Cavity walls exist in properties that do not have solid walls, and usually date after
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There are a few ways you can insulate your home’s walls and the type of insulation you use will largely be determined by the construction of your walls, largely whether you have solid walls or cavity walls. External insulation is one of the most common types of thermal barrier insulation for older solid brick wall properties, typically ones built before the 1920s that aren’t suitable for cavity wall insulation.
Find out more about exterior wall insulation, the advantages and disadvantages, and how much you might expect to pay for installing it.
The first thing to establish is whether external insulation is suitable for your property, or whether you’ll have to consider installing another type of insulation such as cavity wall insulation. To do this, let’s dive into the difference between cavity walls and solid walls and the options when it comes to insulating them.
A cavity wall is a wall made with two layers with a cavity (hollow space) in the middle of them. Cavity walls were introduced in the 1920s to help with ventilation, so if your house was built in the last 100 years, you’ll likely have these types of walls.
A solid wall doesn’t have a cavity inside it; it’s simply one solid wall. Houses built before the 1920s tend to have solid brick or stone walls. If you’re not sure whether your walls have cavities or are solid walls, you can check the brickwork. If the brick wall is even and all the bricks are a similar length, you likely have cavity walls. If you’re unsure either way, call in a professional who can give you more information.
If you have solid walls, there’s no cavity to fill with insulating material, so cavity wall insulation is not an option, and you’ll instead have to insulate either the outside or internal walls. We’ll be exploring the former option – external insulation.
If you want to improve your home’s thermal efficiency, installing solid wall insulation is an excellent option. You can expect significant reductions in your energy bills and a smaller carbon footprint.
With solid wall properties, there’s no option to install insulation into interior cavities, since no cavities exist. Instead, you have to add insulation either to the inside or the outside of the walls – known as internal wall insulation or external insulation.
When it comes to external insulation, a considerable advantage is that you don’t have to take up space inside your home. Internal wall insulation, on the other hand, reduces the space in your home’s interior. You’ll pay significantly more for the benefits associated with exterior wall insulation or solid wall insulation systems, though, so consider your budget before committing.
Like every insulation material, there are advantages and disadvantages to installing external wall insulation. Let’s explore some of the main ones.
This type of insulation comprises polystyrene balls packed tightly together to make a board. EPS is cheap, light, and easy to work with. The trapped air bubbles in the material prevent heat from transferring from one side of the board to the other.
One of the main disadvantages of this material is its poor fire rating. When the EPS is integrated into a fully covered system, this shouldn’t matter too much, as the fire should come into contact with the render before making it into the insulation. It’s worth considering, though, if fire safety is a key concern.
Mineral wool is also a common material in loft insulation systems. When used for external walls, the mineral wool is further compressed into a rigid board. The benefit of this type of insulation is that, unlike EPS, it has a high fire resistance rating. It’s great for soundproofing, too. On the other hand, the heaviness of the material makes it more difficult to work with, which can increase labour costs.
Wood fibre is the most sustainable option for your home as it can be made from recycled materials, typically from the sawmill industry. This material tends to come in boards or quilts and also offers excellent thermal efficiency. The biggest disadvantage of wood fibre is its high cost compared to other external wall insulation materials.
While it’s tempting to try your hand at an external wall insulation DIY project, this type of insulation isn’t suitable for installation by anybody other than a professional, unless you have previous experience with projects just like this one.
Instead, search online for a qualified professional installer with previous experience of solid brick wall insulation installations and the reviews to show for it.
Whichever type of insulation you opt for – whether it’s inside insulation, external insulation, or loft insulation – you shouldn’t go ahead if damp and condensation are present in the area.
There’s a complicated relationship between external wall insulation and damp that should be considered before going ahead with insulation. Before cavity walls were introduced, solid brick walls tended to be impermeable walls that stop moisture penetration. Many insulation materials are non-permeable and clad to prevent rainwater penetration.
They can’t, however, prevent moisture from the inside of the home from reaching the wall, so more ventilation is needed to remove moisture from the air before it reaches the walls.
The air’s dew point is the point at which air meets a temperature that causes the moisture to condense into water. The temperature through a wall changes as the air moves from the external temperature to the internal temperature.
If the wall doesn’t have a ventilated cavity, the dew point should occur on the external surface. Adding insulation, however, can change the dew point of the air that enters through your wall.
External insulation heats your wall, which moves the dew point towards the cooler, external air, reducing the risk of condensation. Unfortunately, in some cases, the dew point occurs between the insulation and the wall or in the insulation itself, causing condensation.
When left unchecked, condensation can lead to long-term issues such as damp and mould. To avoid this happening, install a vapour barrier between the wall and the insulation. Ask your supplier for more information.
No matter how you install external wall insulation, the simple fact is it will change the external appearance of your property. In many cases, that change requires planning permission from your local authority.
This is especially important if your property is a listed building or within a conservation area, and in this case, your local council might refuse to give consent.
There are no two ways about it; external insulation isn’t cheap. If you’re working to a tight budget, however, and want to save some money on typical installation costs, here are some tips.
If exterior wall insulation isn’t financially feasible for you, but you want the benefits that come with installing insulation, try a different type, such as loft insulation. Loft insulation tends to be cheaper and will also help to keep your home cooler in the same, warmer in the winter, and more environmentally friendly all year round.
If you have solid walls in your home and you’re looking for a way to save costs and the planet at the same time, external wall insulation offers an excellent solution. There are, however, some things to consider before you go ahead.
If you work with the right professional, they’ll be able to let you know whether your home is suitable for external wall insulation and whether it’s likely to cause any problems with damp, for example.
Remember to ask whether you need planning permission from your local authority before starting a project. Failing to do so can have costly consequences, especially if you live in a listed property.
If you’ve decided to go ahead with wall insulation, we can help by introducing you to trusted installers who can advise you on the best wall insulation option for your home and then provide you with a highly competitive quote. By using our recommended insulation installers will provide you with full peace of mind that the insulation job you have done will be completed to the highest standards, providing you with energy bill savings for many years to come.
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