I checked out one of the links in the alternative housing archive that promoted dry-stacked cement blocks (only the first layer mortared, the rest used some type of cement..1/8" bead) which was also heated with passive solar inputs as the only source,..no backups. One of the stated requirements was to make sure that the soil in contact with the foundation, and for twenty feet out, had to be kept dry so as to act as a massive heat sink that would transfer to the mass of the cement blocks. In order to keep this soil dry it was stated that it would be covered, in layers, with polyethylene (6 ml I think) sheets and some type of insulation also, either straw or EPS (expanded polystyrene). The heat retained in this soil is called Passive Annual Heat Storage. My question is: Is anyone familiar enough with this method to explain how the polyethylene sheets are joined to the foundation to prevent rain from seeping into this juncture? It seems a bit of a stretch to think that just laying the sheets on the ground next to the foundation will keep the soil dry enough to be a massive heat sink for the foundation. This area right next to the foundation would seem to be the critical part. If the soil at this part got wet it would not matter how dry the soil 10 feet and beyond was..the wet soil next to the foundation would be drawing heat away from the cement blocks.

-- John Fritz (JohnFritz24@hotmail.com), April 02, 2002

Answers

John, good overhangs on your roof and rain gutters that direct the rain water well away from the foundation are a good start. The poly has to be laid under a layer of top dirt. The subsoil has to be sloped a little away from the house prior to laying the poly. Then some people put the insulation on top. If you use straw you will need more poly on top then your topsoil or mulch. Make sure the house has good drainage all around it and isn't in a hollow. Are you planning on an alternative type of house like strawbale or an earthship? I built a strawbale (then sold the property so I want another!) and some friends of mine built a beautiful earthship.

-- kim in CO (kimk61252@hotmail.com), April 02, 2002.

Kim, I am currently in the investigating stage of alternative house types. The earthship and strawbale are both attractive for their use of materials that are either being recycled or have a low quotient of imbedded energy. However, what really has my attention lately is the concept of massive buildings and their ability to act as solar heat sinks..especially the type being promoted on the website http://www.thenaturalhome.com/passive.html. These seem less friendly as far as the ecology of the materials being used, but they seem more amenable to owner/builders. Plus the rumors I've heard of Dennis Weaver's home having a wall that is in a state of collapse has me dubious of the long term viability of the earthship concept. Have you heard anything about Dennis' home having this type of problem?

-- John Fritz (JohnFritz@hotmail.com), April 02, 2002.

John, sounds like an interesting project. I'm not familiar with the idea well enough to give you concrete info, but I'll rattle some ideas out of my head, and you can take from them what you will. If you are having a machine dig out the foundation of your house (basement) then I would suggest you have the excavation dug to the extreties of your themal heat area. Expend some of your resources on a bed of gravel over the whole area to facilitate drainage. Install perferated flexible pipe in the outer perimeter to increase the drainage potential. build your house, and backfill. Cover the area outside your home with your roof as much as possible, and put decks out. I've heard of a guy who put a bunch of connected barrels in a rock pit on the north side of his house. The barrels were heavilly insulated on the topside(like many feet of insulation) and the insulative material was covered with waterproof matterial, and buried well below the frost line, in soil for a flower garden. A solar water heater cycled hot water into the the connected barrels in the summer time, and he closed the system, drained his solar panel, and let the barrels of water and rocks in the pit, raise the soil temperature on the north side of his house in the winter. You could probably come up with a number of variants on these ideas. I wish you the best of luck. If you like you can e-mail me, about what you have decided, as you have my curiosity. I love the idea of alternate housing, as I grew up in some of the worst built structures on the planet, mobile trailers. Take care.

-- roberto pokachinni (pokachinni@yahoo.com), April 06, 2002.