Passive Solar Heat Winter Greenhouse
In 2012, based on the Northlands Winter Greenhouse model taught by Carol Ford and Chuck Waibel at the Midwest Organic and Sustainable Education Service ("MOSES") Conference attended by Jennifer in LaCrosse Wiscsonsin in 2010, we designed and built a Passive Solar Heat Winter Greenhouse. This greenhouse uses all natural heating from the sun in order to grow certain crops in three Fall/Winter seasons. It is dug down below the frost line to generally prevent freezing, and a wall of cinder block lines the outside under the double-wall polycarbonate greenhouse exterior. Perforated drain pipes are situated in the ground and connected to ceiling-height stove pipe with in-line vent fans. Over the pipe below the surface lies a bed of large gravel, landscape cloth, and then soil filled back up to ground level. 55 gallon drums of water line the North sides. The gravel and water drums act as thermal mass. The greenhouse is built on the South side of the existing barn, with the proper angles,strategically designed to capture the low arc of the winter sun. The North wall (the coldest side in Winter) is insulated against the barn wall. When the sun heats the greenhouse during the day (and it gets 80 degrees even in mid-winter), the in-line vent fans pull the hot air from the top of the interior of the greenhouse and blow it down into the ground where it heats the bed of gravel. The sun heats the water in the barrels during the day. The barrels and gravel emanate their warmth into the greenhouse at night when temperatures in the greenhouse cool. This is a super-charged growing environment, also used for seedling starts (tomatoes, onions, leeks, Kohlrabi, etc.), in the Spring. The back-up propane heater is set to 45, but rarely is activated, except when temperatures remain sub-zero with no sun for several days. Soule Solstice Farm will also be growing microgreens in this special greenhouse beginning Fall 2015. We use a shade cloth in Spring and early Fall. Vents and Fans work in unison to cool things down, even in January and February. See, The Northlands Winter Greenhouse Manual, A Unique, Low-Cost Solution to Vegetable Production in Cold Climates, Ford, Waibel, 2009.