Will loft insulation improve my EPC rating?
Yes, loft insulation improves an EPC rating when the assessor can see it or be shown it. In 2,149 homes in Cambridgeshire and Peterborough where only the loft changed, from 100mm or less to 270mm or more, the rating rose by a typical 8 points and more than half moved up a band. Our free survey tells you what your loft has now.
How much does loft insulation add to an EPC?
No official figure exists. These are from local certificates, each set beside homes where nothing changed.
A typical rise of 8 points, across 2,149 homes where the walls, heating and windows were recorded the same on both certificates.
A typical rise of 4 points, across 2,249 homes. A loft that already has a fair depth has less to gain.
A typical rise of 2 points, across 10,254 homes. Ratings drift a little between certificates anyway, so this is the figure to compare against.
These compare the first and latest certificate for the same home, lodged between 2008 and September 2026. They show what happened in those homes. They are not a promise for yours, because the rating also depends on the size of the house, the heating and the fuel.
Source: our own count from government energy certificate data, explained on how we work out our figures. Read 11 October 2026.Will loft insulation get my EPC from D to C?
It did for more than half of the band D homes in our figures. 57.6% of those that started in D ended in a higher band, against 42.8% of D homes where nothing changed.
Across all 2,149 homes, 58.7% moved up at least one band, against 33.9% of the homes where nothing changed. A home near the top of its band needs fewer points to cross the line than one near the bottom, so the number on your certificate matters as much as the letter. Landlords have a minimum rating to meet. The rules for let homes.
Source: our own count from government energy certificate data, explained on how we work out our figures. Read 11 October 2026.How does an EPC score loft insulation?
By depth. The assessor records how deep the insulation is, and the software turns that depth into a figure for how much heat the roof loses.
The published method gives a figure for each depth, where lower is better. A loft with none scores 2.30. With 100mm it is 0.40. With 270mm it is 0.16. So the first 100mm does the most, and going from 100mm to 270mm still cuts the heat loss figure by more than half. What each depth is worth on paper.
Source: BRE, RdSAP 10 specification, 9 June 2025, Table 16. Read 11 October 2026.Selling or letting? Find out what your loft has.
The survey is free and you get a written price before any work starts.
Why does my EPC say "Increase loft insulation to 270 mm"?
Because the depth on your certificate is low. The method considers that recommendation where the loft is recorded at 150mm or less.
29,189 houses and bungalows in Cambridgeshire and Peterborough carry that line on their most recent certificate. 270mm is the depth the method recommends improving to. Our loft checker shows the rating and the loft depth on yours. How to read the loft line on your EPC.
Sources: BRE, RdSAP 10 specification, Table 33; our own count from government energy certificate data, explained on how we work out our figures. All read 11 October 2026.What if the assessor could not see my loft insulation?
Then the certificate records an assumption, and you may not be getting credit for what is there. 23,058 homes here have a loft recorded as assumed.
- Measured where possible. The assessors' rules say that where safe access is possible, the insulation should be measured and photographed.
- Hidden insulation needs proof. Where it is fully covered, by stored things or by boards, the rules say to record it as unknown unless the householder has documentary evidence or the covering is lifted.
- Seen at the edges counts. Where the assessor can see the insulation at several points under a covered area, the rules say it is treated as insulated to the depth that can be shown.
- Keep the paperwork. Keep the invoice and dated photos of any insulation work, and ask your assessor before the visit what they will accept.
An unseen loft rarely carries the recommendation either. Fewer than 1 in 100 of those 23,058 certificates tell the owner to add loft insulation, so the certificate may say nothing useful about the loft at all.
Sources: Conventions for RdSAP 10, version 12, conventions 3.03 and 3.04; our own count from government energy certificate data, explained on how we work out our figures. All read 11 October 2026.Do I need a new EPC after insulating the loft?
Only if you need the rating to change. A certificate is valid for 10 years, and the rating on it stays the same until a new one is lodged.
That matters when you sell or let, because GOV.UK says you must order a certificate before you market the home. If yours is recent and the loft has been done since, a new assessment is the only way the work shows up.
Source: GOV.UK, energy performance certificates. Read 11 October 2026.Short answers
Does going above 270mm improve an EPC rating?
A little. The method gives 0.16 for 270mm, 0.14 for 300mm and 0.11 for 400mm or more, and it records nothing deeper than that. 270mm or 300mm.
Does a better EPC rating add value to a house?
A government study published in 2013 looked at repeat sales of 325,950 homes and indicated that energy efficiency is a key factor influencing the sale price of most homes in England. The study is on GOV.UK. It is not a figure for loft insulation.
Is the EPC changing?
Certificates for existing homes are produced today with a method called RdSAP 10. When we checked on 11 October 2026, the government planned to launch reformed certificates in the second half of 2027. GOV.UK has the current plan.
How do I find my current EPC rating?
GOV.UK has a free search for any certificate in England. Our loft checker reads the same register and picks out what it says about your loft.
Find out what your loft has
The rating follows what is in the loft. Our survey is free, takes about twenty minutes, and tells you what is there now.
Written by Ben Criddle, who runs Complete Loft Services. Published . Facts checked on .