Insulation helps smooth out extremes in temperature between inside and outside and can help in both the winter and the summer months keeping the indoor climate within a healthy and comfortable temperature range with a minimum of added heating or cooling assistance. It needs to be applied to the whole building envelope to be properly effective, but if you are retrofitting the ceiling is the most important as heat rises. (42% of heat is lost through the ceiling, 24% through walls, 12% through closed windows, 12% through ventilation and 10% through the floor.)
Criteria for selecting insulation material include a good insulation value or R value (the range is R1.6 to R2.4 depending on what part of the country you are in and where you are putting the insulation); ease of installation; fire resistance; insect and fungal resistance; not damaged by moisture; and not causing corrosion to other materials, particularly metals. A healthy and environmentally friendly insulation material includes the additional criteria of having no irritating particles, and no or low toxicity additives, and preferably from natural source materials.
Commercially available healthier insulation products
There are now many commercially available insulation materials that, although not necessarily totally natural, are a much healthier alternative to glass and mineral fibre insulation.
Wool has always been regarded as a good insulator for clothing, and has been developed into wool batts or loose fill. Keeping the loft of wool is important for the insulation value, and as wool tends to felt down the product needs to be bonded with resin or thermally bonded with polyester to keep its loft. Wool can absorb and release moisture without affecting its insulation properties. The addition of borax makes it fire retardant. Wool is healthier for the installer and the occupant, and better for the environment in its production and eventual decay.
Cellulose Insulation is generally made from recycled macerated paper, blended with glue and blown into the spaces between timber framing. One needs to be careful about what paper is being used, coloured printing inks can contain toluene and benzene. The glue used should be a water-based, PVA type, and the fire retardant should be borax. Glue is not needed for ceiling insulation, but it may need to be covered with a layer of building paper or timber boarding to prevent the paper and dust from blowing around.
Polyester Insulation is available in batt form, and provides a good alternative to those allergic to wool. It has been known to cause some allergies as a pillow stuffing, but this has been put down to the fact that the pillow cover fabric is not fine enough to prevent the smallest fibres from escaping. Although a synthetic product (therefore it takes longer to biodegrade), it is non-toxic and in fact gives off less fumes when burning than wool.
Pumice is a naturally occurring lightweight volcanic rock that is found in many parts of the world, but resources are limited. It is a sponge-like material, porous glass froth formed by expansion of gases when molten lava cools rapidly after a volcanic eruption. Due to its toughness and durability it has been used as a lightweight aggregate in concrete for over two thousand years. It is an inert material and therefore has no reaction with any of the ingredients of concrete and steel. It can also be used as raw material for under slab insulation, but it is difficult to compact.
Wood Fibre Cement Boards are composed of wood-wool impregnated with cement in slab form. They are light-weight, durable and strong. The fibres are mineralised, a procedure which retains the mechanical properties of the wood but stops the process of biological deterioration, rendering the fibres completely inert and increasing their fire resistance. They are then coated in Portland cement, bound together under pressure in order to create a stable, resistant, compact and long-lasting material. The slabs are normally used for wall and ceiling acoustic linings but they can also be used as an under concrete slab insulation.
Alternative Insulation Ideas
Several natural materials are eminently suitable as insulation materials but are either in the strictly experimental category – that is there is no product acceptable to New Zealand building standards – or there are overseas products not available in New Zealand. So to use them requires research and persistence to get them accepted by your local council. They include clay coated straw, perlite or vermiculite, cellulose board, wood fibre boards, coconut fibre board, flax slabs and hemp. Also a layer of bottles set in sand can be used as an under slab insulation.
For more information check out the following websites: www.planetaryrenewal.org; Construction Resources; Natural Building Technologies; www.buildgreen.ndo.co.uk; Woodfibre Floor Boards; www.wohngesund.at/daemmen/kokos
If you are interested in more information on Ecological Building Materials, the Building Biology and Ecology Institute has an Eco Products and Services List available for $20, which lists building products and related services available around the country.
For more information please contact:
Wellington Office – P.O. Box 1364, Wellington, ph (04) 801 8180.
Auckland Office – 1-697 New North Road, Mt Albert, ph (09) 479 3161.
Website www.ecoprojects.co.nz
Email bbe@ecoprojects.co.nz