I'm bring this old thread up on a recent article i've come across. Just something for those to think about instead of fibre based insulation.
http://life.nationalpost.com/2012/11...ht-insulation/
The context is based for Canadian homes and how advantageous close cell spray foam can be. Unfortunately, I do not believe in NZ the use of such a product will be permitted (and not to be confused with the Air Foam product we see in NZ where they cut holes in the wall and fill in the cavities). The article explains issues about air drafts and how spray foam can address this problem and thus drastically reducing the energy load it takes to heat and cool a house.