Is External Wall Insulation Worth It?

Insulating an external wall

Ever feel that chill creeping into your home on a cold morning? Somehow, the chilly air manages to find its way into your home, even if you crank up the heating all the way. 

The easiest method to resolve this issue is by installing or improving the insulation in your walls. However, some homes in the UK have solid walls that don’t come with convenient gaps or cavities that can be filled with cavity wall insulation. 

In that case, one of your available options is external wall insulation. This allows you to insulate your property by fixing a thermally efficient material to the outside of it. 

If that sounds intriguing, you’ve come to the right place. From the benefits and drawbacks to the cost considerations, we’ll cover it all. Plus, we’ll help you answer the question on everyone’s mind — is external wall insulation worth it?

What Is External Wall Insulation and How Does It Work?

In the UK today, modern construction practices mainly feature homes built with cavity walls. It’s a legal requirement mandated to ensure the safety and thermal efficiency of houses in the country. 

However, this wasn’t always the architectural norm. Before the 1930s, particularly during the Victorian and Georgian periods, homes were often constructed without these wall cavities. 

At the time, UK houses featured solid brick walls, lacking the essential gap in contemporary constructions. While these walls were incredibly sturdy and durable, they came with their own set of issues. 

For instance, the solid nature of the structures means that you can’t install insulation easily. That’s when external wall insulation (EWI) came into play. 

EWI serves as a tailored solution designed specifically for homes with solid walls. Instead of filling the gap inside walls, this method involves fixing an insulating material to the outside of the structures.

That should reduce the thermal conductivity of your walls, which will help you keep cold air outside your house. So, your home will stay warm, without running up your energy bill. 

How Does External Wall Insulation Impact U-Value?

To help you understand how useful external wall insulation can be, we have to take a look at its thermal transmittance, or U-value. This is the rate of transfer of heat through matter.

It allows us to measure a material’s ability to conduct thermal energy. As a general rule, the lower the U-value, the more insulated your home will be. 

On average, a home with a solid brick wall around 225 mm thick will have a U-value of about 1.2 W/m2K. This is a relatively high figure when you consider that the requirement under Building Regulations is to reduce that to no more than 0.3 W/m2K.

That’s why EWI is crucial. It can significantly reduce the U-value at a reasonable cost.  

What Are the Benefits of External Wall Insulation?

Now that you know what EWI is and how it can help you, we can move on to the benefits of this type of insulation. So, join us as we list some of the chief advantages of installing EWI. 

Right off the bat, EWI will reduce heat loss from the inside of your home, which should help you keep your energy costs low. 

Besides that, this type of insulation won’t affect the internal floor area of your house. Since it covers the outside of your property, the inside should remain unchanged. 

This also means that EWI won’t disrupt the house while being installed. You can carry on with your normal routine while the construction workers put the insulation in place. 

Plus, EWI can increase the lifespan of your walls. The material will act as a protective layer, keeping your walls away from the elements that can cause wear and tear. 

Finally, not only will this type of insulation improve weatherproofing, but it’ll also enhance the sound resistance of your walls. For that reason, if you live in a particularly noisy area, EWI may be the perfect solution. 

What Are the Drawbacks of External Wall Insulation?

Even though EWI can provide your home with countless benefits, this insulation type does have its fair share of drawbacks. 

For example, it has the potential to cause issues with condensation. If the installation isn’t perfect, water droplets can collect between the insulation and your walls. This can cause major problems and lead to your walls degrading.

Moving on, you may have to install a relatively thick layer of EWI to reduce the U-value of your home to an acceptable figure. Sadly, that can cause issues around windows, sills, and eaves. 

Other than that, some properties in Conservation Areas won’t permit individuals to install EWI. That’s because the installation will alter the exterior appearance of your home. 

Last, but certainly not least, EWI can cost a serious amount. The installation process can be exceptionally pricey, depending on the size of your property and its location. 

How Expensive Is External Wall Insulation?

We mentioned that installing EWI can be expensive, but without exact figures, it can be tough to decide if the process is worth it. 

Normally, it can cost anywhere between £100 and £250 per square metre of EWI. This will include the value of the insulation material and the installation process. 

In contrast, the average cavity wall insulation only costs around £35 per square metre. 

That may seem like a massive difference, but that’s because there are a few factors that’ll impact the final price of your EWI. 

First up, we’ll have to take the location of your property into account. If you live in a high-rise flat, construction workers will need to set up scaffolding and other heavy-duty equipment to reach the exterior of your home. 

Besides that, the layout of your house can impact the total cost. Moving on, depending on where you live, you may need to file for permits to install external wall insulation. This process will require you to submit documentation about your property, which can be time-consuming and expensive. 

Finally, the type of external wall insulation you install will come into play. For instance, foam panels tend to be more expensive to install than fibreglass insulation

Will External Wall Insulation Impact the Value of Your Home?

One of the main long-term benefits of installing EWI is that it can enhance the resale value of your home. Since the insulation will improve the thermal efficiency of your house and its external appearance, chances are your property value will also increase. 

Yet, this will depend on the type of external wall insulation you install. That’s because some varieties, like cork insulation, are exceptionally durable and breathable. 

This means they won’t face any of the dampness issues we discussed earlier. For that reason, this type will significantly improve the value of your home.

On the other hand, a few EWI varieties, like foam panels, tend to be thicker and will degrade faster. Because of that, these won’t have a major impact on the resale price of your property. 

Wrapping Up – Is External Wall Insulation Worth It?

If you’re wondering whether external wall insulation is worth it, without a doubt, the answer is a resounding yes. EWI can improve the thermal efficiency of your home, which means the interior will stay warm for longer. 

Not only will this create a comfortable living environment, but it’ll also help you keep your energy bills low. Lastly, installing EWI can even improve the resale value of your home.

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