Insulation

• Forget the BCA ("barely compliant architecture") - these tell you how to build a house without being a arrested.

Floor

Options to insulate the floor (90m2) include the following. No in

• aircell over the joists, $900. Probably under-performs in the medium term due to dust on surfaces and is compressed over the joist. Easy but not great.
• infill with rigid foam between joists. >$2200 for Knauf XPS boards (bunnings). Medium effort.
• spray foam. Great air seal. Possible toxic problems if poorly mixed. Uncommon in queensland.

Infill is choosen.

XPS - good for wet. Very rigid.$$/$$$. Uses HBCD as flame retardent, which is questionable toxicity. Vapour and air barrier. High CO2equiv blower. 0/GGG. $2200 / 90m2 knauf bunnings 50mm

EPS - $/$$$. Only one which is somewhat vapour permeable.Good for wet. Ok pentane blower. GG+/GGG. Kooltherm 40mm $966.

PolyIso - urethane. Medium rigid. $$/$$$. Moisture sensitive. Foil faced so vapour and air barrier (if taped). Ok Pentane blower. GG/GGG

Polyurethene - lighter density blown with water. ?/GGG