Cold frame greenhouses differ from traditional greenhouses that are constructed with heating systems. A cold frame greenhouse is an enclosure with a transparent roof that’s built very close to the ground. The top of the greenhouse is transparent to let in sunlight and keep heat from escaping through the convection process that generally occurs at night.
Cold frame greenhouses are used to extend the season of a traditional greenhouse, and to protect plants from inclement and cold weather.
Cold frame structures are often built as extensions of heated greenhouses (they are placed along the foundation). They are built on the southern side of the greenhouse as a transition venue for seeds that are planted and germinated in the heated greenhouse. The seeds can be moved to the cold frame to allow for an adjustment period before final planting outdoors.