I'm in zone 4/5 and my GH is single pane. I checked out double pane for the insulation value, but the cost was way too much for me. In addition to the glass itself, the weight is significantly heavier so the GH structure needs to be sturdier, which also adds costs.

If you are building the GH yourself and plan to frame it with lumber, the weight of double panes shouldn't be an issue and in an area that experiences mild winters but very hot summers, insulation is as important as it is where winters get bitterly cold.

In fact, it's a lot easier to keep a GH warm in winter than it is to prevent it from becoming an oven in summer and the plants will grow as well under double panes as they do single.

Thanks! You both have given me a few things to think about. The frame base will be the frame of this shed, with a few modifications:

{{gwi:296433}}

One thing I did not mention in my original post was that I don't really plan to run electricity out to the greenhouse - will that make a difference in the pros/cons of single or double?

Build it with what you have. Single should be fine for you. Look into heat-activated, non-electric, pneumatic openers. I think I saw that the Chinese Consulate, um, I mean Harbor Freight has them for about $20. There are also solar powered attic vent fans available at places like Home Depot for a bit more. If you go with single but find that you want more heat retention in the winter, look into preventing heat loss by air infiltration through small gaps in the walls and around the door and windows, insulate your north, east, and west walls, and consider temporary plastic over the windows to raise their R-value.

I assume that in the heat of the summer you'll be leaving the place empty.

Double pane windows are only good for 5-7 years and then they start to fog up thats crap, i have double pane insulated glass it will last longer than that. 30 years and more. i make custom entry doors and if i had to replace glass that often i would be out of buisness.