Which insulation improves your EPC rating most

What an EPC actually measures

An EPC is a modelled estimate of how much energy the building needs, not a measurement of your bills. The assessor records the construction, the insulation they can see or evidence, the heating system and the controls, then the software produces a score.

That distinction matters: the assessor scores what they can see and evidence. Undocumented work often scores as if it were never done.

The measures that move the number most

Roof and loft insulation. Consistently one of the highest-scoring improvements per pound, especially where there is little or nothing there now. Going from 50mm to current depths is a substantial jump.

Wall insulation. Solid uninsulated walls are heavily penalised in the model. Internal insulation on solid walls, or filling a genuine cavity, moves the score significantly.

Room-in-roof insulation. Converted lofts with no insulation at rafter level are one of the worst-scoring elements in the model and one of the biggest gains once treated.

Floor insulation. Smaller effect than roofs and walls, but worthwhile where there is a suspended timber floor over an open void.

Heating controls and lighting also help, but for most Basingstoke houses the fabric — roof first, walls second — is where the score is won.

The order to do it in

1. Loft or roof insulation to current depth
2. Any uninsulated room-in-roof
3. Solid or single-skin walls, worst room first
4. Draughts, hatches, and cold bridges at reveals and lintels
5. Heating controls

Evidence your work

Keep the specification, the product details and photographs of the installation before it was covered. When we insulate we photograph the build-up as standard, and that paperwork is what lets an assessor credit the work — and reassures a buyer's surveyor later.

If you are a landlord

Fabric improvements are the ones that stay improved regardless of how a tenant behaves, and roof insulation is nearly always the cheapest route to a better band. Start there.