3 Disadvantages of Traditional External Wall Insulation

By Jamie Orr
Date 19/04/2022
3 disadvantages of traditional external wall insulation

External wall insulation is a good way to improve a building’s energy efficiency. The traditional choice is some form of cladding or insulation boards. However, it’s important to know the disadvantages of external wall insulation boards, so you can make the right decision for your property. Read on as we take a closer look…

How does external wall insulation work?

While there are other options available (more on that later), the most common way to insulate a wall from the outside is using insulative boards. To be clear, this excludes cavity wall insulation, which isn’t an option for solid walls.

External wall insulation panels are available in a range of materials, including fibre cement and polystyrene. They usually require a layer of render on top for added protection from the elements, as well as to provide a decorative finish.

Disadvantages of external wall insulation boards

1. Impermeability

The biggest potential disadvantage of external wall insulation is that it can cause damp without the right planning. It depends whether your wall is permeable or impermeable.

Permeable walls have been designed to let moisture through so it can be evaporated away, while impermeable walls stop moisture penetrating from both the inside and outside. Buildings with impermeable walls usually have other means of ventilation to stop that moisture building up inside.

However, if a permeable wall is cladded with non-breathable (impermeable) insulation materials, it will let moisture through from the inside, which can’t escape on the outside. That can result in damp walls or insulation, unless a vapour barrier or other means of ventilation is present.

2. Size

Another disadvantage of traditional external wall insulation is the size. Put simply, the boards themselves are pretty bulky. While sizes vary depending on the materials used and the efficacy of the boards, you’re looking at around 50mm being added to the outside of your walls.

The main drawback here is that the walls will no longer fit with your windows, doors or roof eaves. That can leave cold bridges where heat can escape, unless you choose to adjust the fixtures or fill the area around reveals with additional insulation. Needless to say, both will add to the cost of insulating your walls.

3. Cost

External wall insulation doesn’t come cheap. Walls have to be prepared before multiple layers are applied to make sure the insulation works and looks the part. As above, that costly and lengthy process can be made worse if fixtures need to be adjusted.

That’s without mentioning the devastating consequences if your external wall insulation causes damp. In that case, you’d need to fork out for specialist ventilation or have the insulation removed altogether.

An alternative to traditional external wall insulation

Thankfully, there is a way to sidestep the disadvantages of external wall insulation outlined above. CorkSol exterior wall coatings are spray-applied in a thin layer to provide the same insulation without the drawbacks.

The cork-based solution is highly weather resistant, thermally and acoustically efficient, and comes with a guarantee of 25 years. Want to find out more? Contact us today on 01484 442420 or email [email protected].

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