For the record, I'm actually retrofitting my house in Calgary with one of the more serious passive solar systems of any house in Calgary, and in every case I've got a cost plus contractor for my personal house. I'm doing the exact numbers, comparing the real cost in dollars per tonne carbon, and I care enough about it to put my own money on the line to do it. But the claim that it is cost-effective today, in my view, is not a real claim.
On December 7th, 2006. See this statement in context.