Answer: Painting the inside frame of your greenhouse white will certainly help reflect light back into your greenhouse. I don't think insulation is necessary in your gardening region, unless you are growing tropical or subtropical plants. Most people have what they call a cool greenhouse where temperatures remain above 40F in the wintertime, which is quite pleasant for most plants. I think your biggest concern will be ventilation and lighting for your plants and there are lots of home greenhouse books and manuals that you might want to check out at your local library. In my own case, trial and error has been a much better teacher than anything I've ever read! Best wishes with your greenhouse!
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