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What Thickness of Insulation Do I Need For Brickwork?

Installers and homeowners often come to us asking about the optimal thickness of insulation that they will need to achieve the best U-values possible. The lower the U-value of a wall, the better the thermal performance of the building (i.e. heat will transfer through the wall more slowly). External wall insulation can be an expensive project, so ensuring that you get the most out of it with the best energy-saving capabilities possible is essential. In today’s blog we’ll be talking you through the ideal thicknesses for the different insulation materials that we offer as part of our external wall insulation systems.

EPS Insulation

Expanded polystyrene insulation is the most affordable insulation material that you can get for external wall insulation, not only because the actual material is affordable but also because it is so lightweight it only requires lower strength adhesives and plastic fixings – which in turn cost less.

EPS is made from a polymer permeated with a foaming agent which, when exposed to steam, creates a uniform closed-cell structure, highly resistant to heat flow and moisture penetration. EPS is 98% air and only 2% EPS, which means it acts as a fantastic thermal insulator because of its high air content.

When insulating a solid brick wall, 90mm of EPS insulation is required to reach the building regulations u-value of 0.3(w/m2k).

Mineral Wool Insulation

Rockwool insulation offers high levels of breathability due to the fact that it is a vapour-open material. The presence of fibres and water-repelling compounds wick moisture and water vapour through the material away from the substrate, allowing it to escape. Mineral Wool is non-hygroscopic, which basically means that it pushes water away.

Mineral Wool is also a fantastic acoustic and thermal insulator because of the fact that the material is so hard-wearing and the fibres allow for pockets where air becomes trapped and thus acts as an insulator. Due to the fact that it is so durable, this material is guaranteed to be long-lasting.

When insulating a solid brick wall, 110mm of Mineral Wool insulation is required to reach the building regulations u-value of 0.3(w/m2k).

Wood Fibre Insulation

Wood Fibre is our most sustainable, renewable insulation material for use with our EWI systems. All of the timber used for the insulation boards come from waste timber cuttings; in fact, the whole manufacture process is so environmentally friendly that the boards have been certified by the NaturePlus standard.

Known for being very breathable, this material is ideal for externally insulating timber builds, as the two materials work well together in harmony.

The Fire Resistance of Wood Fibre Insulation is rated at Class E, which is very similar to other insulating materials. However, timber tends to char instead of burning. The charred exterior of the board creates a barrier which stops oxygen passing through and feeding the flames, thereby slowing the spread of fire.

When insulating a solid brick wall, 120mm of Wood Fibre insulation is required to reach the building regulations u-value of 0.3(w/m2k).

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