The Construction of MOTHER'S Bioshelter Greenhouse

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Glazing: Our roof glazing is recycled 3/8" X 4' 8" X 8' 8" tempered glass that had been used to manufacture plexiglass. This isn't a standard store-bought size, so if you're unable to find recycled material, you may have to have the glass cut to size or alter the rafter spacing to suit a different size pane. Other glazing in the building may be tempered or not, depending on your concern and your pocketbook. (Tempered glass would certainly be safer, but it's more expensive than single-strength and would have to be custom-cut to the odd shapes.)

Roof glazing strips: To secure and seal the roof glazing, we set the sheets about 3/4" apart in beds of silicone caulk, added another layer of the sealant on top, pulled pressuretreated 2 X 4's down on the glass with screws through the gaps, and covered the wood with aluminum flashing.

Drainage: Water-shedding details, such as the bevel on the window sills, are quite important for preventing rot, even if pressure-treated lumber is used. In fact, we face-nailed a drip edge all the way around the exposed part of the building at the sill level. This was made by ripping 2 X 4's in half on a 30° bevel. The strip not only allows water to run off the walls but also serves as an upper stop for the rigid insulation attached to the masonry below.

Exterior doors: We made the doors ourselves. They're built up on a 1" X 3" lumber frame, insulated with 1" polystyrene board, and sheathed with 1/4" BDX plywood inside and 1" rough-sawed boards out. A plexiglass window is fitted in the upper portion, and a swinging animal-access door is set into the bottom area.

GROWING BEDS

We used two different methods of building the growing beds in the greenhouse. The bed against the west wall, which is used for propagation, is supported above the floor on 4 X 4 posts and has a base layer of rock with the growing medium above. Solar-heated air picked up at the roof peak by a squirrel cage blower (powered by a photovoltaic panel) is forced down through aluminum dryer duct and into the rocks to boost soil temperature. The beds on the south and partition walls have sealed and insulated cavities beneath them that are filled with compost. Heat, moisture, and airborne nutrients can filter up to the growing medium through treated 2 X 4's spaced several inches apart and covered with wire mesh. Solar-heated air can also be distributed to the cavities . . . to warm either the compost or the soil above.

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