Cavity wall insulation
Insulating a cavity wall is an investment that will make your house safe, energy-efficient and comfortable. This is beneficial for both your health and the environment. Moreover, cavity wall insulation paves the way for a lower energy bill. In this article, you will find out more about the types of cavity wall insulation and the average cost per square metre.
Other popular articles: Cavity wall insulation cost – cavity wall insulation problems
What is a cavity wall?
Insulating the cavity is a specific form of facade insulation that is only applicable if the building has got cavity walls. A cavity wall consists of two walls with an open space of 1.2 to 2.4 inches in between. This gap is what we call the cavity, which can be filled with insulation material.
Houses that were built before 1920 do not have a cavity. So it is only possible to insulate the facades of these houses by means of other forms of external wall insulation. Houses built between the 1920s and the beginning of the nineties, were provided with an open cavity without insulation.
✓ Read more information on insulating an existing cavity wall.
Are you not sure whether your house has a cavity? You can figure this out by measuring the thickness of the outside wall. If this wall is smaller than 24cm, you definitely do not have a cavity wall. Endoscopic research with a camera can give the final answer. This will be carried out for free if you request a quote. Click here for more information.
Insulate an existing cavity wall: procedure
If your house was built between 1920 and 1975, there is a good chance that you have a cavity wall without insulation. In this case, you can easily have these walls insulated. Cavity wall insulation is applied from the outside by a specialised insulation company. They make little holes into the joints, through which one then sprays the insulation. Upon completion, the holes are neatly sealed in the same colour as the rest of the masonry.
The great advantage of cavity wall insulation lies in the fact that no demolition work or other nuisance is required. The insulation can be put in place in less than just one day, which has a beneficial effect on the price as well. You must assume a term of 2 to 5 years in order to pay back the full investment. In order to be sure of a correct diagnosis and the appropriate insulation material, it is best to request quotes from different insulation companies.
⤳ Request non-binding quotes from specialised insulation companies.
Types of cavity wall insulation
To fill a cavity wall, one uses 4 types of insulation: glass wool, rock wool, EPS beads and foam. Each material has its own price and specific properties.
We are all familiar with glass wool in the shape of insulation rolls. As for cavity insulation, glass wool is used in the shape of flakes. Glass wool is quite cheap, has a high insulation value and is fireproof. The material is fit for cavity wall insulation and it has a good price-performance ratio.
Glass wool with a HR++ label has a better insulation value, although it is also more expensive than glass wool in the category HR+. Supafil is an example of fibreglass insulation that is frequently used for cavity walls.
⤳ Read more on Supafil cavity wall insulation.
Beads are white, silver grey or black polystyrene granules. The quality of the granules varies from HR++ to HR; HR++ beads have the highest insulation value. Most of the EPS beads have lower scores on sound insulation and fire protection than glasswool and rock wool. The same applies to the sealing of cracks.
On the other hand, EPS beads are very eco-friendly and they have moisture-regulating capacities. Thanks to that, there is a lower risk of damp problems.
⤳ Read more on EPS cavity wall insulation.
PUR cavity wall insulation
Spray foam insulation (PUR-foam) has got the HR++ label and achieves high rates especially when it comes to sealing cracks and keeping away damp. Polyurethane foam has a good price-performance ratio and it has the ability to fill even the smallest gap, as opposed to other materials.
The main drawback of polyurethane foam is that it contains unhealthy substances. Moreover, it is difficult to recycle PUR insulation. Related to PUR is UF-foam, but it is of inferior quality as opposed to the other materials.
⤳ Read more on PUR cavity wall insulation.
Rock wool compares well with glass wool. Its insulation value is a little bit lower, but it has soundproofing qualities. The downside of this big advantage is the higher price.
Unfortunately, the price-performance ratio is therefore not as good as the other options. Because of its natural origin, rock wool is also more sensitive to vermin.
Rock wool is a vapour permeable material, which means that damp can circulate freely. There is barely no risk of damp problems.
Price guide: payback period and cost of cavity wall insulation
The cost of cavity wall insulation is determined by the chosen insulation material, the total surface and the thickness of the cavity. The accessibility of the building and the state of the exterior walls may affect the price as well. Note: cracks have to be repaired first. A short summary of the prices for each type of insulation material:
When we consider the different types of cavity wall insulation, we can see that glass wool is the cheapest material. In the following, we will give a brief overview of the prices:
- Glass wool: an average price of £13 – £18 per square metre.
- EPS beads: £18 to £22 per square metre on average.
- Polyurethane foam: £22 to £26 per square metre.
Payback period cavity wall insulation
How fast you can earn back your investment depends on the average energy consumption and the thickness of the cavity. On an annual basis, you will save 9 to 11 m3 gas for every m2 that is insulated. The average payback time varies between 1.5 and 4 years. Keeping in mind that the insulation of existing cavity walls has a price of 850 to 1750 pounds, profits will be significant in the long term. Do you plan to sell the house in the future? This may be very beneficial thanks to a more favourable EPC certificate.
Icing on the cake: you can request grants from your grid manager. Read actual information about grants you can request this year in the following article: “Cavity wall insulation grants”.
Ask for expert advice if you want to insulate the cavity wall
In order to apply cavity insulation, you need professionals who can give advice on the most suitable material for your wall cladding. It is therefore advisable to request quotes and diagnoses from different insulation companies.
In the building sector, it is common practice to request several quotations. It is advisable to do so, as the service cost is determined by the company’s costs of labour and machinery. This can differ from company to company. By comparing well, you can easily save hundreds of pounds.
Insulating cavity walls pays off!
When cavity wall insulation is possible, it is always advisable to do so. Cavity wall insulation creates a more comfortable and enjoyable atmosphere in your house. In addition, you prevent damp- and mould problems, energy consumption will drop and the house will be cooler in the summer.
In the picture below, you can see an example of endoscopic examination. This cavity wall has only been partially filled in the past, since people used to think that air gaps were necessary at the time. With this type of cavity walls, it is also possible to blow in extra insulation.