As I discussed in an earlier post, we have tried to use passive solar principles to position our secondhand house at Cheslyn Rise to take advantage of the sun’s heat in winter and to shade the house in summer. The other technique we can use to regulate the temperature in the house is insulation. Under Queensland building law we actually have to put a certain amount of insulation in the house anyway, so the only decision to be made was what kind and if we would add any extra insulation.
My first thought was to use a natural fibre, so I started to investigate options. As the use of insulation is mandated and must be a certain ‘R value’, we couldn’t just use any old scrap wool available, it has to be a proper tested insulation product. Our options seemed to be:
Glass wool (fibreglass)
Polyester (not natural, but still an option)
Sheep's wool insulation
When I started to research sheep’s wool I found that all the products available in Australia are only 70-80% wool, stabilised with polyester. Even though this polyester is mostly recycled material, I just don’t feel comfortable mixing natural and synthetic fibres. As I discussed in my post of Permaculture- produce no waste, you end up with a product that can neither be recycled or composted, it will be literally rubbish when its no longer useful as insulation.
Cellulose is made from recycled newspapers and has to be sprayed into the roof cavity. This is useful for awkward spaces, but very difficult to adjust once its been sprayed. Also, I assume that its treated with fire retardant chemicals (otherwise it’s a massive fire hazard up in the roof!). It defeats the purpose of using a natural product if its full of chemicals!
Glass wool and rock wool insulation
Glass wool and rock wool (or mineral wool) are extruded glass and rock respectively, known collectively as mineral fibre. Rock wool can withstand higher temperatures, and its better for acoustic insulation, but is more expensive. Both are natural products, made from mined silica and basalt respectively (with various additives) and can be recycled by melting them and reprocessing into more fibres (although there is no recycling plant in Australia currently, it is recycled in Europe).
The main disadvantage of using mineral fibre insulation is that the small fibres can irritate the skin and lungs, so its best to install in cooler weather, with full overalls and dust masks. Lucky for us, this is also the cheapest option, that doesn't often happen! And we can just buy them from the local hardware store (and although some product is imported, as far as I can tell, there is also some insulation manufactured in Australia, which would be my preference).
Have you researched or used a natural insulation product?
More posts about our house, from moving it to the property through to moving into the house (roughly in order):