John Hait's book goes into a lot of mathematical detail on this and he concludes that if you have 20 feet of dry dirt, you can carry the heat of summer all through the cold of winter. Thermal inertia!
Well, I don't want to have a house that is 20 feet deep, and Hait doesn't suggest that. Instead, wrap this much dry dirt around more than half of the house. He has done this more than once and the result is a home that requires no heat.
So you have a layer of structure (R 2.5 to R 5), polyethylene on the structure, about 8 inches of dry dirt (R 2.64), about four inches of wood duff (R 5.0), another layer of polyethylene and then 20 inches of wet dirt (R 1). This brings our roof R-value to about R 11 or better - pretty good! Plus, a healthy dose of thermal inertia!
Peter Ellis wrote:Adrien, I thought I had understood what Paul was talking about when he said "ATI". He made it seem pretty clear that it was his way of saying PAHS or AGS.
Those terms refer to systems where you actually run tubes under the ground in an area protected against the flow of water, transferring heat from the air into the ground during warm periods and pulling it back out when the air is cooler than the ground. It's much more than just an earth bermed structure.
Peter Ellis wrote:Net - this is a small earth bermed log cabin with a passive solar design.
Tyler Flaumitsch wrote:I was under the impression that you were going to point the gable end of the structure south to be able to replicate the terraced idea out the larger front and to see what the solar gain would be.
How do you plan on measuring performance?
paul wheaton wrote:Wofati is aligned with the hill.
Passive solar structures are aligned with the sun.
This will be an attempt to demonstrate the power of annualized thermal inertia. So we are specifically NOT aligning this with the sun. I suppose that some folks will select building spots so they can have both. But for the first one, we had the discussion and I decided that I needed to find out the power of ATI without any additional help from the sun.
E Little wrote:Are you going to be done before it snows?
There will be a temporary umbrella layer added, to be removed when the snow melts so the layers can be thoroughly dried before next winter.
The folks on the ground will correct me if I'm wrong, but based on my observation of the sketchup and going on the assumption that the RL version is somewhat similar, the posts are on a 10 ft. grid, meaning that the interior space is about 400 square feet, not counting the substantial overhangs.
Patrick Mann wrote:I'm a little surprised at how small the interior space seems to be, given the massive outer shell. What are the net dimensions of the habitable space?
Tyler Flaumitsch wrote:What will the large wall be? Cob infill? Modified stick build? Cobwoob? 1.21 gigawatt forcefield?
Miles Flansburg wrote:paul, I wonder if you can modify the roof to use the design of native hogans?
paul wheaton wrote:
569) We spent over a thousand dollars attaching the last layer of wood. I passionately want to get the cost of materials for the shell to fall under $200. So this needs to be dramatically reduced or eliminated. Starting by looking at one wall: there are two poles holding up about 30 sticks. Each stick has two, rather expensive, screws holding it in place. I want to replace that with zero screws. Let the pressure of the dirt hold it in place. I do have a concern that in this case there could be bowing of the sticks - so I propose adding a pole in the middle to prevent that.
Bill Kearns wrote:
Perhaps closer to the entryway you envision?