Mother’s Solar Greenhouse

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The finished solar greenhouse.

Right this chilly, finger-nipping moment, fresh lettuce leaves are luxuriating in warmth and plump red tomatoes are “a-poppin’ their seams”  in MOTHER EARTH NEWS’ all-new solar greenhouse!

You see, the folks at the Eco-Village were so excited about this magazine’s series of seminars that they could hardly wait to start some hands-on building and experimenting of their own. So, before the first session had even begun, MOTHER EARTH NEWS’ eager helpers “jumped into” one of our long-planned “on the property” projects: the construction and testing of a solar greenhouse.

The 12′ X 16′ “ray catcher” (which, like any other truly solar greenhouse, is designed to utilize sun-given warmth for its only source of heat) will serve both as a demonstration building to help spread the solar “word” and as an experimental station for conducting indoor plant-growing projects. The structure went up in three days, but our staff didn’t do the work all alone. Nope, Joe Costion, Buck Orndorff, and members of Wooster, Ohio’s Wayne County Community Action Commission (all of whom were referred to us by the folks at Solar Greenhouse Digest) provided much of the necessary brains and brawn.

The finished plant house–an all-out solar structure–has absolutely no backup heating system, so this year’s winter vegetable crop could conceivably get “bit off” by frost. But folks ’round here are betting that we’ll have a bumper hothouse crop instead, because even though the greenhouse may appear to be plain and simple, the building has been designed from the ground up to catch (and hold!) heat efficiently.

For one thing, both the greenhouse’s south-facing windows and its roof overhang are angled to admit as much solar radiation as possible on that “unsunniest” day of the year, December 21 (and to keep down the amount of sunlight admitted on June 21, the summer solstice). The radiant heat that is collected in our gardener’s dream house is pretty likely to stay there too, because the back, sides, and ceiling of the “plantitarium” are stuffed with R-19-value insulation while the layers of the building’s double-thick windows (consisting of a Lascolite brand fiberglass outer shell and an inner ultra violet-inhibitor-treated polyethylene film) are separated by an insulating air pocket.

Along with these heat-capturing attributes, the greenhouse also has a great deal of thermal mass. This heat-absorbing “bulk”–provided by our tilled planter boxes, the underlying gravel floor, and 10 water-filled 55-gallon barrels that have been painted black and stacked along the north wall–will store the building’s carefully gathered radiant heat during the day and (slowly) release that precious warmth at night.

Of course, our indoor gardeners don’t want the sun house getting too hot either! But never fear, our solar architects have taken care of that danger by constructing roof and side vents that will soon be fitted with automatic, temperature-controlled “porthole openers.” Besides, the same thermal mass that keeps the building from getting too cold on wintry nights will help keep the plant home from overheating on balmy midsummer days. And–on top of all that–if the vents and the heat storage capacities STILL aren’t enough to protect our flora on some downright tropical August afternoon … well heck, somebody can always prop the building’s door open!

As you might imagine, MOTHER EARTH NEWS’ green thumb gang figures it’ll take some time to learn all the intricacies of presetting the vent controls, adjusting the amount of thermal mass, and figuring out which plants will grow best (in which sections ) of our solar greenhouse. Besides that, those tinkerers may well come up with one or two design improvements of their own to test!

Through all this experimentation, we intend to maintain complete plant growth and greenhouse temperature records … and to keep you posted on our results. Our careful monitoring should prove especially useful in the future, because this particular solar greenhouse is just the beginning. We plan to eventually build more and bigger sun catchers (both free-standing and attached to other buildings) to prove that sun-heated greenhouses can make a big difference in creating local food independence.

As for the single-family-sized building we’re working with now … well, pad’ner, we’ll know by the time the snow melts if this crop producer works as well as we expect it to. (And this is one experiment where we’ll be glad to eat our results.) If the solarium does meet our expectations, we’ll announce the availability of a full set of plans in an upcoming issue so you can learn exactly how to build your own solar greenhouse. That way come next winter you’ll be able to chomp into some “February fresh” vegetables too!