It is about time I talked about how much all this is costing. So far we have managed to keep close to our estimated budget and schedule. At this point, it is looking like the build costs, excluding VAT and professional fees, will come out at £1500 per m², which, given that we are having a high standard of internal finish (hardwood floors, granite worktop, decent taps and appliances etc) is not unreasonable. If you strip out the Passivhaus elements, it would have costed £1200 per m².
I think we have learned a lot about how we will approach new Passivhaus builds to bring the cost differential as close to £0 as possible. This is something we are looking at now. For this project, the extra cost will pay for itself easily over the time I hope to be living in the building, especially now that fuel prices are shooting up - very small increases in energy prices have a disproportionate effect in shortening the payback period. There will be many other non-energy benefits for us - better air quality, much more comfort (no cold drafts or 'cold radiant') and less noise from outside, no radiators on the wall taking up valuable space, loads of natural light, cooler summer temperatures - I think all those must be worth something.