Exterior wall insulation is also known as external insulation. This is used to insulate the main walls of your house from the outside.
Most homes in the UK built before 1925 – 1920 will have solid walls.
This makes it much more difficult to insulate walls, since there isn’t a cavity where you can put blow in insulation.
Although it is more challenging, it doesn’t necessarily mean that it’s impossible. When it comes to insulation of your walls, you still have two options:
Internal wall insulation – This type of insulation is applied to your main exterior walls.
Exterior wall insulation- This is a fairly obvious place, but insulation is applied to exterior walls.
This article is about external wall insulation. We’ll discuss why you might choose it over interior insulation, and the main benefits and disadvantages.
How do you determine if you have cavity walls or solid walls?
As we mentioned, if your house was built prior to 1920-1925 in the UK, then it most likely has solid walls.
Visually, the best way to determine this is by looking at un-rendered brick walls. If you can see both the sides and the ends of the bricks then it’s a solid wall.
You will need to measure the thickness of your external walls if they are rendered. This can be done most easily through a doorway or window opening. You will probably have solid walls if it is between 230-250mm and 300mm or more.
Also, don’t assume your walls will be the same. My house has 250mm solid brick walls as well as 600m solid rock walls.
Head on over to PD Rendering & External Wall Insulation for more info on EWI.
What are the reasons you might need exterior wall insulation?
Here are the main reasons why exterior wall insulation is recommended:
Your home’s walls do not have a cavity that you can insulate. In older homes, this is common.
You don’t want your floor space to be lost by insuring internally. To do this, you would have to insulate to the inner side of the main exterior walls. This usually involves building a timber frame and installing rigid insulation. A vapour barrier is then added and plasterboard finished.
This could mean you lose anywhere from 100 to 150mm of floor space, depending on which insulation you use and what u-value you select. You’ll also lose the space if there are more than two walls.
It might not matter if you have large spaces, but it could be a problem if you have very small rooms.
You want to reduce cold bridging. This is when cold gets transferred from the outside into your home. Masonry is a good conductor heat, so the cold moves quickly through the wall.
Cavities were made to reduce this problem because the cold cannot get through the cavity. Air and insulation are poorer heat conductors than brickwork.
Cold bridges can also exist in cavities properties. As cold bridges between cavities and sills (e.g. at window head or sills), the cold can get through to the inner walls.
External insulation minimizes the possibility of cold bridging. It wraps the house in one big sheet of insulation, which separates the cold air and masonry walls.
Some cold bridges can be maintained at wall junctions, etc., despite the fact that internal insulation is still available.
You can use the thermal mass of main walls to your advantage (almost as a storage heater). Alternatively, you could insulate the main walls internally to keep heat inside. The masonry walls are never warm.
If you insulate the walls externally, the large thermal mass and heat of masonry walls will slowly heat up. The walls gradually release stored heat after you turn off your heating. There is insulation on the exterior of the wall so that most of the heat goes back into the house.
You wish to renew/renew the exterior appearance of your property while increasing its thermal efficiency. This is possible due to exterior wall insulation. Your home will look new again with a freshly rendered brick slip finish.
The exterior wall insulation is applied chemically and mechanically to your walls. This applies only if they are in good order. The exterior walls are usually finished in acrylic or rendered finishes.
These finishes can come with colour pigments mixed in, so that you don’t need paint the exterior. This alone could save you thousands of dollars in future decorating costs.
The advantages of exterior wall insulation
These are the main benefits of exterior wall insulation. I have already covered them in detail so I’ll just repeat them here.
Avoid cold bridging
It won’t result in you losing valuable floor space.
Let’s see if the thermal mass in the walls can be used as a heat sync.
Your home will be a new place from the outside.
It can help reduce future redecoration cost.
It dramatically increases your home’s thermal efficiency.
External wall insulation’s disadvantages
External insulation is more expensive than internal insulation (last quote was around PS100/m2). This will typically cost twice as much to insulate internally. However it will usually be twice as costly as internal insulation. Additional costs may include moving radiator pipes away form the walls, replacing flooring, and relocating fireplaces from the walls.
You should consider several factors when deciding whether exterior wall insulation will work for you.
Is it a priority to maintain internal floor area?
It is possible to afford it.
Is it possible to improve the exterior of your home, and lower future redecoration expenses? Alternately, if you are planning to redecorate your house internally, insulating internally may be a good idea.
I think exterior wall insulation has more advantages than interior insulation. There is one drawback (and that’s a biggie), and it’s cost.
The cost of insulation internally can easily be surpassed by external insulation, even if your home is in good condition.
If cost is what’s stopping you from getting your project done, speak to your installers. They will be able inform you if any grant assistance is available for your area.