It reduces energy bills and the carbon emissions linked to global climate change.
It is more cost effective to spend money on extra insulation than it is to spend it on extra heating equipment, but the type of insulation is very important if you are aiming to build a sustainable house.
Conventional insulation materials include fibreglass, rockwool, polystyrene, polyurethane foams, etc and most are made from petro-chemicals. The embodied energy is very high and most also contain fire-retardent chemicals, adhesives, etc. which are released, albeit slowly, into the atmosphere you breathe. There is usually a great deal of transportation involved before the insulation gets to the wall, floor or roof of your house.
Insulation materials work by slowing down heat flow, measured by an R-value (the higher the R-value, the greater the insulation). This R-value varies according to material type, density and thickness, and is affected by thermal bridging, unwanted heat flow that occurs at window openings, wall plates, joists, studs and rafters.
Sheep's wool is often treated with chemicals to kill parasites and reduce fire risk, although it is very flame resistant in itself and some builders use it 'au naturale' with no problems. It is available locally in most areas and has exceptional insulation qualities. The embodied energy is also very low and as the sheep has had to eat grass to produce it, wool helps to reduce carbon emissions. Thermafleece is the most common commercial brand available, though you may be able to buy it from a local sheep farmer at shearing time.
Natural plant fibres that are available in batts and rolls, and typically contain borates that act as a fungicide, insecticide and fire retardant. Potato starch is added to flax as a binder. They have low embodied energy and are often combined in the same product. The UK has an ideal climate for growing flax and it is a very underestimated crop. Examples of products include Isonat and Flax 100.
Cellulose is made from recyced newspapers, cardboard and other paper waste. It is very useful for sustainable builders because it can be blown into cavity walls, floors and roofs; used as a loose fill; or as quilts, boards and batts. Like hemp and flax it contains borate as an additive. Products include: Warmcell and Ecocel.
This is compressed wood chips that are a by-product of timber producion by the forestry industry. It uses waste chips which otherwise would be useless. It is compressed into boards or batts using water or natural resins as a binder and has very low embodied energy. It also helps reduce carbon dioxide in the atmosphere while it grows. Examples include: Pavatex, Thermowall and Homatherm.
These are small clay pellets which are exposed to very high temperature that cause them to expand, ( the 'popcorn' principle) to become lightweight, porous and weight-bearing. They can be used in foundations as both an insulator and aggregate. They have excellent thermal insulation properties, but very high embodied energy due to the heating process.
Natural insulation products have many advantages over conventional materials. They are made from renewable, organic resources and have low embodied energy. They can be reused and recycled, and are fully biodegradable. They are non-toxic, allergen-free and can be safely handled and installed. They also allow for a buildings to breathe by regulating humidity through their absorbent properties, and reducing problems of condensation. This keeps the indoor environment comfortable and helps to prevent problems like dry rot in timbers.
Unfortunately, natural insulation materials are currently up to four times more expensive than conventional materials. This is mainly due to the fact that the UK does not produce enough as mainstream agriculture focuses on cereal production. This can be prohibitive to the sustainable builder, but the environmental and health benefits of natural insulation materials far outweigh their costs. Growing consumer demand combined with government regulation, agricultural promotions and rising oil prices will inevitably drive prices down in the future. Despite the high price, natural insulation is an energy-efficient, healthy and sustainable choice for a better indoor and outdoor environment.