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Thermal Render vs. External Wall Insulation

Our insulation systems are often referred to as ‘thermal render’ or ‘external wall insulation.’ This type of system is made up of physical insulation boards, such as EPS, which are secured to the external wall with adhesive and mechanical fixings, before render is applied on top to achieve a decorative finish.

Thermal render, on the other hand, is an actual render product with low thermal conductivity. This is often specified on the package, for example, our Lightweight Basecoat has a thermal conductivity value of 0.47(W/mK). This essentially means that the basecoat itself will help to slow down the rate of heat transfer. This means that less of the heat from inside your home will be able to escape.

Advantages of External Wall Insulation

If you’re looking to gain thermal performance out of your renovation project, then we really recommend installing external wall insulation. The main advantage of choosing this over a thermal render is that the external wall insulation boards come in a range of thicknesses, so the potential for performance is much greater.

Choosing external wall insulation also means that you get a choice in the type of insulation boards that you go for. We offer EPS, Kingspan K5, Mineral Wool or Wood Fibre, all of which offer different levels of thermal conductivity and therefore have different insulating capabilities.

The insulation material itself can also provide other benefits. Our Mineral Wool insulation comes from Rockwool and has acoustic insulating capabilities as well as excellent fire performance (it’s rated as Euroclass A1 noncombustible).

In terms of comparing this against a thermal render, you’re getting advanced thermal performance, the choice of how much insulation you install, and you can choose a material that will provide your home with other advantages. The thermal render on its own will offer the slightest of insulating benefits, but really it needs to be used in conjunction with a cavity wall insulation or internal wall insulation to see any real effect.

How is Thermal Render Installed?

We do however understand that thermal render is a significantly cheaper option than external wall insulation. If you already have cavity wall insulation then you may decide to just go ahead with the thermal render. There are a few of these products on the market, one of them being our Lightweight Basecoat.

The good thing about the Lightweight Basecoat is that it can be installed up to 50mm thick in two passes. You would embed a fibreglass mesh within the first pass, leave it to dry out a little and then apply the second pass. Once this has set completely, you can then apply a thin coat render or a Silicone Paint on top to achieve a decorative finish.

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