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Cold frames - Plastic or glass?

I am going to be making several cold frames for use this spring. I have several old storm window panes of glass that are the perfect size for the cold-frames that I want to make.

My question: should I forget the glass and use the clear plastic sheets, or will glass actually be a good choice for a cold frame?


(Zone 5a)

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.


Richmond, KY(Zone 6b)

Hey, Dave,

If you decide to go with plastic I'll be glad to drive down and take those window panes off your hands.

Glass is really the best medium. Plastic is used because it is more readily available and cheaper. I assume you mean plastic film, rather than rigid stuff?

You could get away with the film, but, personally, I wouldn't use it in high-snow areas.

Polycarbonate sheets run glass a close second. But they can be pretty expensive if you are building several frames.

The long and the short of it, however, is this. You already have the best material going. Why use something else?

These were the answers I was hoping for and expecting. I can't wait to build my cold-frames.

PS Brook: I was talking about the plastic film. I saw it in a cold-frame building HOWTO once... Glad to hear that glass is preferred - that made sense to me.

I've got around ten 3'x1.5' panes. My barn is full of raw materials. :)


Bay City, MI(Zone 6a)

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.

(Zone 7a)

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!!!!)

Lyndeborough, NH


I prefer glass over plastic for many reasons.

#1 being the transmission of UV and IR radiation.


Chatham-Kent, ON(Zone 6a)

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 :))

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