THE MATERIALS
blankets and fleeces:
Soft batts or rolls of insulation are easy to fit between joists, studs and rafters. The cheapest option is glass or mineral wool, which has good thermal and sound insulating properties, but is irritating to skin. Sheep’s wool, such as from Thermafleece, is a good alternative with advantages including being kind to skin and enhanced breathability and sound absorption. ‘Sheep’s wool is made from keratin, which can absorb and release more moisture and even remove indoor air pollutants,’ says Mark Lynn. The other fleece option is hemp, a sustainable plant crop that is more breathable than mineral wool, can absorb up to 20 per cent of its weight in water, and absorb noxious gas. If space is tight, look at Thermablok Aerogel, available in blankets and boards, which uses Nasa-developed technology to eliminate cold bridging (which impacts on efficiency) while being breathable. It’s super thin – just a 10mm thickness can increase the insulation factor of a solid wall by up to 67 per cent.
rigid boards and foams:
There are a range of board options, the most common being ‘closed cell’ foam slabs, such as PIR (polyisocyanurate), PUR (polyurethane) and phenolic.
Most are impervious to moisture. For a natural option, look at wood fibre board, which is made from timber waste, so is largely renewable and recyclable, has some humidity control and offers good acoustic performance. Boards need to be fitted together tightly, but avoid in awkward areas as cutting around details without gaps is tricky.
spray-on and Loose fill:
Ideal for filling every nook and cranny, these insulations form a seamless layer. Cellulose, such as from Thermofloc, is a loose-fill option made from recycled newspaper. It can be poured in place or blown into voids and gaps. It’s ecofriendly, breathable and gives good acoustic and thermal properties, and is suitable for roofs, floors and walls. Also look at Icynene, a spray-on insulation with an ‘open cell’ composition that, on application, expands 100-fold in seconds to seal all gaps, service holes and hard to reach spaces, minimising air leakage and cold bridging. Icynene offers high performance yet allows buildings to breathe. It can be injected behind panelling or through small holes drilled into lath and plasterwork, minimising damage to period homes.