London & South-East England
Whole House Retrofit
Fabric first, in the right order, planned by our own PAS 2035 retrofit coordinator and assessor.
Is whole house retrofit right for your home?
- Owners of a solid wall house planning insulation, a heat pump and solar who want them in the right order
- Anyone who has had one measure go wrong (damp after cavity fill, a cold room after IWI) and wants the whole picture
- Buyers of a Victorian, Edwardian or 1930s house planning a full renovation
- Households working to a multi-year budget who want a plan rather than a series of separate quotes
- Landlords and owners of flats and maisonettes who need a documented, lodged retrofit
Whole House Retrofit: key facts
- PAS 2035 is the UK framework for whole house retrofit: assessment, a medium term improvement plan, coordination of the work and evaluation at the end.
- Order matters: fabric first (walls, roof, floor), ventilation with it, then heating and generation.
- Retrofit assessment typically £300 to £600; coordination typically 5 to 10% of the works; whole house packages £15,000 to £60,000 depending on the measures.
- Insulation installed by our own PAS 2030:2023 certified team; heat pumps, solar and windows by accredited MCS, FENSA or CERTASS certified partners.
- The plan can be phased over several years, so you do the right work in the right order as budget allows.
- Insulation, solar, batteries and heat pumps are 0% VAT until 31 March 2027; windows and electrical work are 20%.
What is whole house retrofit?
A whole house retrofit treats the house as one system rather than a list of unrelated jobs. PAS 2035 is the British standard framework for doing this properly. A retrofit assessor surveys the building, its condition, its ventilation and how the occupants use it. A retrofit coordinator turns that into a medium term improvement plan that sets out every measure, the order to do them in and the risks to manage. The work is then installed to PAS 2030, and the coordinator checks and evaluates it at the end.
The order matters because each measure changes how the house behaves. Insulate the walls and roof first and the heat demand falls, so any heat pump fitted later can be smaller and run at a lower flow temperature. Add ventilation with the insulation and the moisture that used to leave through draughts has somewhere to go. Do it the other way round, a heat pump sized for a leaky house or insulation with no ventilation, and you get an oversized system, condensation in the corners and cold bridging where one measure stops and the next begins. Most of the problems people blame on insulation come from piecemeal work.
Stay Warm has its own PAS 2035 retrofit coordinator and retrofit assessor on the team, which is unusual for an installer. They produce the assessment and the plan; our own PAS 2030:2023 certified team installs the insulation; accredited MCS, FENSA or CERTASS certified partners fit the heat pump, solar or windows. You deal with one project manager throughout, and the plan can be phased over several years so the work is done in the right order as your budget allows.
Who does the work
Stay Warm's own PAS 2035 retrofit coordinator and retrofit assessor plan the work. The insulation is installed by our own PAS 2030:2023 certified team. Heat pumps, solar and windows are arranged and project-managed by Stay Warm and installed by accredited, certified installers (MCS for heat pumps and solar, FENSA or CERTASS for windows). One plan, one project manager.
Whole House Retrofit cost guide
Indicative 2026 market ranges for London and the South-East. Every package is different; the assessment and plan come first and the works are then quoted measure by measure.
| Job type | Indicative cost |
|---|---|
| PAS 2035 retrofit assessment | £300 – £600 |
| Retrofit coordination | 5 – 10% of works |
| Fabric package (walls, roof, floor, ventilation) | £15,000 – £35,000 |
| Heating and generation (heat pump, solar, battery) | £10,000 – £25,000 |
| Whole house package | £15,000 – £60,000 |
VAT: mixed. Insulation, draught proofing, solar, batteries and heat pumps are 0% VAT until 31 March 2027 (HMRC VAT Notice 708/6); windows, ventilation and electrical work are 20%; assessment and coordination fees are standard rated, and the quote shows each line.
What a PAS 2035 retrofit includes
How a whole house retrofit works
Free survey, then assessment
A free heat loss survey first. If you want to go ahead, our retrofit assessor carries out the PAS 2035 assessment and writes the report.
The improvement plan
Our retrofit coordinator sets out every measure in order, with costs, the ventilation strategy and what can be phased into later years.
Installation in sequence
Fabric first by our own team, then heating and generation by certified partners, with the coordinator inspecting at each stage.
Evaluation and handover
The coordinator checks the finished work against the plan. You receive the guarantees, certificates and the lodged record for each measure.
Free survey & fixed quote
Book a free, no-obligation survey and we will send a clear, fixed written quote. One point of contact from survey to sign-off, and a written guarantee on the work.
Get a free quoteWhole House Retrofit FAQs
What is PAS 2035?
Why does the order of work matter?
What does the retrofit assessment contain?
Can it be phased over several years?
What does a whole house retrofit cost?
What does the coordinator do for me?
Areas we cover
We arrange whole house retrofit across Greater London, Surrey, Kent and Hertfordshire. See all areas we cover →
Related guides
In-depth, independent guidance to help you decide.
Last reviewed September 2026 by Stay Warm Insulation.
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