The ones on the gardening shows almost always have glass.
I watch a lot of gardening shows in the winter, and here's a hint to heat them. This is what they did before electricity. Raw manure in the bottom. I think they had a layer of ready to use compost over it and planted straight into it. I would imagine it would work to settle the pots down into it though. That is, if you want to mess with raw manure.
i have tinted windows-will they work??
someone told me to dig down 4ft then put in 2ft or manure, then cover with 2ft dirt and that will give your coldframe heat. Also said to just use bails of straw for the foundation(holds heat)and lay your window on them at the desired angle.
I think there is a difference here...a coldframe is just that- cold. Using the manure for heat makes in technically a hotbed. I have just started using coldframes the last 2 years and mine are very "homemade". I had a lot of the large cement block bricks and old windows. I made the "frames" with the bricks and just put the windows on top of that. It works very well. In fact, I don't really want the "constructed" frames because I find these very convenient to rearrange, break down, move around and later in the season I replace the windows with boards and use them for shelves under the trees for all my hardening off. I live in a mild winter climate, and don't heat them at all. The seeds germinate when the weather is right. I have about 30 flats out there now and several have already sprouted. (My asclepias tuberosa sprouted today!!!!)
One advantage of rigid polycarbonate over glass is that hail cannot break the poly . Do you think that glass will take hail ???? It really depends on how often the threat of hail enters the equation . It has happened 3X over the last 2 years in our area so I would avoid glass here . Whatever you do , I guarantee that you will love your coldframe / greenhouse :))