Insulation is usually the first upgrade homeowners think of when trying to improve their EPC rating — and for good reason. Insulation reduces heat loss, lowers energy bills, and can significantly boost a property’s efficiency.

But here’s the truth most people don’t realise: insulation doesn’t always improve your EPC score, and in some cases, it may not affect the rating at all. Your results depend on the type of insulation, the property’s age, what already exists, and whether documentation is available.

Before spending money on insulation upgrades, it’s important to understand how EPC software actually evaluates your home. For expert help, explore our EPC assessor services:
https://epcrate.co.uk/services-epc-assessors-london/

1. When Insulation WILL Increase Your EPC Rating

Insulation boosts your EPC score only when it meaningfully reduces heat loss. The biggest improvements come from:

✔ Loft / Roof Insulation

Properties lose up to 25% of heat through the roof.
Increasing insulation depth to 270mm or more creates measurable, guaranteed gains.

✔ Cavity Wall Insulation

For homes with unfilled cavity walls, insulation can dramatically improve the EPC rating.

✔ Floor Insulation

Insulating suspended timber floors adds a strong efficiency boost, especially in older homes.

✔ Pipework and Hot Water Tank Insulation

Cylinder jackets and pipe insulation also improve your hot water system efficiency.

To learn more about how EPC assessors evaluate insulation, see our About page:
https://epcrate.co.uk/about-us-epc-company-london/

2. When Insulation Might NOT Improve Your EPC Rating

Many homeowners are surprised to learn that some insulation upgrades have little to no effect on their EPC. This happens when:

✖ Your Property Already Has Enough Insulation

If loft insulation is already around 250–270mm, adding more won’t improve the score.

✖ The EPC Software Uses Assumptions

If insulation cannot be seen or documented, assessors must assume standard defaults.
This can eliminate the expected rating boost.

✖ Your Home Has Solid Walls

Solid wall insulation does improve EPC — but only if:

  • Installed correctly

  • Documented

  • Clearly visible

Costly improvements like internal/external wall insulation don’t always deliver as much EPC gain as homeowners expect.

✖ The Insulation Is Poorly Installed

Gaps, damp insulation, or partial coverage stop EPC software from marking it as “effective.”

✖ Other Areas of the Home Are Weaker

Even if you insulate the loft, a poor boiler or single glazing may overshadow the improvement.

3. The Insulation Upgrade Most Homeowners Overrate

Loft Top-Ups Beyond 270mm

Once loft insulation passes a certain depth, EPC software stops giving extra credit.
So adding an extra layer from 300mm to 400mm makes no difference.

4. Upgrades That Often Improve EPC MORE Than Insulation

If your insulation is already adequate, these upgrades may boost EPC faster:

  • Replacing an old boiler with a condensing model

  • Adding smart heating controls

  • Installing thermostatic radiator valves (TRVs)

  • Switching to low-energy LED lighting

  • Upgrading to double or triple glazing

  • Adding renewable technology such as solar PV

Check EPC pricing and compare upgrade options:
https://epcrate.co.uk/pricing/

5. The Biggest EPC Mistake Homeowners Make: No Documentation

Even if your home is well insulated, your EPC will not improve unless you provide proof such as:

  • Loft insulation certificates

  • Cavity or solid wall insulation reports

  • Installer invoices

  • Photographs taken during installation

Without evidence, assessors must assume the insulation is missing or inadequate.

To ensure your assessor records all improvements accurately, book your EPC assessment early:
https://epcrate.co.uk/booking/

Conclusion

Insulation is one of the most powerful EPC upgrades — but it doesn’t automatically increase your rating. EPC improvement depends on:

  • What insulation already exists

  • Whether installation is visible and documented

  • Other weak areas in the property

  • The type and condition of the insulation

Before investing in upgrades, consult a qualified EPC assessor who can identify exactly where your home is losing points.

Email :info@epcrate.co.uk

Phone:020 34884142