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Banking soil at house to gain earth's heat

I live in a concrete-block house on the side of a gradual slope of sandy soil. The window level is about three feet aboveground on the rear (south) side and four feet aboveground on the front (north) side. It seems to me that banking sandy soil (or vermiculite) against the walls up to six inches below the windows, supporting the soil with a row of concrete blocks two to three feet high, and planting the intermediate area with shrubs would be a great way to couple a portion of the earth's temperature to the home system. What about it? David W. Feldman Panama City, Fla.

By drawing the soil, sandy or otherwise, up to the walls of your house, just below the window level -- thus reducing the exposed surface of the walls of the building to the harsher environment of the air -- you will pick up some clear benefit in the dampening effect of the soil. How much may be another matter.

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The temperature benefit could be microscopic in relation to the isolation effect you might find from running the soil almost up to the windows.

"I don't think there would be much of a heat gain from the soil, because you probably would not be deep enough into the soil," says Robert Wendt, an expert on innovative structures at the Oak Ridge National Laboratory in Tennessee.

"The first couple of feet of soil is clearly better than the air, but not nearly as good as it would be if, say, you were 10 feet down, where there is a much more uniform temperature."

In other words, what you are proposing to do is not like a cave, where the temperature is uniform the year round no matter what is happening outside. You will be too close to the surface of the ground.

A fair amount of partly underground construction has been done in Minnesota. You can write to the Underground Space Center at the University of Minnesota at Minneapolis. Also, you probably could locate an architect who would welcome the challenge.

If you were to berm up the soil around the house, you would have to make sure the walls were appropriately sealed to avoid any moisture problem inside the house. After all, the damp soil would be stacked against the house and could lead to moisture on the inside walls as well.

"If the work is designed properly," Mr. Wendt says, "this would not be a problem at all."

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