hhhmmm, the usual to look for :

material expansion issues around foundations, moisture ventilation (signs of mold) in cavity, fire blocking where needed between floors (i hear sprinklers are commended sometimes for these houses),...also passive spaces may not always be "engineered" as 'refinely' as the designers may have intended, ....ask about potential overheating issues.


just some thoughts

make sure the vents are operating. otherwise it'll get mighty hot in the summer.

good luck, i worked on a few in germany that are pretty interesting. it seems to be slowly gaining attention stateside.

Isn't it still true that a superinsulated house is actually thermally better (and cheaper) than a double envelope?

I've read articles arguing the effectiveness of the double envelope on both sides. It seems that most of the articles say that a double envelope is definitely more expensive to build than traditional houses but I would be buying an already constructed house. If anyone has some concrete facts about which style is actually thermally more efficient I'd appreciate it.

i thought the advantage of a double-envelope system was that it provides the heating system. a superinsulated house still needs a heat source.

i'd never even heard of it, so i googled it. it's not a very common form of building, a bit of a 70s throwback. the principles of a double skin are more commonly used in the building industry. i agree with sandroad; from the sound of it, the double envelope sounds overly complex and expensive to build. you could achieve similar results with thorough insulation or if you wanted to take that a step further use more conventional means of passive solar heating and cooling. the cavity between the walls also sounds like a genuine fire risk. i'm sure it's more environmentally friendly than conventional building, but not worth paying a lot extra for unless you desire it for the novelty. all that being said, that's only my first impression from reading a few articles about it.

The "convective loop" idea in double envelope houses is a theoretically sound idea, it's just that it's tricky to pull off... if you're really interested, get some of the heating / cooling bills from the last several years of it's occupancy. Get a very good home inspector to look at it. Maybe a mechanical engineer who has some specific knowledge... a smart local architect maybe. I'd even talk to the neighbors. Seriously. I guess what I'm saying is don't rely on the theoretical -- that is, how such houses SHOULD perform, but rather on the performance of that specific house itself. That's the only "concrete" facts that are going to matter.

Is this your first house, by the way? How old is it? Even if the numbers show that the house is some amount better in terms of thermal performance, I'd probably pass.... this kind of house has some extra complications -- not knowing what the other "pros" of the house might be, I'd probably buy something less potentially glitchy.