The Construction of MOTHER'S Bioshelter Homestead Greenhouse

Work continues on our project to build a self-reliant homestead. Here is a report on one of its more important buildings, the bioshelter homestead greenhouse.


| May/June 1985



bioshelter homestead greenhouse - windows closeup

Some of the windows are hinged at the top so they can be opened.


MOTHER EARTH NEWS STAFF

Bit by bit, we have been making progress on our plans to build a self-reliant homestead, and have given you glimpses of new construction at the site. This time we offer the construction details on our latest project: a "bioshelter" homestead greenhouse that integrates plant propagation, food production, and chicken and rabbit quarters. This unique family-size structure gets its winter warmth from the sun, livestock body heat, actively decomposing compost, and — in the coldest weather — a catalytic kerosene heater. (It's also specially designed to distribute maximum heat to the growing bed's soil, increasing production by boosting the bed temperature to 80°F.) As you can imagine, this multipurpose structure is rapidly becoming the hub of horticultural activity at the homestead. We'll report more on how it works — and how to work it — as we gain experience. Here we'll go into building it.

The structure of the greenhouse is conventional. Six-inch block walls — reinforced in alternate cavities with concrete and 1/2" steel rods — rest on 8" x 12" poured footings. All of the masonry walls are either backfilled or bermed up with earth for energy efficiency. Above the grade line, stud walls rise with insulated 2 x 4 framing. The roof framing consists of rafters on 24" centers. In the rear, 2 x 6 rafters are covered with 1/2" CDX plywood, 15-pound felt, and roll roofing. The spaces between the 2 x 6's are filled with fiberglass batt, a 6-mil vapor barrier is stapled to the underside of the rafters, and the interior is finished with rough-sawed, random-width, board-and-batten siding. The glazed front roof must bear the weight of 3/8" x 4' 8" x 8' 8" sheets of tempered glass, so the rafters under the joints of the panes are full 4" x 6" beams. Alternate front rafters are 2 x 6's, and all the lumber contacting either glazing, sills, or growing beds is pressure-treated.

The Assembly Diagram should offer sufficient detail to allow anyone with building experience to duplicate the greenhouse, but we'd like to share a few extra notes and tips that may be helpful.

Notes on Construction

The code: In our area, building inspectors are mainly concerned with residential structures and other buildings that have utility-connected electricity. For that reason, there were no restraints on how we built what is essentially considered, in Transylvania County, North Carolina, an outbuilding.

Though we're confident that our greenhouse is structurally sound, you may find that aspects of our design won't meet your local code. For example, below-grade, 6" block walls — no matter how well reinforced — aren't allowed in some areas. So be sure to check with your building inspector concerning the details of this design before you begin construction.

Should you earth berm? Banking the walls of a building with earth is a good way to minimize heat loss if the site lends itself to such a technique. We happen to have quite suitable slope and soil for earth sheltering, but we wouldn't necessarily recommend it if you're building on flat ground or in expansive clay. Instead, you might want to build with minimally reinforced concrete block (or simply frame the entire structure) above ground and increase the insulation level. There's also a good chance that this approach would prove to be less expensive.





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