A Passiv Haus in Urbana, Illinois
by Lloyd Alter, Toronto on 01.23.08
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
it is my goal to turn my 40 year old house into a passiv haus. I have been reading the standard for a bit and really all houses should strive for this low energy standard. Luckily the house i have has 6 giant south facing windows that on a -30 degree (celcius) sunny day the temperature in doors can reach 28 degrees celcius! and that is with 2 pane windows from the 70's! Needless to say a sunny day will heat the house for about 3 hours after the sun goes down. My house is very air leaky, you can feel the air leaks all over the place and still the sun can keep the house toasty warm where we have to open the windows.
I have started by replacing all north and east windows with the exact same thermotech windows mentioned in this post, luckily i live only 1 hour away from the factory. Yes the windows are made of fiberglass and are very hard and well made. I chose to go for the most efficient windows i could being triple pane, with all the argon and glases that could fit. Price wise for 4 windows all roughly 4x3 casements came to a total of $3500 Canadian, not a cheap price but they will pay themselves off over the years. I have quotes for my 7x7 south facing windows coming in at 2000 a window but given my heating success so far with the passiv design it is well worth it. After my windows are replaced i will be placing thick straping around the outside of the house where i will have an icynene guy fill the gaps to fully seal the house from top to bottom, i was given a very rough quote of $250 per square metre. So for anyone interested in fallowing this standard the above prices will give you a general idea of what you would be looking at price wise using similar material. If this standard can partailly work in northern canada it is worth fallowing
It's my belief that not every experienced contractor could build such a house. It's not as easy as this article makes it sound. Oh, sure, "just make it air tight and insulate it" sounds easy, but something as trivial as a poorly installed keyhole could ruin the thing. Want a garage? Too bad. There are no garage doors available that insulate anywhere near enough.
Still, it's a wonderful concept, and in my opinion it should be made mandatory for all new houses. Unfortunately, legislators aren't too keen on new ideas, for reasons unknown.
Keeping the basement warm is going to be an important part of keeping the whole house warm in a structure like this. The dirt near the surface will freeze and suck off a lot of heat during the winter, and even lower down, you have an effectively infinite mass to draw off heat -- insulating against that means that you can keep the air in the basement relatively warm, thus avoiding having all that cold air down there sucking heat out of your living space.
While I'm not a structural engineer, I'd be absolutely stunned that if balloon framing wasn't approved for new construction -- as long as the numbers work out, it should be fine. The switch to platform framing mostly happened for cost efficiency reasons after the war, because it could be constructed with eight foot studs instead of sixteen or twenty foot ones. As they're using an engineered wood product, there aren't any real length concerns. Additionally, they're possibly using less mass in wood -- certainly, less mass than if they'd built a double wall or used 2x10 studs, and a lot of it is in strandboard, which a more efficient way to use wood anyway. The downside, of course, is all of the added adhesive and processing energy used in making the beams; I'm not sure if it's a net win there, ignoring the direct benefits to the building.
Not much of an overhang for the southern wall. I'd be concerned about too much heat gain in the summer. Maybe she could incorporate some of the narrow solar water heating panels made by solarroofs.com for shading. They're 12' x 20" and 2 of them would make good shades above those front windows.
full disclosure: though I get wholesale pricing on equip from solarroofs.com, I am not a stocking distributor and do not receive any compensation from them. (I just really like their setup and ease of installation !)
@ Alex,
That your home reaches a temperature of 28 C suggests that your home has very little thermal mass, i.e. there is no buffer for the heat. If you replace some light inside walls by stone or loam you will not have excess temperatures during sunny hours and the absorbed solar energy will be released slowly over a longer time, so that you can turn down the heating even on a cloudy day after a sunny day.
In most states baloon framing is an acceptable practice. It is good to see people are exploring alternative construction. Check out a simple solution that is already in place and very competitive with wood framing. It is the Ultra Frame from: www.transconsteel.com
The only problem with ballon framing would be if it was done in the old way, without fire breaks (horizontal members in the stud bays to avoid chimney effect), otherwise no problems.
@pieter
you are correct there is currently no thermal mass in my house, the floors are thin and the walls are dead air, i plan on placing thermal mass stone in key areas to absorb this heat, building thermal mass inside of existing walls is a good idea that i hadn't thought of.
Wonderfully, Klingenberg is also building affordable homes to this standard - she is working on the second one now - her site lists a sales price of $120,000 on it.
http://www.e-colab.org/ecolab/Fairview2.html
@ Lloyd
I think that putting your own comments throughout the article really breaks the flow and makes it difficult to read. Please put your comments at the end in future.
Also I don't think ice will form on triple glazed windows...
Thanks
Benjamin
In response to Benjamin, I like the comments near the text being commented upon, but I think they would be best as separate paragraphs.
Shouldn't there be an overhang above the first floor windows? As it is you would get excessive sun in the summer.