How tall should i make my cold frames

[slappy]

When i took over my allotment there was some old PVC double glazed windows that i thought i could make into cold frames.
Is there an optimum height i should make the front and back of the cold frame ?

Thanks in advance.

[Bren In Pots]

Those I've seen are usually 12in front 18inch back but really I suppose it depends on what you plan to use them for. Hope this helps.

[ESBkevin]

The sort of size Bren in pots mentions, but in the main use what you have. It's no use having free UPVC windows and then spending £100 on timber.
You could consider having one somewhat deeper so you could hot compost in the winter and grow on the hot bed.

[burnie]

I shall also be building cold frames with double glazed units, I intend to have a glass front as well to get more light in, so 2 foot at the front with a 6 inch pitch to the back, this will hopefully give me the height to grow some late tatties in for Xmas dinner.