Retrofit is the process of upgrading existing homes to improve their energy efficiency, reduce carbon emissions and lower energy bills for residents. In the UK, it is one of the most significant policy areas of the coming decade — the government has committed to upgrading millions of homes by 2030, and a growing range of funded schemes are available to support delivery.
Whether you are a housing association planning your first programme, a local authority exploring the Warm Homes Local Grant, or an organisation new to the sector, this guide provides a clear foundation for understanding what retrofit involves and how to get started.
Retrofit refers to improvements made to existing buildings that were not included in the original construction. In the context of domestic energy efficiency, this typically includes measures such as insulation, heat pumps, solar panels, draught proofing, ventilation improvements and smart heating controls.
The goal is to reduce the energy demand of the home (through better fabric performance), meet that reduced demand with cleaner energy sources (through low-carbon heating and renewables), and ensure the home remains healthy and comfortable for its occupants throughout.
The UK has some of the oldest and least energy-efficient housing stock in Europe. Around 29 million homes need to be improved to meet net zero targets by 2050. The majority of these homes already exist and will continue to be occupied — they cannot simply be replaced. Retrofit is therefore not optional; it is the only viable path to decarbonising the housing sector at scale.
Beyond carbon reduction, the benefits are immediate and tangible for residents. A well-retrofitted home is warmer, cheaper to heat, less prone to damp and mould, and healthier to live in. Fuel poverty — which affects millions of households across the UK — is directly reduced by bringing homes up to a higher energy efficiency standard.
The UK government funds retrofit delivery through several schemes, each targeting a different part of the housing market:
All major funded schemes require compliance with PAS2035 — the UK standard that governs the whole-house retrofit process. This means every project must involve a qualified Retrofit Coordinator, a proper whole-house assessment and a structured quality assurance process through to TrustMark lodgement.
PAS2035 divides the retrofit process into four stages:
Key point: Every funded retrofit project must have an accredited Retrofit Coordinator appointed before any assessment or design work begins. Without an RC, a project cannot be TrustMark lodged and funding cannot be claimed.
A typical retrofit project involves multiple parties, each with defined roles under PAS2035. The Retrofit Coordinator sits at the centre, managing the process and taking overall responsibility for compliance. The Retrofit Assessor carries out the pre-works survey. The Retrofit Designer produces the installation specification. PAS2030-certified installers carry out the physical works. The project client — the housing association or local authority — commissions and oversees the programme.
For organisations beginning their retrofit journey, the practical starting point is understanding your stock. What is the current energy performance of your housing? Which properties are the worst performers? What funding streams might you be eligible for? A stock condition and EPC review will answer these questions and give you the data needed to develop a retrofit strategy and prioritise investment.
From there, the key is to build the right team — qualified assessors, an experienced Retrofit Coordinator and PAS2030-certified installers — before applying for funding, not afterwards.
Our accredited team works with housing associations, local authorities and installers across the UK.
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