Damp After External Wall Insulation

External wall insulation is a great way to improve the energy efficiency of your home by reducing the rate of heat loss through your walls. The great thing about EWI is that it wraps around the entire exterior of your home, enveloping the heat inside. 

EWI is much less likely to cause damp than other methods of insulating (such as cavity wall insulation) because there are far fewer breaks within the material – EWI is known as a continuous insulation method. 

However, correct installation is key. External wall insulation consists of rigid insulation boards (as opposed to a foam) that are secured to the exterior walls of the building using adhesive and mechanical fixings. The hugely important part here is that there are no gaps between the boards and no areas where water might penetrate. 

Thermal Bridges

In the context of external wall insulation and damp, the reason we talk about avoiding gaps between the boards and breaks within the insulation is because thermal bridging can occur. During installation, any gaps should be filled using a spray foam adhesive which will act as an insulator.

Thermal bridges are essentially places where there is a higher rate of heat transfer than the surrounding materials, which results in an overall reduction in thermal insulation of construction. Thermal bridges are responsible for up to 35% of thermal losses and increased condensation and mould growth.

Take for example an insulation system where gaps have been left between the boards. The temperature within the gap is going to be a lot colder than the surrounding insulation boards, which means that condensation will gather in that area and damp will occur.

Poor Quality Insulation

Damp insulation means ineffective insulation. Not only this, but moisture gathering behind the insulation boards can lead to erosion of the adhesive, which can cause serious damage to the system.  

If you start to notice damp on your internal walls, then this could be a sign that water is getting behind your EWI system. Signs of damp caused by external wall insulation should be an immediate cause for concern, and a professional should be called out to assess the situation promptly. 

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