Tom, a member of the PACCS forum, shares his experience with his first PAHS style home. His philosophy is simple: "a house should keep you dry, warm in the winter, cool in the summer, have no exterior maintenance, be cheap to build, and cost nothing to operate." A description of his dwelling, in his own words, follows.
We left Denver in '85 with a dream: live in the country in a PAHS (Passive
Annual Heat Storage) house. Central Virginia is where we ended up.
The home is cast-in-place reinforced concrete with steel bar joists holding up our 240 ton rated roof. Standard commercial construction, beefed up. Very inexpensive.
I'd intended to hire a concrete crew to pour the walls. Turned out that poured walls were very unusual here at the time. My plan frightened the few existing concrete guys. I ended up buying a how-to book, "Construction Manual: CONCRETE & FORMWORK", ISBN 0-910460-03-5. That, coupled with everything I could find from the American Concrete Institute and the Portland Cement Association, allowed me to brazenly undertake our house, my first. Hait's "Passive Annual Heat Storage" was our guide. As his dome architecture didn't do anything for me, I took only the concept. I envisioned an umbrella with everything either under or outside it, extending Hait's 20' from the perimeter. This umbrella has a very un-Hait-like form, with a number of 90º bends. General shape is a box with a bend in the middle.
After hiring 2 guys who knew even less than I did, we started. For forms, we used the venerable plywood with snap tie system. As I dislike straight lines, we formed compound curved walls. Doors and windows are arch-topped. There was a lot of head-scratching determining how to do the formwork. One has to think in terms of negative space. As a woodworker intending to build his own doors and windows, the millwork was taken in stride.
Structural engineering is critical. Our local building department was less than enthused, but with the appropriate engineering they went along. They now have had a change of heart.
The bar joists are 400 lbs each, on 22" centers. Both the crane guy and the steel delivery guy were pumping me on why I was getting so much steel. Neither had ever seen that much used residentially, nor had they any idea of cost. When I mentioned it, the crane guy, after expletives, mentioned that we couldn't have gotten a wood roof for that price. Designed total load was 240 tons.
We have 20,000 cu ft inside. Following then Canadian code I cobbled a .5 ACH (air change/hr) ventilation system incorporating from the outside: a 5 micron filter, dehumidifier (used seasonally), air-to-air heat exchanger (HRV), distribution ducting. The HRV has a 90% efficiency rate. I used plans published in Popular Science, 1986, tweaked a bit. It's not unusual for guests to remark on the quality of our air. One happy coincidence here is the natural convection current aided by the roof sloping 3' from front to back. Makes the air system work beautifully.
A major departure from Hait's plan is our lack of earth tubes. My fear, widely shared, is that in a humid summer climate they would provide a beneficial environment to grow various fungi/molds. I now understand that a UV treatment system will control potential problems, but that adds yet another active system to maintain. Not the passive ideal of PAHS.
Windows are 450 sq.
ft and 30% of exposed walls (all but N). No cave here. We use no window
coverings in our 4166 heating degree day climate. This contributes, along
with our much smaller than Hait-recommended mass and lack of earth tubes,
to our 13º annual temperature swing.
Under the umbrella we have: 1' of dirt overhead, 14' behind the back wall, a small amount on the side walls, then there's the floor, plus the dirt under the side yard, parking, garden, and front patio.
The kitchen entrance
is a door in a door. The larger one, an inverted U, allows a 6'x8' opening,
adequate for my tractor. The smaller door is 4' wide with a standard sliding
door lite in it. These are large walls, windows and doors fit the scale.
Interior doors are 3'x7'.
Exposed wall skin is copper. Cheapest (lifespan) siding I could find. Original plan was stucco. This is much better. Under the copper is 2 1/2" of XPS, then the concrete. When I did heat loss calculations I found I was over-insulated, given the windows. IIRC, I determined at the time that window treatment could save us 2º in the winter. No thanks. Steel studs support the copper. Nylon tee washers isolate the copper from stainless screws. Although galvanic corrosion doesn't seem to be much of an issue here (I'm currently testing). On the client house we used copper Z strips instead of the steel studs, allowing sole use of copper rivets to attach the sheet copper
While we don't measure up to Hait's performance, this is by far the most comfortable house we've experienced.
Since then, I've built another PAHS for a client and have a replacement started for us. There were very few changes made to our original plan, other than size and interior details. These have proved to be wonderful houses.
Tom may be contacted at