Wall Insulation

Wall Insulation: Buyer's guide

According to the UK government's statistics, there are more than 6 million houses in the UK that have installed cavity wall insulation. That's a significant number of households enjoying some sort of saving on their heating bills.

With that in mind, we would always argue that insulating your walls makes sense. It makes your home more comfortable, increase the lifespan of your walls and reduce your carbon print. And you will feel it in your wallet as well, as on average you could save up to £30 per month.

The rate at which you will recoup your investment depends on where you install the insulation (internal or external walls), what types of walls you have (solid or cavity walls) and the type of insulation material you choose.

But the benefits to your quality of life will be felt straight away. Your home will be more resilient to changes in temperature and more energy efficient.

There are many types of insulation products used on walls. For instance, in a house under construction, it is not uncommon to use Fiberglass wall insulation roll, on all sides of a finished wall.

But first, you need to determine what type of walls are in your home. In most cases, you will find either cavity walls or solid walls.

External Wall Insulation

External wall insulation is one of the best ways to protect your home against damp and penetrating moisture. This not only slows down the movement of heat through the walls but also offers greater protection to your walls against rain penetration and frost damage.

In most cases, mineral wool insulation or expanded polystyrene slabs are fixed to the wall, before being rendered to make it weather resistant.

While more expensive than internal insulation, it is very effective and should not be overlooked. Plus you can lower the cost of other major works are carried on at the same time.

Apart from the obvious energy saving, the benefits are multiple:

• No loss of floor area and no disruption inside the house
• Less chance of draughts and condensation on internal walls
• Weather-proof and sound barrier
• Better “life expectancy” for the walls

Cavity Wall Insulation

Cavity wall is basically an inner block wall and a brick wall separated by a cavity. To insulate a cavity wall, it is just a matter of drilling small holes on the outer wall to inject the insulation and fill the gap before sealing the holes. It’s a quick and easy job to do.

Internal Wall Insulation

Internal walls are areas that need insulation too. Most people choose to install rigid boards to the walls along with a vapour barrier and plasterboards. This process is also known as drylining.

In the UK, most homeowners tend to avoid insulating interior walls – which goes against every insulation theory dropped on this planet since 1867. Insulating interior walls can provide you with some sort of soundproofing facility and money-saving on energy bills.

Obviously, it is best to insulate your internal walls during the construction phase for economical reasons. However, should you forget about it, you can always insulate your home’s existing walls at a later stage. But be very careful to avoid tearing off your drywall.

How to find out if your walls are insulated

The best way to check if your interior walls are insulated is to touch them. If you don't feel any warmth or dryness, or if you recoil slightly and feel the need to wipe your hands on your trousers, then your walls are probably not insulated as they should be.

On the other hand, insulated exterior walls should feel cold as the heat is retained inside the house. Take note of the thickness of the walls to determine if its a cavity or solid wall.

Any signs of mould or dampness are a dead giveaway.

How to insulate a solid wall

Solid wall insulation is not an easy task. Some people do it themselves, but unless you have experience with wall insulation, you should hire professionals to do the work.

For internal walls, rigid foam boards from brands such as Celotex or Kingspan are often used because of their excellent thermal properties and their thinness.

For external walls, you first need to fix a layer of insulation material to the wall. The next step is to cover it with cladding or cement.

If your home has solid walls, you can insulate either outside or inside. You won’t lose space if you choose to insulate from outside but the overall cost will be higher. Again, installing or adding insulation to the external walls is usually not a DIY project.

Here’s a quick video explainer on insulating stud walls:

Is it worth insulating exterior walls?

External wall insulation is one of the best ways to protect your home against damp and penetrating moisture. This not only slows down the movement of heat through the walls but also offers greater protection to your walls.

While more expensive than internal insulation, it is very effective and should not be overlooked. Plus you can lower the cost if other major works are carried on at the same time.

Apart from the obvious energy saving, the benefits are multiple:

• No loss of floor area and no disruption inside the house
• Less chance of draughts and condensation on internal walls
• Weather-proof and sound barrier
• Better “life expectancy” for the walls

How thick should wall insulation be?

When you install insulation on your external walls, it is important to ensure that it adheres to the building regulations of the UK. Here, we are talking about the insulation’s thermal performance. Your external wall insulation needs to achieve a U-value of 0.30 watts/m2k.

The appropriate thickness will depend on which the insulation material you pick.

To make things easier you usually have either EPS (Expanded Polystyrene) at 90mm, Mineral wool at 110mm or PIR at 70mm on external walls.

For the internal wall, the thickness depends on the insulation material, for example, rigid plasterboards can be 60mm to 110mm thick, whereas mineral insulation should be 120mm.

Make sure you use a thicker material for better performance. For instance, with expanded polystyrene, you need to use at least 90mm of insulation.

Should you insulate interior walls?

Wall, both interior and exterior, are areas that need insulation. For exterior walls, most people choose to install rigid boards along with a vapour barrier. On the other hand, cellulose, foam, and/or fibreglass batts are mostly used for interior walls.

In the UK, most homeowners tend to avoid insulating interior walls – which goes against every insulation theory dropped on this planet since 1867. Insulating interior walls can provide you with some sort of soundproofing facility and money-saving on energy bills.

Obviously, it is best to insulate your internal walls during the construction phase for economical reasons. However, should you forget about it, you can always insulate your home’s existing walls at a later stage. But be very careful to avoid tearing off your drywall.

What is the cost of insulating existing walls?

Typically the cost for internal wall is around £40 to £50 per square meter, this figure can go higher if you need to build a stud wall. For external walls, the overall cost is between £5000 to £18000 depending on the size of the house. Remember this is not a DIY job unless this is your line of work. Which is unlikely if you are reading these final lines.

In conclusion, if you want to know more about what solution or products you need, our customer service would be happy to point you in the right direction. From Wall Insulation boards, wall insulation Sheets, solid wall, insulation sheets and everything in between, we have a comprehensive range of wall insulation materials to meet your specific needs.