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Retrofitting the UK’s housing stock is an essential process that needs to happen if the UK is to reach net zero by 2050. It is fundamental to achieving Government’s climate and fuel poverty polices. Reducing emissions from the UK’s buildings is one of the great challenges of the net-zero transition.


Britain’s 26 million existing homes are responsible for around 23% of the UK’s carbon emissions. 


Retrofitting typically involves a significant improvement in the thermal performance and comfort of a home or public building by understanding and improving the fabric of the structure.

Retrofitted house = homes with less maintenance issues and lower energy bills

Get Retrofit Ready

Buildings function as a whole, sensitive to changes that happen within them, so planning retrofit and maintenance measures in isolation rather than as part of a joined-up process risks incurring unintended consequences, such as inappropriate insulation specification and positioning leading to moisture degradation of a building fabric. 


LEAF is here to provided solid guidance to those seeking to navigate the journey towards energy reduction and decarbonisation in existing buildings. Before you embark on the retrofit journey you will need to ensure your building is 'Retrofit Ready' as simple maintenance can increase both internal comfort and the fuel efficiency of the building, as it allows the building to work as effectively as possible. For instance cracks in the render may contribute to damp, which in turn will lead to mould growth.

Maintenance makes your building ‘retrofit ready’ and should be done before undertaking larger measures.


Access the LEAF Retrofit Ready guide and see what you can do to start the journey.

Download the LEAF Retrofit Ready Guide

Click here to download

LEAF Retrofit Approach 

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LEAF provides whole house improvement plans generated from a holistic building approach. We only work with experienced architects to tailor procedures and put recommendations through enhanced software and hardware analysis to ensure that retrofit is done right once, to reduce risk of future maintenance expenditure (we diplomatically call this unintended consequences).

The general consensus is, that when it comes to Retrofit, there is not one size that fits all. The LEAF process allows clients to consider cost options and weigh up potential outcomes. In this way both public & private sectors as well as home owners can find a tailored solution which suits their specific needs.

PAS2035 & 2038

PAS 2035:2021  is the new over-arching document in the retrofit standards framework introduced following the recommendations of the Each Home Counts review, sponsored by the Department for Business, Energy and Industrial Strategy (BEIS) to deliver a standardisation for all retrofitting projects. PAS 2035 essentially provides a specification for the energy retrofit of domestic buildings, and details best practice guidance for domestic retrofit projects. PAS 2038 applies to non-domestic buildings. However, not every non-domestic building will follow PAS 2038.

Without this standard there is a concern that a rush to retrofit could lead to rushed, impartial solutions with unintended consequences. Examples could be ASHP installed before basic draft proofing and insulation measures are undertaken. Or inappropriate insulation specification and positioning leading to moisture degradation of building fabric.  

The Retrofit Standards Framework, underpinned by PAS 2035 and PAS 2030:2019, provides a clear and methodical approach for this work, helping to ensure that all improvements are carefully considered in relation to the characteristics of each project and that best practice knowledge is passed on through the industry. By embracing this approach, industry professionals can ensure they are prepared for the challenges of delivering retrofits that perform as expected and deliver long-term value. 

Use of the PAS will also contribute to the protection and enhancement of the architectural and cultural heritage of our building stock and ensure that retrofitters avoid unintended consequences related to any of the above.

Roles within PAS 2035

A number of professional roles have been created within PAS 2035, including that of Retrofit Advisor, Retrofit Assessor, Retrofit Coordinator, Retrofit Designer and Retrofit Evaluator. It is not necessary that all of these roles are carried out by separate individuals, as long as whoever carries out each role has received the levels of training and certification required by PAS 2035, and that they are impartial. 

LEAF Process

Our LEAF process will provide you with three reports, depending on the level of service you require. They recommend changes which range from simple to Whole House solutions that can done immediately or over the course of 25 years. The recommendations are all tested robustly to ensure each staged improvement works symbiotically with the last, avoiding any long term unintended consequences.


PAS 2035 specifies the domestic retrofit process must begin with the assessment performed by the retrofit assessor. This is the foundation of all subsequent retrofit design plans.


The Co-ordinator ensures that all elements of domestic retrofit are properly managed and coordinated, and that a cohesive retrofit plan is designed, tested and implemented.


Designers carry out the retrofit design based on the improvement pathway by the assessor and coordinator. LEAF Designers are qualified Co-ordinators and Architects registered with ARB.


The evaluator oversees the final project and has the skills and knowledge to understand why a project may not have delivered the expected outcomes. The evaluator should be impartial to ensure a transparent view of the project.

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