Mike Jay wrote:Thanks Jim! It's one layer of 2" foam that is 8-12" deep at the foundation, sloping down to probably 12-16" deep 3' away from the foundation. I considered doing 4" of foam but found (or someone found for me) some data showing minimal benefit from the additional thickness.
Mike Jay wrote:I got the moveable insulation about half deployed and we'll see how that helps overnight. Should be around -30F tonight.
I'm not sure the perfect answer for your endwall question. I think it depends on your goals for the greenhouse. If you're going to try to keep it warm through the winter at our latitudes, I think they have to be insulated. I'd only get a bit of light (and solar heat) through them for an hour a day. Then I'd bleed heat out through them for 23 hours a day. If you are just going for a much longer growing season, glazing part of them might start to make more sense. Maybe glaze the south half of each and insulate the north half. Another way to think of it is that at 10am the sun is hitting the outside of the E wall and not entering the greenhouse. But the sun that goes into the greenhouse and hits the solid W wall is reflected back towards the plants. If those endwalls were clear, that 10am sun would enter the E wall but the sun going through the greenhouse and hitting the W wall would escape and light up the snow outside. So am I gaining any sun if they were clear? And keep in mind the tremendous heat loss through those walls 24/7.
Mike Jay wrote: I hope that with the compost heat working the low will be closer to 40-50 at night and 50-60 during cloudy days.