit your target outcomes.

    Be clear on how you are selecting properties – your process should be logical and transparent so that you can explain clearly to your organisation and your residents why certain properties have been selected and others have not. Your method of selecting properties needs to align with your organisation’s strategy.

    Think about the future – is your method of choosing properties suitable for the delivery of your long-term strategy? You can use an approach that just suits the needs of an immediate funding opportunity, but you are more likely to sustain momentum and senior level buy-in if you can have a consistent approach over time.

    Deep dive

    Property selection – an overview

    There are several ways to select properties. Your approach will depend on:

    • The quality of your stock data. For example, if your energy data is incomplete, it may be more suitable to target a geographical area where there is a high level of deprivation.
    • Your experience in retrofit. Targeting properties with simpler archetypes (eg, semi-detached houses) may be a good place to start.
    • Your organisation’s future retrofit targets and ambitions. Bringing low-quality stock to the highest level of performance requires careful modelling and costing.
    • Conditions of funding bids, including the needs and ambitions of other consortium partners.

    Taking a data-led approach

    Your energy analytics software can help with property selection. You can model around a range and combination of factors.

    Factors to consider include:

    • Age – Older properties are more likely to be less energy efficient. This might include buildings with solid walls, for example.

    • Property type – Specific building archetypes in your stock may suggest standard solutions applicable to a large number of properties—for example, combustible cladding on apartment blocks that needs replacing.

    • SAP scores or EPC rating – You could filter properties with low EPC ratings and map them to see if they form a cluster, suggesting an area-led approach.

    • Annual carbon impact – You might target properties with the highest carbon emissions.

    • Location – Map the low-performing properties with a particular property archetype – for example, F and G rated properties in a specific neighbourhood. This helps create geographic clusters that you can tackle in an integrated way.

    • Measure-based approach – Review your asset renewal plans and choose to carry out your retrofits simultaneously with these repairs or replacements. This can help you align retrofit costs with existing asset renewal budgets.

    • Right to buy – where homes are subject to Right to Buy you might decide to exclude them from large scale investment.

    You can also consider ways of using your data in collaboration with other local authorities and housing associations to:

    • Develop joint bids for funding (which may be a funder’s requirement

    • Promote a neighbourhood approach

    • Generate greater social impacts

    • Generate economies of scale

    Taking a resident-led approach

    Residents know their properties the best. They live in the homes and know how they operate day-to-day.

    Residents should always play a part in property selection. This will be particularly important in a community based retrofit project. Engaging with existing groups, such as repair panels or resident associations, can help you to define a project that responds to people’s needs.

    Housing stock in a neighbourhood will be across multiple tenures and this can have an impact on your property in terms of:

    • Resident engagement – you will need to think about how you engage with leaseholders, private landlords, private tenants and owner occupiers within an area

    • Project funding – will external funders support works to private sector properties? If not, how will these works be funded?

    • Project delivery – are there considerations around how and when your project can be delivered if you are working across multiple tenures? Will you receive senior level support for this activity or will it need to be contractor- or local authority-led?

    • Taking an area-led approach

    Your organisation may have clusters of properties on streets and estates that can be wrapped up into retrofit projects.

    Selecting properties on this basis will generate economies of scale; this can particularly be the case if you can capitalise on trigger points in existing programmes, for example by installing roof installation as part of cyclical roof repair / replacement programmes.

    An area-led approach can also promote economic growth and local job creation which adds weight to funding bids.

    Get in touch

    If you would like to discuss ways of selecting target properties for your retrofit project, please contact the RISE support team -

    We would love to hear about your experiences. What has worked for your housing association? What lessons have you learned? What documents, reports or tools have you found most helpful? Please contact if you would like to share your experiences.

    Preliminary design

    Once you have defined your target outcomes and selected a set of properties for the project, the next step is to think about your general approach to retrofitting. This is not a detailed design but a first pass to see what is feasible. It will suggest possible packages of measures to reach the target outcomes. A rough test of economic viability and a risk assessment will help focus on the best options for the selected properties.

    Why it matters

    The preliminary design lets you explore different options for retrofit and consider all the foreseeable opportunities and barriers. It is built on reality, taking account of the site context and any known existing defects, in order create a suitable plan for your properties.

    If the right considerations and decisions are made at the beginning of the project, then this will avoid costly consequences further down the line, including serious and detrimental building defects which could have an impact of residents’ health, safety and wellbeing.

    Key steps to take

    1. Compile existing data: Review any existing data on the property including EPCs, existing defects, construction type etc. This will allow the feasibility of the project to be explored.

    2. Assemble the right project team: You may need to appoint a retrofit coordinator and assessor under PAS2035 – this is a requirement of most publicly funded programmes. Even if these roles are not mandatory, you should consider appointing a retrofit coordinator, architect or RICS surveyor to consider all aspects of the retrofit project and ensure smooth coordination.

    3. Consider the site context: Think about ease of access, planning context, heritage context, flooding, biodiversity etc. This can all feed into the feasibility study when considering barriers and opportunities.

    4. Establish whether the project needs to comply with PAS2035: If the project is to be delivered through the SHDF, ECO or many other publicly funded programmes, then it will need to comply with PAS2035. This will affect the process that needs to be taken and the project team required.

    5. Check your objectives and intended outcomes: Review the project requirements against your objectives to make sure they are aligned.

    6. Establish the level of disruption that is acceptable: The retrofit approach taken will depend on how much disruption is acceptable. For example, do the buildings need to remain occupied during the works or can they be vacated for a certain amount of time?

    7. Consider project budget and funding: It is imperative to set a project budget and to source enough funding for the retrofit as this will determine what is possible for the project. Read more about this in Building A Business Case.

    8. Think about potential contractors and ongoing maintenance needs. You may have existing contracts with suppliers that can install measures but you will need to ensure they have the right qualifications and accreditations. You will also need to think about the internal or external expertise that you will need to maintain any new systems or components.

    Success factors

    Ensure the building is “retrofit ready”: Existing defects such as structural issues, asbestos, drainage issues and damp need to be highlighted and rectified before starting the retrofit project.

    Consider the whole house: All retrofit projects should consider the whole-house (that is the complete building envelope, heating, ventilation and energy systems) and not just individual elements. The retrofit measures don’t have to be delivered all in one go, but you will need a considered phasing strategy in place to avoid incorrect sequencing.

    Use “fabric first” principles: Fabric first principles are based on reducing the heating demand of the property first, before installing a new heating system or energy systems. This will avoid the heating system being oversized or inappropriate renewable energy systems being installed.

    Consider the options: There will be lots of options available for retrofit, and different combinations of measures available. Carry out an options appraisal to consider different strategies before deciding on the best way forward.

    Appoint specialists: The key to a good retrofit is having the right project team in place with the specialist skills required. For example, if the building is historic, then a historic building specialist will be required. 

    Have a medium-term plan: The ultimate aim with retrofit is to achieve net zero carbon by 2050, therefore each property should have a plan for how this will be achieved. Phased retrofit measures can then align with this plan and allow a fully coordinated approach.

    Deep dive

    Before starting your a retrofit project

    Before starting your project, you will need to check whether the property is “retrofit ready”. Any existing defects such as structural issues, drainage issues, damp, timber rot or presence of asbestos should be rectified first.

    Key issues relating to the site context should be established such as Planning Permission, flooding, Listed Building Consent, Conservation Area Consent, access arrangements etc. Our guidance on Identifying Planning Constraints has more information on this.

    The age and construction of the building should also be reviewed. If the building is traditionally constructed or protected, then you will need to appoint a specialist in historic buildings before deciding on any retrofit measures. Likewise, if the building is of non-traditional construction then a specialist designer should be appointed. Traditionally constructed buildings (prior to around 1919) and non-traditional construction in the 1960s and 1970s act very differently to more modern or conventional buildings in terms of their moisture balance, so it is imperative that this is considered from the start of the project.

    Key retrofit principles

    The retrofit approach should be based on “fabric first” principles, which focuses on firstly improving the building fabric to reduce the heating demand as much as possible, followed by installation of low carbon heating systems and renewable energy systems.

    Any retrofit project should consider the whole house, and not just one element; this will primarily include all elements of the building envelope as well as heating, ventilation and energy. There are two approaches that can be taken for implementation of measures as below:

    • ‘Deep’ retrofit: all energy efficiency measures are installed at one time. This means one major overhaul of the property and a relatively high one-off cost. This would likely mean fewer properties treated per year but improving those treated to a very high level of carbon reduction and comfort.

    • Phased retrofit: application of different measures at different times. This approach would create more potential points of disruption, but would enable more properties to be gradually improved at the same rate, and allow retrofit measures to be timed with planned works. This approach would allow costs to be spread out over different annual budgets as well an opportunity to maximise external funding and income sources and will likely be the most suitable approach to most of the existing housing stock. It is important that phased works are correctly sequenced to avoid unintended consequences; an appropriate medium-term plan should be put in place for each property in line with the guidance set out in PAS2035.

    Potential retrofit measures

    Retrofit can effectively be split into the following three steps:

    Step 1: Reduce the demand for energy by improving the building fabric: Typical interventions for cutting heat loss through the building fabric are:

    • Addressing draughts (draught-proofing) to increase airtightness. The main sources of draughts are windows, doors, and floors.

    • Where you have solid external walls, consider external wall insulation or internal wall insulation.

    • Where you have cavity walls that are not filled, or filled with defective material, consider cavity wall insulation.

    • Loft insulation, pitched roof insulation or flat roof insulation will reduce the significant heat loss from roofs.

    • Replacing doors and windows to meet high thermal efficiency standards. Measures include double/triple glazing and high-performance doors.

    • Floor insulation is a good way to reduce heat loss. However, different approaches are needed for suspended and solid floors. Insulating solid floors can be very complicated.

    • It is essential that all elements of the building fabric are considered as part of the strategy in order to create a full consistent external envelope. Failure to do so will result in cold spots or thermal bridges which can lead to condensation, damp and mould.

    As you are increasing the airtightness and reducing heat loss in your properties, it is essential to consider the impact this has on air movement and the risk of condensation and mould. You need a ventilation strategy for each measure, or group of measures, to mitigate risks.

    Step 2: Install a low energy heating and hot water system: Once the demand for heat has been reduced as much as possible, evaluate options for low carbon heating:

    • The most common sources of clean heat are heat pumps. These can be either air source (ASHP) or ground source (GSHP).

    • Connecting into a local heat network could also be an option to explore.

    • Solar thermal heating for hot water can also be an option where roof space permits.

    • Where renewable sources of heat are not an option, highly efficient electric heating can be used, such as high heat retention storage heaters.

    Step 3: Decarbonise the energy supplied to the property: Finally, for any residual carbon, there are renewable systems for generating electricity:

    • If the building is suitable, you may be able to install solar photovoltaic (PV) panels.

    • Batteries may be installed along with solar PV to store power for use when solar generation is low. This allows residents to get the maximum benefit from solar PV.

    Further resources

    How can I learn more about different retrofit and decarbonisation measures?

    Many resources go into detail on how to identify suitable measures, the benefits to residents (and landlords) and the interaction of certain measures with others.

    The Energy Saving Trust provides measure by measure guides that are useful for internal staff and for residents who may be need some extra information about retrofit.

    How do I learn more about traditional or historic buildings?

    Guidance Wheel, Sustainable Traditional Buildings Alliance (STBA) - A very useful tool for creating packages of measures for older or historic properties is the Guidance Wheel from the Sustainable Traditional Buildings Alliance (STBA). The wheel highlights the benefits of and links between different retrofit measures and considerations and concerns around technical, heritage and energy issues.

    What are the requirements in PAS2035?

    The Retrofit Academy has guidance on fulfilling the requirements of PAS2035 and the retrofit process with a focus on the whole house approach.

    What standards can I use for deep retrofit?

    Passivhaus have a standard called EnerPHit, which is a very high standard of retrofit based upon fabric-first principles.

    How can I find retrofit specialists for my project?

    Trustmark has detailed guidance on the whole house approach as well as a database of Retrofit Coordinators, Retrofit Assessors and accredited Installers.

    Get in touch

    If you would like to discuss design considerations for your retrofit project, please contact the RISE support team -

    We would love to hear about your experiences. What has worked for your housing association? What lessons have you learned? What documents, reports or tools have you found most helpful? Please contact if you would like to share your experiences.

    Risk assessment

    Achieving a successful retrofit is not just about improving the energy efficiency of the building fabric, or using low/zero-carbon heating, or providing renewable energy. It is about a balanced set of measures and systems that work together to improve energy performance, reduce carbon emissions and provide greater comfort at lower cost to residents. Each of these outcomes can be at risk if your project is not well-planned or executed. These risks need to be managed throughout.

    Why it matters

    Get the balance right and your retrofit project can deliver great outcomes. Get the balance wrong, and the retrofit can end up creating more problems than it solves. Once you have your initial design thoughts, carrying out a risk assessment can spot incompatibility between the various parts of your retrofit package.

    Key steps to take

    1. Review the table of energy efficiency measure interactions in PAS 2035. Do you have riskiy combinations of measures in your design? Can you adjust the design to reduce risks?

    2. Think about the retrofit plan. List everything that could go wrong and what the impact would be.

    3. Use this data to build a risk register describing:

      1. The risk.

      2. The impact if it happens.

      3. How likely is it to happen?

      4. What mitigation actions are possible – that is, what can you do to reduce the risk happening or reduce the impact if it does happen?

    4. Focus on the highest impact risks and those most likely to happen.

    5. Update your risk assessment regularly as the project develops.

    Success factors

    Ask people what matters to them – A good risk assessment is not based on one person’s view. It will take account of the perspectives of different people. Your repairs and maintenance team might have a different assessment of the risks of renewable heating systems, for example. Take time to speak with your residents too – it may be important to them to be able to stay in their homes during the project or to have someone with them when there are people working in the property. Their perceptions of risk will be different to yours and should be included in your plans.

    Take a structured approach – Having a structured approach helps you to be clear with residents, senior management and contractors as to how the project is considering and addressing risks. Transparency is essential so that people can see how risks have been categorised and have the opportunity to add their experiences and insights to the assessment.

    Give it the time it deserves – It can take some time to develop your risk assessment and it’s easy to think of it as a tick-box exercise. One of the lessons of the Grenfell tragedy is that we should always be rigorous in thinking about risk.

    Use the experience of others – Your consortium partners, colleagues, contractors and residents will all have experiences that can be valuable in thinking about how to mitigate risks. You do not have to come up with all of the answers yourself.

    Update, update, update – A risk assessment should be updated repeatedly as a project progresses. There are new and different risks at each stage of a retrofit project and you do not want to be taken by surprise.

    Deep dive

    Risks to residents

    Residents will face some disruption during a retrofit project, whether this is a need to allow the retrofit team into the property, mess and dust, or the upheaval of moving out for a time. All of these can place a physical or mental strain on residents, who will need support and care throughout the process.

    The Grenfell tragedy showed us the most dramatic and devastating risks to human life and health resulting from a retrofit project. Poorly executed retrofit projects can directly impact human health in other ways, particularly where insulation is installed without appropriate ventilation. In these instances, the risks are:

    • Condensation and mould. These increase the risk of a range of respiratory ailments. For people with weakened immune systems, this can be very dangerous.

    • Reduction in the oxygen content and increases in carbon dioxide in the air, particularly in overcrowded properties

    • The build-up of directly toxic materials in the air, such as carbon monoxide, volatile organic compounds (VOCs) and radon

    • Overheating. This is particularly a risk in homes with south-facing glazing and in densely populated areas.

    In addition, residents may find that they do not achieve savings on their energy bills if they have not been advised on how to use their new energy systems or if those systems have been installed or set up incorrectly.

    Risks associated with energy savings

    There is a risk that actual energy savings may be less than expected due to:

    • Inappropriate specification of insulation and substandard installation, leading to voids in the fabric and cold bridges, especially at corners, joints and junctions

    • Low and zero-carbon heating systems not carefully matched to the thermal efficiency of the building envelope

    • Poorly designed heating controls and/or failure to provide residents with sufficient training and support

    • Occupants may choose to take some of the energy savings in increased comfort. This is known as the ‘rebound effect’.

    Risks to the building

    Damage to the building fabric is usually due to excess moisture caused by poor ventilation and cold bridges. Adding new draught-proofing and insulation without considering proper ventilation can result in surface condensation and mould growth. This in turn can trap moisture which damages structural materials, such as rotting in timbers.

    Organisational or strategic risks

    In addition to the specific “operational” risks associated with the retrofit outcomes, there are some broader categories of risk which you will need to consider:

    • Financial risk – as you develop your business case, you will need to be clear on the level and nature of financial risk that your organisation may be taking on with your project. Your initial project may make use of external funding sources, but you will also need to think about how future waves of work will be funded and the likelihood of securing external funding for this.

    • Contract risk – your approach to procurement will introduce discussions around contractual and supply chain risk. In particular, there may be pricing uncertainty about goods or materials required for your project or supply chain risk associated with deliveries of components. You will need to work with your contractors to understand and address these risks.

    • Reputational risk – if residents have a poor experience of the project, there may be reputational risk to your organisation. This might lead to negative coverage in local media or among residents groups online. Working closely with residents throughout the project will help you to understand and manage the risks that matter most to them, and to retain their support if something does go wrong.

    A structured approach to risk assessment

    PAS 2035 provides a standardised approach to carrying out a risk assessment. This requires a Retrofit Coordinator to assess risks for each property or property type on a project giving each a grade of A, B or C. This in turn dictates the retrofit methodology or path that is taken for a project.

    PAS 2035 also includes a table of the interactions between energy efficiency measures. It identifies four types of interaction:

    • Measures that are independent and do not interact with each other

    • Measures that interact or connect and may require specific construction details in design

    • Measures that interact and which will need careful design and specification to make sure they combine positively

    • Energy efficiency measures that should never be used together

    Retrofit Coordinator training includes significant attention to risk assessment and again demonstrates the value of having a retrofit coordinator as part of your project team.

    A thorough risk assessment can prevent problems later in the project and should be updated whenever there are changes to the retrofit plan.

    Further resources

    How can I think about risk at a strategic level?

    Boards of registered providers are responsible for managing the risks their organisations face. The Regulator of Social Housing’s Sector risk profile is intended to help boards have a better understanding of those risks, in an increasingly complex and diverse sector.

    How do different energy efficiency and renewable energy measures interact with each other?

    PAS 2035 provides an Interaction Matrix, described above. You can purchase a copy of PAS 2035 from:

    You can also view the Interactions Matrix as a standalone document at the following link:

    Get in touch

    If you would like to discuss monitoring and evaluation strategies for your retrofit project, please contact the RISE support team -

    We would love to hear about your experiences. What has worked for your housing association? What lessons have you learned? What documents, reports or tools have you found most helpful? Please contact if you would like to share your experiences.


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