Common Questions

External wall insulation (EWI) involves installing a layer of insulation material to the outside walls of your house, which can then be covered with render or cladding to give you your desired look. 35% of all heat loss in a typical UK home is through the external walls. Heat will flow to a cooler place. Entire heat loss cannot be stopped but it can be slowed down. This means that less heat will be lost in a given period, so less energy is needed to replace it; less energy equals lower fuel bills. The way to reduce the heat loss is by installing insulation. The most efficient means and least intrusive way of doing so on an existing house is by installing it externally.

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The insulation is installed to the existing wall by sticking it with adhesive and also pinning it with a mechanical fixing. Once this has set we can apply your desired top coat or finish.  

How do the different insulations compare?

Insulation commonly used in EWI include EPS - Expanded Polystyrene insulation , Mineral Wool and Wood Fibre Panels.  There are many ways to compare these insulations but we like to make the 3 main distinctions; Performance, Cost and Sustainability.

Performance - All materials lose heat. The resistance of this loss in a material is known as the R-Value. The higher the R-Value the better its insulating properties or more resistance it has to losing heat. R-values are measured in metres squared Kelvin per Watt (m2K/W).

Need to Know – The R-Value is a good way to compare materials. The higher the number the better an insulator it is. The R-Values of our 3 insulations taken at 100mm thick are:

• EPS - 3.03m2K/W

• Mineral Wool - 2.78m2K/W

• Wood Fibre - 2.40m2K/W

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Cost - The best thing about EWI is that there are options for every budget. The cost of the materials are currently fluctuating more than ever. That being said, a sensible rule of thumb is that Mineral Wool is the most inexpensive option, EPS is mid range and Wood Fibre & other sustainable products are for people who wish to spend more comfortable in the knowledge that their choice has come from a sustainable source. 

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Sustainability - When it comes to sustainability Wood Fibre panels are the most sustainable. Other healthy features include 'breathability' which helps regulate a buildings moisture content. Mineral Wool finishes in a close second with EPS being the less sustainable. That being said, it's hard to disregard the longevity of EPS. It may be made from plastic but once installed it should never perish and will elongate the original lifespan of a home.

Do I need planning permission?

This is taken from The Planning Portal -

Planning permission is not normally required for fitting insulation (where there is no change in external appearance). However, if the building is listed or is in a conservation area you should consult your local planning authority.

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This is sound advice however, consulting your local authority is easier said than done. If you are unsure we can take care of this for you.

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Some real world advice would be: It's always best to speak to the planning department, if you can. It's generally not required where a property is not listed or in a conservation area.  However, there might also be something that triggers planning permission as a consequence of adding EWI.