Our six-month renovation process finally draws to a close, and now that I’m not working so hard on the house, I can catch up on our blogging about the key environmental details.
A good starting point is a summary of the insulation that went into the house: walls, roof and floor.
Our insulation choices
- Roof – Polyair Multi, a multi-layer combination of reflective foil, foam and bubble wrap. 9mm thick, it sits directly under the corrugated iron roof.
- Ceiling – R4.0 Greenstuf batts, which are conventional insulation batts but made out of recycled plastic rather than fibreglass. Manufactured in New Zealand.
- Walls – R2.5 Greenstuf wall batts, fitting into the standard studwork walls. Then R1.6 Air-cell Permishield wall wrap layered under the outside cladding, with a 20mm air-gap to allow the reflective layer to work properly.
- Floor – R1.5 Greenstuf underfloor insulation rolls, under the wooden floorboards (the house sits on piers, as is typical in Federation houses in Sydney).
So that’s six types of insulation from three different manufacturers. In each case, we looked at a range of options, and picked the one we felt would give the best outcome for a reasonable price. While there are undoubtedly a large number of possible ‘right’ choices, it shows that there isn’t a one-size-fits all product (or even manufacturer).
How does this compare to typical insulation?
This is a lot more insulation than a typical Australian house (although only a fraction of what would be installed in colder European or North American climates).
It greatly exceeds what we were required to do according to government regulations (BASIX), but more on that in a future post…
How much did it all cost?
The total spend on insulation was approximately $3,800, for a 100m2 extension. That probably seems like quite a lot, but it all comes down to the payback period.
The house had underfloor ducted gas heating when we bought it, and this will be extended to the new portion of the house. The better insulated the house is, the more warmth it will retain, and the lower our gas bills. But exactly how big a saving — hard to tell.
What we can be confident of is this: we don’t have air conditioning, and we won’t be needing it. So that’s an up-front saving of $3-5k in avoiding the purchase of an aircon unit, and then the yearly savings on electricity from that point onwards.
So the payback period: immediate. A sensible use of our money, we think.