Cold Frames have been in use for centuries to propagate plants, the first glasshouses were in fact no more than a glorified cold frame. Originally they were no more than gently sloping glazed and timber panels set upon stone or brick walls designed to protect tender plants. A Cold Frame is a general term that depending on specific design details can have a range of names including; a cloche, a propagator, a garden frame and ironically a hot frame when used in conjunction with a heating system that the Victorians fueled using farmyard manure.
Keen gardeners find the flexibility that a coldframe provides to be indispensable, there are times in the lives of all the more familiar greenhouse plants that the glasshouse is too warm for them so an additional area in the form of a cold frame provides an ideal second temperature zone. The seasons too can cause overcrowding in a greenhouse making the coldframe indispensable especially in early spring when the greenhouse is at its busiest or in autumn when plants are being brought in for over wintering. The most important use a coldframe gets is when seedlings are raised in warmth for subsequent planting out it is not possible to harden them off without the use of a garden frame.
If your cold frame is to be used for early cropping then maximum roof glazing to captivate the sunshine is vital, but because of its portability a cedar Cold Frame can be re-positioned to a north facing position in the summer to protect and encourage autumn and winter flowering plants.