Everybody agrees that insulation is the key component of an energy-efficient home. But what sort of insulation? And how much to use?

It’s here that things get a little tricky, because the world of insulation is filled with lots of different products, many of them with competing claims. Synthetic or natural? Plastic or fibrous? Sheet material, woolly blankets or sprayed in? The best way to look at it is on an application basis.

Cavity Walls

Mineral wool batts are number one here because they are cheap and easy to install. The batts are designed for conventional brick and block walls and are available at thicknesses of 100mm, which is enough to satisfy current Building Regulations, and can be easily doubled up. In wetter locations, a part-fill cavity solution is often required, and the usual material is polyisocyanurate boards (such as Celotex or Kingspan), which can be pinned against the inner skin and still leave a clear cavity against the outer face. Alternatives include retro-filling the cavity after the wall is complete — the same option as cavity fill on existing homes.

Non-Cavity Walls

In timber frames, the most common insulation is mineral wool, supplied as semirigid batts which are wedged in between the studs. Plastic board insulation can also be used and there are a number of spray-in solutions as well. Alternatively, insulation can be wrapped around the exterior of the wall. There is also an uptake of natural insulation materials here (SEE BELOW).

Insulated Wall Systems

An increasing number of integral insulation walling systems present a different option. The best known are SIPs (structural insulated panels) and ICFs (insulated concrete forms), but there are new ones appearing all the time, including plant materials, such as straw bale and Hemcrete. SIPs have the added advantage of being a great way to insulate sloping roofs as well..

The Rise of Natural Materials

One of the big changes in the insulation market has been the adoption of natural materials. Currently, it’s mostly used by enthusiasts because the prices are high, but the market share is growing and new materials are appearing all the time. Look out for Warmcel (sprayed-in cellulose), sheep’s wool, hemp (Isonat), Hemcrete (a lime-hemp mixture) and Pavatex (woodfibre board). These materials are usually used on timber frame houses where the emphasis is on breathing walls – i.e. ones built without a conventional vapour barrier – and are usually bought via specialist suppliers. Mike Wye Associates keeps an online price list: mikewye.co.uk.

This page is sponsored by Permaseal UK Ltd

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