Having made it through a 17-degree night with our unheated greenhouse full of seedlings, we’re feeling better about our design! Our setup includes a number of 55-gallon barrels full of water that absorb heat during the day while the sun shines on them, and release it at night to moderate temperatures inside the greenhouse. Our seedling trays are inside insulated cold frames on benches on top of the water barrels; on colder nights, we cover the cold frames to help retain the heat from the water barrels. During the coldest night last week, we measured an overnight low of 37 inside the cold frames, and the water inside the barrels got down to around 40. We’re still making modifications (more water barrels! different arrangements to maximize both sunlight hitting the barrels and room for seedlings! and maybe painting the barrels black…) and still thinking about putting a second layer of plastic on the structure to add insulation in the fall. Heat-loving seedlings like tomatoes and eggplants are in our house, so we didn’t have to worry about them. With a little luck, outdoor temperatures will stay above the high-20s for the rest of the spring, and the seedlings should be in good shape.
In other news, the chicks are starting to look more like young adults, with full coats of feathers, and as of yesterday they have finally moved from inside our house out to a corner of the greenhouse! We’re excited to give them their first taste of foraging as it warms up outside.