Bruce Lepper

Hi Michael,

The site with a description of Tom's house (in Central Virginia, not West Virginia as I previously said) has disappeared. It wasn't his site but he was answering questions about his implementation of PAHS. I have a copy of the text which I am pasting below.

If you have specific questions I'll be happy to try to answer them here. I do intend to eventually publish an English version of my French Wordpress site.

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Tom's post:

Was a long time coming. 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.

Long story substantially shortened, got a CO in 1994. This 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 howto 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.

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.

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.

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 13ºF (7°C) annual temperature swing.

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.

Room for improvement to be sure. Which is one of the reasons for my involvement here.
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PostPosted: Thu Jun 30, 2005 11:26 pm    
Manu, yes thermal mass is doing all the work. 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 concrete isn't doing any "annual" work, but I don't know exactly what is happening with the dirt.

I envisioned an umbrella with everything either under or outside it, extending Hait's 20' from the perimeter. We live in the woods, don't own a lawnmower, and stopped the umbrella where we wanted to keep the trees. 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.

What I would very much like to learn is how best to effect performance change. The next house, out of the ground but on hold, will have twice our overhead mass, Hait's recommendation. I believe that will greatly improve our annual extremes. But it would be nice to not be experimenting.

Your unearthing cooling degree days is something I need to spend some time with. Was not anything I had available when we were building. My current assumption is that we need more mass, particularly overhead, to aid heat absorbtion during the summer.

One thing I learned on house #2, for a client, was that I was mis-informed about steel pricing on my original. #2 had a 40' clear span (30' here) and the steel cost was only moderately more. You buy steel by the pound, as I was told, but you don't pay as much per pound for larger steel. That was the big surprise when we were designing #2.

Those bar joists were 600 lbs ea, on 17" 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 300 tons.

The HRV solely reduces the penalty of air changes. It turns out mine is upwards of 90% efficient. 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.

Scans of the Popular Science article are available. Also digital pics of our house, but I would have to send them direct. Pretty sure I mentioned that I'm a novice.

Something else that I'll throw out. My strong interest in thin shell concrete structures, buried of course. Our local engineers didn't have a clue. A Monolithic Dome designer acquaintance assures me that his engineer can do what I need. Unfortunately for me, the engineer has apparently gotten very popular for large projects. I don't find domes particularly attractive but would very much like to make a hyperbolic paraboloid. The legacy of Felix Candela is awe-inspiring. Anyone unfamiliar with his work is in for a treat. Search Xochimilco restaurant, among others. The common problems of that construction would be alleviated by going underground.

Rather than balloon forming, like Monolithic, or wood forming like Candela, I find dirt forming as Paolo Soleri did at Cosanti much closer to my abilities. Dirt I can move, and you need a large amount of it for PAHS. This makes double-duty for the dirt. First as the form, then dig it out and pile it on the structure.

More than you asked for. I'll stop now.

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Here's a photo, not of Tom's house but of another successful PAHS build, that of Christian in Romania.
His descriptive site is here: https://www.builditsolar.com/Projects/SolarHomes/Romania/CristianHouse.htm

Hi

I'm familiar with Hait's book and used it to build an experimental and documented PAHS house, which I briefly describe in https://permies.com/forums/posts/read/147155. I spent a long time seeking information, as you are doing, and there ain't much of it out there. Fortunately I ran into Tom in West Virginia, builder of at least three PAHS-based homes, who patiently  passed on to me all he knew.

The result is a comfortable house which needs no heating or cooling or mechanical ventilation here in southern France. The PAHS concept also enables a usually-overlooked but immensely important climate feature - you can build with a reinforced concrete skeleton infilled with rammed earth walls. We protected the walls with discarded swimming pool covers but in any case Hait's insulated and waterproof umbrella, which extends 20 feet (6m) around the house creates a moist but never wet, warm, stable environment which enables the use of rammed earth without risk (as long as you have checked there are no underground streams or high water tables). This fits perfectly with excavating into a south-facing hillside and using the earth to build the house and berm the sides. Such sites are common and are often too difficult for agriculture, so it's a win-win situation for the climate and the economy. No need for a concrete pad as you've probably got into hard stuff after the excavation. The front concrete pillars are on individual pads, and for the floor we used a 2" (5cm) thick truck-delivered anhydrite layer on top of stones and roadbase and its holding up fine. See the pictures on our blog www.blepperblog.wordpress.com. Sorry, the blog is in French but the pictures aren't.

We used much bigger windows than Hait, almost the whole south side is in glass which gives good wintertime heat input but imposes the use of electric external shutters so we can modulate heat input if necessary in summer and autumn. Radio-controlled shutters were probably a rarity in the 1980's when Hait was conceiving this system during the great oil crisis.

Hi

Have you thought about a modified PAHS system? That's what we did and we've been living in it comfortably for the past three years, no heating, no cooling, no mechanical ventilation, no insulation under floor or behind the walls - and with PAHS you can even build the underground walls of rammed earth and a post-and-beam reinforced concrete frame. We have a blog (blepperblog.wordpress.com) unfortunately in French but mostly in pictures describing the whole job and including temperature and humidity readings over the past two years. For ventilation we have implemented Hait's theory of automatic counterflow with entry and exit pipes running next to each other, but not the bends under the umbrella that he proposes, ours run straight down the hill to the end of the garden to avoid any possibility of standing condensation and they are quite shallow for practical reasons, about three feet (1 meter) deep.
Rammed earth has advantages over concrete (natural hydroregulation, no need for plaster finish, it's free, emits no co2, is reusable, and if you choose the site it is right there, no need to transport it) and a similar conduction capacity for heat transfer into the earth. I would add that hand-ramming earth is a great experience, very fulfilling, but don't do what we did, ramming the whole west_north_east sides with the first run about 5 feet high and then going around a second time, meaning we spent half our time trying to protect our work from the rain. Do a third at a time, covering with a third of the roof each time.

Here's a link to a Google Sheets chart of our temperature readings:

GoogleSheets temperature chart

For info, I contacted Tom Beaudette, the builder, designer and first owner of the house in Missoula, and asked him if the house performed OK. He replied this:
"We lived in our PAHS home for 20 years.  It performed as expected.  With growing family, we ended up bumping up around half of the house above grade with a super insulated 2nd level.  We sold in 2005"