A Passiv Haus in Urbana, Illinois

Jonasrisen of Greenline turns us on to Katrin Klingenberg's house in Urbana, Ill, that was built to the German Passiv standard. "The program specifications were written for Germany," she notes. "But the climate here in Illinois is way more severe." The great thing about looking at this house is that it becomes apparent that it is not an impossible standard to reach, it just takes good design, careful execution and a s**tload of insulation. You start with a boxy house- "The surface/volume ration has to be very good you do not want to have a lot of nooks sticking out of your house because you lose energy."
(comments by me are in italics, and are not meant as criticism of this remarkable project, they are simply questions and comments that I have.)

Starting at the foundation:, there is an extraordinary 14" of styrofoam reaching R-56 under the slab. The basement walls are R-24. (I don't know why one would go to so high a value under the slab, other than it is easy to do so why not?) It is going to be one comfortable basement.

A conventional house might have 5-1/2" studs and perhaps some exterior EPS (polystyrene) insulation to eliminate thermal bridging through the wood; Klingenberg has cleverly turned truss-joists on their ends and used them as studs, giving a 12" cavity which she has filled with blown-in fiberglass insulation. (I would think that over time blown in fiberglass will settle a bit, leaving a gap at the top. Perhaps a spray-in like icynene could be considered)

Tremendous care was taken to preserve the integrity of the vapour barrier on the interior; air infiltration through nail holes in the barrier can cause a lot of air leakage. Klingenberg put the electrical outlets in the floor and found wireless light controllers for shallow surface-mounted boxes so that no wires and boxes would penetrate the membrane. (still, a lot of punctures can happen when the drywall is installed. another technique is to cross-strap inside, keep all the wiring inside the vapour barrier between it and the drywall, and fasten the drywall to the cross-strapping)

Windows are modestly sized on the sides and rear, big to the south for solar gain. The windows are triple glazed, argon-filled, low-e from Thermotech; Klingenberg says that they are the best in North America. (I was worried that they were vinyl but they are evidently pultruded fiberglass, which, while expensive, last forever)

You could suffocate in a house built this tightly if it did not have a big honking heat recovery ventilator (HRV) to bring in fresh air and exhaust moist interior air. (in winter enough moisture is given off from our bodies, cooking and showering that windows would ice up and mould could form) This is the biggest I have seen in a house, with very sophisticated controls to bring air in through a 100 foot long earth tube to preheat the air, and dampers that switch it to a conventional outside outlet when air temperature reaches 55 degrees F. There is a 1000 watt toaster coil in a duct in case supplementary heat is needed (1000 watts! 10 lightbulbs can heat this whole joint when it is 10 degrees below zero!) but last January the electrical bill (for everything) was only thirty-five bucks.

It did cost more than a conventional house, but Kingenberg notes " the construction is actually standard balloon framing, (Balloon framing? for 60 years this has been replaced with platform framing. But balloon framing certainly would be more thermally efficient. Is it legal?) and it is my belief that an experienced contractor could build such a house for about 10 percent more than a comparable home—an amount that could be easily recovered in energy savings over ten years." (She said that four years ago- I suspect the payback would be a lot faster now)

So how simple is that? a tight, efficient plan + careful siting to max out the passive solar + lots of insulation gives you an almost zero energy house. This ain't rocket science, it is just good design. ::Greenline, PDF of Energy Design Update, ::Ecolab

Tags: passive house

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