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.