In this blog, we are going to look at how loft and cavity insulation can help change your EPC rating. At a time when the EPC rating is growing evermore important (and no longer just a box-ticking exercise), finding a way to improve the energy rating is really important, especially for landlords. Cavity and loft insulation is easy and cheap to do, and will have a decent effect on the rating, so lets take a closer look and see just how much of an influence it can have.
What is cavity and loft insulation?
Most of you probably know what cavity wall and loft insulation are, but perhaps you don’t know the standard thicknesses you should expect. For loft insulation, the current regulations require 270mm of rock wool insulation, for example.
Insulating cavity walls takes less than a day on most properties, and as long as you have a cavity wall that is suitable to insulate, it will be possible. Typically, polystyrene beads or blown fibreglass are used as the insulation material. The thickness of the cavity dictates the amount of insulation you can install, so the performance from cavity insulation will never be as good as that of solid wall insulation, which has no limit on the thickness you can install.
What difference does loft insulation make?
We took a typical 3 bedroom end-terrace property with no loft insulation and gradually added insulation to find the rating improvement. Now, obviously there will be some differences between properties, but the differences in rating points should give you a good idea of the importance of loft insulation to a home:
| Insulation depth (mm) | Energy rating | Improvement from no Insulation |
| 0mm | E50 | – |
| 50mm | D61 | 11 points |
| 100mm | D63 | 13 points |
| 200mm | D65 | 15 points |
| 270mm | D65 | 15 points |
| 400mm | D66 | 16 points |
As you can see from this table, the first 50mm make a huge difference to the score, but as you add more insulation, the returns depreciate significantly. Given the cost of loft insulation, however, it makes sense just to throw in a lot of it – the savings are still there at 270mm of insulation. Adding more than 270mm is probably not necessary however, as the rewards get very small at this depth.
Loft insulation is one of the cheapest ways to insulate your property, so it really does make sense to do even if you don’t need to bump up your rating. Your tenants will be happier too!
How much difference does cavity wall insulation make?
Now let’s take a closer look at cavity insulation. The depth of insulation is not relevant here as the insulation will just fill whatever gap is present. If we take a typical uninsulated property with a rating of F28 and add insulation to all three external walls, we get to E47. That is an increase of 19 points in this scenario – a big difference that will take the property to a rentable energy rating.
Combing loft and cavity insulation is a powerful combination, often boosting the rating by 25 or 30 points, so if the property hasn’t had these improvements then it is a bit of a no-brainer to do.
Every property is different
We have based these numbers on a semi-detached property, so if you have a detached house you are likely to see even more gains, whilst a flat or a mid terrace is going to benefit less. Every property is different, so don’t rely on these figures for yours. We also understand that some properties just can’t be insulated in this way, either due to an unsuitable wall type, lack of loft space, or planning considerations. This is why we really recommend getting a full recommendations report from us with a site visit. This will help you to understand the problem areas and what would be the most cost-effective way to improve the energy rating up to the required level.
Hi,
Could you tell me if cavity insulation has been done on my house? How do i tell?
Hi bhav,
The easiest way to tell is to look for little spots in the mortar between the bricks. If you see a regular pattern with these little spots then this is where the insulation was injected. If you have a modern home built in the 80s or later, then the insulation may already be built into the house and then the spots will not be visible.
That assumes you have a cavity wall of course. If you have a solid wall you will need to look at EWI or IWI.
Best,
Alan
Hi, our house is cold! We have holes in the outside wall which i have learnt is a sign that we do have cavity wall insulation. But is there a chance the cavity wall insulation has slipped down the walls? Could this be a reason the house is cold? Do people get heat loss camera surveys of properties to show this? If it is possible to see if it has slipped can we pump more insulation in or do we need to remove the insulation that is there and then start again? Sorry lots of questions but thanks in advance for your help!
We had our loft insulated about 10 years ago for free, having been up there it comes just above the joists. 2 questions. Firstly should we add more insulation on top of it? If we were to do this would it dramatically improve the EPC rating? Thanks.
Pleased to come across this useful blog post. Do you happen to know if sellers are obliged by law to tell potential buyers if the house has cavity wall insulation, or at least if they’ve had it put in themselves?
Hi David,
In many instances the sellars simply won’t know. Cavity wall insulation has been retrofitted into walls for the last 40 years and people don’t tend to hold on to houses for that long anymore. If you need specific info then I would get in touch with CIGA who are the industry body for cavity wall insulation (although they get some very negative reviews online!) who might be able to help further.
Hi Mary, thanks for getting in touch. Firstly you can absolutely add more insulation on top of the existing insulation however I think the savings you will benefit from this will be minimal (provided you do indeed have 100mm in there at the minute which is the normal depth of joists. The EPC rating definitely won’t significantly improve if you do add the extra insulation.
Hi Katrina,
You have been doing your research! Yes – it is possible to take a picture of the house with an infrared camera to identify the different rates of heat loss. This is a good way of seeing if the insulation has slipped. You can top it up, but you may want to remove it depending what type of insulation is in the cavity at the minute. Removing cavity wall insulation is very expensive though so topping it up will be much cheaper. It won’t unfortunately impact your EPC rating since the assessor will assume the insulation in the cavity is present!
When measuring the depth of insulation on the floor of the loft, do you include the insulation between the rafters as well as the insulation above them? It would be helpful to know. Many thanks.
My loft space is largely boarded but the roof insulation is visible on the sides. Does not being able to view under the boarding affect the assessor’s report of the insulation in roof?
Thanks
We’ve just bought a terraced house with rating D64. The report said “Roof Pitched, no insulation (assumed) Very poor”. Bizarrely, the advice for improving the EPC grade did *not* include adding loft insulation! However, we have done now insulated the attic with 270mm+ insulation, largely because it’s the right thing to do. The advice on the EPC certificate is to improve wall insulation. We haven’t done this, partly because it is expensive and disruptive to do in this house. Will the grading go up beyond 69 given that we have installed loft insulation where there was assumed to be none? Should we get the house regraded, given this change?
Is recycled wool good enough for increasing the EPC rating ie if 400mls are put in, will this be the equivalent of 270mls??
My 5 bedroom house has just had an EPC inspection. The house is 50 years old and has had wall insulation double glazing.and loft insulation. The loft also has tongue and grove wooden boards throughout the roof space. Unfortunately the Assessor could not see the insulation and I did not have any paperwork. The insulation was carried out by my late husband. I understand EPC inspections are calculated on what is seen and complicated measurements.
It seems I would have to incur expensive recommended solar panels and electric heat installation to change a proposed rating of G to a lower rating.
I am at a loss regarding the reasoning of not been able to see loft insulation and the visible evidence of better insulation with a wooden floor covering in the entire roof area.
I recently had an epc survey completed. The rating given was D67. When I bought the house 12 ears ago it was rated D61.. However in those intervening years I have fitted loft unsulation (the minimum recommended) and cavity wall insulation….. so how can the rating have increased by only 6 points? I am mystified.
Can I get it reassessed by someone else.?
Hi, I wonder if you could advise. I live in a rented Victorian house, refurbished in 2000. On my EPC from 2014 it says ‘Wall – solid brick with internal insulation’. The EPC surveyor who came last week said he needs evidence that the wall is insulated ie he wants to see some sort of building specification from 2000. Since I don’t have this, and it’s important for me to reach Energy Rating C, I don’t know what to do for evidence. My husband drilled some boreholes to show the insulation but the surveyor wouldn’t accept them as evidence. My landlord is threatening to sell the house, where I’ve lived for 40 years if the rating is below C (it’s currently D).
Can you suggest a way of getting evidence please? I would be very grateful.
Jane
I know of only one domestic property other than >this< with a rating under G15. And that is one with single glazing, solid walls, quite large, and selling with planning permission to be demolished and totally rebuilt…(To be sold at auction. Lake District – nice dooer upper)
So in your professional opinion and experience, just how bad would a domestic property have to be, to score an incredible G1. That is one. A total points score of ONE. Just making that clear 😉
Double glazed. One wall internal insulation with 100mm rockwool. Low energy light bulbs throughout. 2 walls are party walls. 200mm rockwool in roof space.
The 'surveyor' refused to accept anything. Even though both internal wall and roof space was in fact accessible to examine, he chose to ignore them.
No heating – "electric assumed" – true, it's so toasty I don't need space heating.
Immersion heater observed to be insulated with 150mm rockwool, but still was zero rated.
Does a score of just one sound right?
Are there any domestic properties anywhere else in the UK with a score of just one?
Was this surveyor having a giraffe?