ASK OUR EXPERTS
(Page 2 of 3)
March/April 1984
By the Mother Earth News editors
In answer to your second question, there are various ways to add thermal mass to a greenhouse that has insufficient heat storage. If you haven't done so already, install insulation under either the floor or the ground-level growing beds. Put down 1" to 2" of extruded polystyrene, top that layer with a vapor barrier, and finally, add 4" to 6" of concrete for thermal mass. (In addition, be sure to insulate the sides of the slab.)
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If standard oil drums are too large for your greenhouse, try using narrow (12" or 18") Kalwall tubes, which are fiberglass containers. These are available from Solar Components Corporation, Dept. TMEN, P.O. Box 237, Manchester, New Hampshire 03105 . . . or you can order a $2.50 pamphlet from the New Alchemy Institute (Dept. TMEN, 237 Hatchville Road, East Falmouth, Massachusetts 02536) that tells you how to build your own. For maximum heat absorption, you should dye the water a dark color (water dye is available from Solar Components Corporation). There are also a variety of plastic industrial containers that can easily be recycled as water receptacles. Do make sure that any scrounged container is airtight . . . and keep in mind that it's going to be exceedingly difficult to repair a leaky tub that's located on the lowest tier of your "water wall" if half a ton of liquid is balanced in vessels above it! Five-gallon containers are generally easier to stack than are smaller ones, though almost any receptacle will work.— Bill Smith.
Bill Smith is an energy-conservation specialist at the New Alchemy Institute.
My husband and I own a small homestead in southeastern Minnesota, and we plan to build a superinsulated passive solar home in the near future. Before making any definite plans for it, though, we need some advice. Rather than making the walls 10" thick using double studs and roll insulation, wouldn't it be cheaper, and the building just as well insulated, if we used 10" concrete blocks with vermiculite or foam insulation? I'd also like to know if this idea is safe, since I've heard that foam insulation might give off formaldehyde gas, which can cause various illnesses. Would those noxious fumes penetrate the concrete?
