Selecting A Greenhouse
Solar vs. Supplemental Heat

There is a distinction between greenhouses that are heated largely by the sun and those that receive supplemental heat. In all but the deep South of the United States, the sun is never directly overhead, but moves across the southern sky from east to west. Its arc is higher in the summer and lower in the winter.

Solar greenhouses are meant to maximize light and heat, and to heat with the same light used to grow.

Most solar greenhouses have a north wall made of a dark, heat-absorbing material such as stone or black barrels filled with water, to store daytime heat for nighttime use. (Raised soil-filled beds also contribute to heat storage.) These substances, which have a high thermal mass, absorb the sun's energy during the day and slowly release the heat during the night. The east and west walls are often half-solid because sunlight will hit them for only part of the day.permanent The southern side, which always faces the sun, is fully glazed, and is angled so that the sun's rays hit it perpendicularly during the seasons of maximum greenhouse use.

Solar greenhouses often have two layers of glazing with an air space in between to insulate and reduce heat loss at night, while allowing light to pass through. See Greenhouse Climates for information on different climates for growing plants.

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