Upon visiting a Passive House build over a month ago in Lincoln (near Christchurch), I was not surprised. The price tag on the construction + European ventilation system + imported LVL windows from Europe, the level of detail required and God O might, the amount of man hours required to build their double wall construction ; there was no sense other than "Why?" I think the whole house was 130m2 but the owner budgeted for $900K. While outside one designer told me that's the way he would build... I mentioned why not go SIPs? He said "NOISE" I pointed out in this new residential neighbourhood "You're going to get lots of noise from where? " He said the biggest concern he has with SIPs and that even a car driving in front of the house you will hear it. I dunno how true this statement is but surely it can't be as loud as conventional construction in any downtown city?
Previous comments on OSB is untrue in how much VOC contained. Also EPS is highly recyclable, just that in NZ they don't have the proper facilities to do it (but in 50 years time?). I do agree that the CCA found in treated timer is nasty stuff. But what can you do? the NZBC requires it.
When we built our house 10 years ago, I did look into all these 'green' building initiatives like the Passive House and the Godly expensive Intello-wrap membranes. While the concept is great, wifey didn't agree meaning, there are constraints. Women don't want smaller size rooms, smaller kitchens, and men don't want small garages. So it was apparently clear that conventional timber frame construction was our choice. We fully enclosed with a rigid air barrier (treated 7mm plywood) which keeps stops the fiberglass batts from moving (sagging). There was a lot that I did myself to ensure air tightness without the costly Intello-wrap. Such as special sealed electrical flush boxes. No recessed ceiling down light fixtures.
All in all, the Canadians have found a way to build energy efficient. They use 1/3rd more timber in their house than in NZ. They use inexpensive plastic 'vapour barriers' to stop moisture from passing through the wall instead of the Intello-wrap. The uPVC windows & doors are air tight (no exotic Europeans required). What is NZ doing wrong that the Canadians seem to have achieved a high level of home comfort without the high cost?
