Principle 3: Obtain a yeild
Baltic pine floorboards recovered from the original building were put aside for use in the two bedrooms. Baltic pine is quite soft, and damages easily, making it inappropriate for high traffic areas. I figured that I would have enough boards for both bedrooms as the boards covered two rooms about the same size and the original kitchen (now a study / 3rd bedroom). It turned out that it was a very close call with all useable boards used.
For the remainding rooms in the building we decided on recycled hardwood floorboards. The timber is a lot more durable, easier to work with and fairly cheap (at around $3.10 per lineal metre when bought in bulk). Being narrower though, 105mm instread of 150mm, they can take quite a while to install. Each room took about 16-20 hours to install (including insulation).
I planned to have insulation under the floor because of heat losses in winter of 10-20%, as well as heat gains in summer. The options that I considered for underfloor insulation were:
- sawdust (using masonite under the joists to hold it in place) - this technique was used in old homes, but only generally in ceilings. Problems with it include a fire risk (it can spontaneously combust), and if it gets wet it can attract insects. Also installing masonite would be difficult.
- raw wool straight from the sheep (using masonite under the joists) - being sheep country, cheap daggy wool is probably available locally. Benefits include: it is grown locally, is biodegradable, does not irritate and naturally flame retardant. Unfortunately it needs to be sprayed thoroughly with borax (which has a low toxicity) to avoid it becoming a breeding ground for moths, washed as it exudes grease and sheep sweat which can make your house very smelly and it needs to be enclosed in a cavity. Another thing to consider is that the sheep may have been treated with chemicals (dipping).
- pure wool batts (using masonite under the joists to hold it in place) - a good alternative, but are expensive. Local R2 batts are $A13.50 per m2 and not available until for six months - because of the Home Insulation Program that the federal government is offering.
- rockwool - 'optimo' a new underfloor product which wasn't available at the time. I also have concerns about the amount of energy used to produce it (it's molten rock spun like candy floss), and the safety concerns as it can be inhaled (similar to fibreglass and asbestos).
- 'foilboard' - a ridgid product that could be difficult to install as joists are second-hand and not all evenly spaced.
- polyester batts (using masonite under the joists to hold it in place). Considered birdwire, but thought that it would become a breeding ground and nesting material for rats / mice. Lcally available, low toxicity, long life (50 years plus), low off-gassing and cheaper than wool batts at $A5.60 m2 for R2. It's a non-renewable resource (made as a by-product from crude oil processing), but highly recycleable.
- cellulose insulation (using masonite under the joists to hold it in place) - lowest embodied energy of the mainstream optioons, uses the most recycled content, often needs experienced installers to get the material fitted correctly. Not aware of any local installers.
- permifloor 500 - a double sided reflective foil with a thin layer of foam in between with small holes throughout allowing it to breathe. Unlikely that rodents would breed if they got in as there is no nesting material. Become less effective if dust accumulates.
- Rice Hulls - while researching this blog I found some interesting information about using rice hulls as insulation (download pdf here). It appears to be very cheap, with some great qualities (for more info see "The Rice Hull House" article). It's insect resistant and virtually fire proof (see report). It has an R3 value per 25mm according to this report.