What happens during a retrofit assessment?

A retrofit assessment is the starting point for most well-planned retrofit projects. It records what the home is like now – how it is built, its condition, how it is heated and ventilated, and how it is used – so that improvements can be chosen and designed on evidence rather than assumptions.

Why the assessment comes first

Energy improvements interact. Insulating a wall changes how moisture moves through it. Reducing draughts changes how much ventilation the home needs. A better-insulated home needs a smaller heating system. Without a reliable picture of the starting point, it is easy to choose measures in the wrong order, or to solve one problem and create another.

Where a project follows PAS 2035:2023 – the current British Standard framework for domestic retrofit – the assessment is the first formal stage, carried out by a retrofit assessor. PAS 2035 is required for some funding schemes, including ECO4 and Warm Homes: Local Grant, and for work lodged through TrustMark. For privately funded projects it is optional, but the same structured approach is still helpful.

Before the visit

• Access. The assessor will usually need to see every main room, the loft (where it is safe to enter), the boiler or heat source and the hot water cylinder if there is one.
• Documents. Any existing EPC, drawings, previous surveys, guarantees for past insulation work and planning history are useful.
• Status. If you know the building is listed or in a conservation area, say so in advance.
• Questions. Make a note of problems you have noticed – cold rooms, condensation, mould, draughts or overheating.

During the visit

The assessor works through the house systematically. Typical activities include:

• Measuring rooms, ceiling heights, windows and doors
• Recording wall, roof and floor construction as far as it can be seen without opening up
• Noting the heating system, controls, hot water and any renewable technology
• Recording existing ventilation – extract fans, trickle vents, chimneys and air bricks
• Looking for signs of damp, condensation, mould or defects relevant to retrofit
• Taking photographs to support the record
• Asking how the household uses the home – heating patterns, occupancy, drying laundry and any comfort problems

Some features cannot be confirmed without intrusive investigation. A good assessment records these as unknowns rather than guessing, and may recommend further investigation before design.

Significance and constraints

For older and protected buildings, the assessment should also identify features that contribute to the building’s character or significance – for example original windows, decorative plasterwork or historic facades. This helps everyone understand early what may need consent, or what should be avoided, before options are developed.

What happens after the visit

The assessor compiles the information into an assessment report and runs an energy assessment using the government’s approved methodology for existing homes. In a PAS 2035 project, the retrofit coordinator then uses the assessment to evaluate improvement options and to prepare a medium-term improvement plan, which sets out a sensible order for measures over time.

How long does it take?

This depends on the size and complexity of the home and its occupancy. A small flat will usually take less time than a large house with extensions and a loft conversion. You will be given an estimate when the visit is booked.

Questions to ask before you commission an assessment

• Who will carry out the visit, and what is their relevant qualification?
• Is the assessment being carried out to PAS 2035, and is that needed for your project?
• What will the report contain, and who will it be shared with?
• Is coordination or design included, or separate?

Sources and further reading