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Preparing a retrofit project

8. Understanding PAS2035


PAS 2035 is a new British standard that creates a recognisable quality standard for the retrofit and energy efficiency sector for housing. All projects funded by the Social Housing Decarbonisation Fund, Energy Company Obligation or Local Authority Delivery Scheme will be required to comply with the standard. 



    PAS 2035 is a new British standard that creates a recognisable quality standard for the retrofit and energy efficiency sector for housing. All projects funded by the Social Housing Decarbonisation Fund, Energy Company Obligation or Local Authority Delivery Scheme will be required to comply with the standard. 

    Why it matters

    The new standard aims to ensure that retrofit projects deliver their intended outcomes for the right cost.

    PAS 2035 helps ensure the right design for a project, so that the right measures are installed in the right circumstances. It also reduces the “performance gap” of energy savings not being delivered in practice, limiting the chance of defects and unintended consequences such as damp and mould. This in turn gives residents a more realistic picture of cost savings on their fuel bills and a more comfortable and healthy living environment as a result of retrofit. This means that your housing association can be assured that retrofit projects are being delivered as expected, within a trusted framework and with an eye to developing a longer term programme of works.

    Key steps to take

    1. Get informed: Get to know the process of PAS 2035 and what’s involved through further resources (see below), attending training and talking to other housing providers who have started using the standard.

    2. Identify your properties. Before you embark upon any retrofit project, you should firstly identify the properties and ensure they are retrofit ready. You can read more about this in our Retrofit Interventions guidance.

    3. Create your team. You will also need to appoint the right team, which you may wish to do in-house through relevant training. The roles required by PAS2035 are as follows:

    • Retrofit coordinator

    • Retrofit assessor

    • Retrofit designer (often an external design consultant)

    • Retrofit installer (usually an external contractor)

    • Retrofit evaluator

    1. Focus on the retrofit coordinator. The role of retrofit coordinator is needed for all retrofit projects under the funding streams listed above. You may want to build this capacity in-house, especially if you expect to build a programme of retrofit projects over a period of time. If this is not for you then you can find retrofit coordinators through TrustMark - Find a Tradesperson.

    Success factors

    Make a plan: Assess and organise your property portfolio and highlight which properties are retrofit ready, which ones should be tackled first, which ones have already had energy efficiency measures installed etc.

    Make sure properties are retrofit ready: Property defects should be rectified before embarking on any energy efficiency measures. This means they should be structurally sound, watertight, dry, safe and have adequate drainage/services.

    Start small: You may wish to start on one pilot project rather than going straight in at the deep end so that you can experience the process and see more clearly what’s involved.

    Fabric First: The principles followed by PAS 2035 are “fabric first” which is using energy efficiency measures such as the addition of insulation and better windows to reduce the heating demand first, followed by low carbon heating and renewable technology. This will ensure that low carbon heating systems can be appropriately sized and work in their optimum efficiency.

    Build tight, ventilate right: In line with the “fabric first” principle, retrofit projects should aim to increase air tightness along with the right ventilation, which will reduce heating demand, improve thermal comfort and reduce health risks to occupants.

    Consider the whole house: Retrofit measures shouldn’t be seen as individual measures, but part of a whole property system. Every retrofit measure carried out needs to be considered as part of the whole house system to avoid unintended consequences, e.g. insulation shouldn’t be installed without making sure there is adequate ventilation to the property.

    Follow the plan… but be flexible: The PAS 2035 process will ensure there is a “medium term plan” for each property over a period of around 30 years – this will ensure that the right sequencing of measures can take place for the property. However, the plan can be adapted in conjunction with your retrofit coordinator to incorporate funding opportunities or asset management objectives.

    Feedback: Each retrofit project provides an excellent opportunity for learning and feeding back key lessons into future projects.

    Deep dive

    The PAS 2035 standard is a lengthy and complicated document. However, it all comes down to the six steps explained in the table below:

    PAS2035 Process Explained

    What does it mean?

    Who does it?

    Step 1: Intended Outcomes 

    The intended outcomes are what you want to achieve with the retrofit project and what is important to your organisation, for example, reducing carbon emissions, reducing residents bills, increasing SAP ratings.

    The retrofit coordinator will help you to understand your goals and ensure that these form the basis for the project.

    Step 2: Risk Assessment 

    The project risks depend on the expected works that will take place. Different levels of risk will be managed differently and have different requirements under PAS 2035.

    The retrofit coordinator will review the intended outcomes and likely retrofit measures and will assign a risk path to the project.

    Step 3: Whole Dwelling Assessment 

    This is a thorough assessment of each property (generally using SAP or PHPP) which will provide accurate information and enable the right decisions to be made.

    A retrofit assessor will carry out the assessment.

    Step 4: Design and Coordination

    All the information is gathered together and a 30-year retrofit plan is created for the property, followed by a design.

    The retrofit coordinator and assessor will create the retrofit strategy and a retrofit designer will carry out the design.

    Step 5: Installation

    The installation will take place by a Trustmark certified contractor in accordance with British Standard PAS 2030.

    A retrofit installer will carry out the installation and will be monitored by the retrofit coordinator.

    Step 6: Monitoring and Evaluation

    The retrofit project should be monitored and evaluated in order to measure its success and provide key learning opportunities.

    A retrofit evaluator will carry out the evaluation of the retrofit.

    Further resources

    Where can I find PAS 2035?

    PAS 2035 is published by BSI and is available for purchased at the link below. Purchasing PAS 2035 also gives you access to PAS 2030, which is the related standard for installation of energy efficiency measures. (If you are planning to retrofit park homes, you should also search the BSI shop for PAS 2031.)

    Visit Website (

    Where can I find retrofit coordinators and other suppliers?

    PAS 2035 has been fully incorporated into Trustmark, the government-endorsed quality scheme for companies providing retrofit and energy efficiency services. Trustmark holds the database of all registered people and companies who operate within the PAS 2035 including retrofit coordinators, assessors, installers and evaluators.

    Visit Website (

    Elmhurst and Stroma also offer accreditation to retrofit coordinators and assessors and hold databases of registered persons.

    Where can I learn more about PAS 2035? Where can I find training for retrofit coordinators?

    The Retrofit Academy offers training to individuals who wish to become retrofit coordinators and also have lots of information and videos to explain PAS2035 in further detail on their website.

    Get in touch

    If you would like to discuss ways of addressing PAS 2035 in 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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