Glee Skals

Thanks for the reply mike. I've been working on all kinds of methods to cover the glazing at night and I'm finding out why there isn't any real info about how to do it, because it's not an easy thing to have something moveable with a high r value.  When you think about insulating the north, east, west walls to an average r value of say 24  then have half the structure (the glazing) at r2 the high r walls are not saving all that much. Increasing there r value is not cost effective above a minimum without also addressing the glazing heat loss. Now if we could get that glazing to r24  at night then  storing solar heat in the floor, or water ,or even heating the greenhouse become a real asset for cold winter growing in our zone.

I haven't come up with any way to do that yet, at least not if I want a conventional looking greenhouse but I'll continue  thinking it thru.

I Wasn't suggesting you put polycarbonate on your greenhouse just that I had thought of a similar idea but had thought about the polycarbonate because I live where its windy all the time and plastic just wont hold up. I do think though it might help to allow your insulation to endure the rigors of repeated opening and closings. Maybe one day when you have to change it for some other reason

Ill keep following this thread and see how it turns out for you and if I come up with a way to get that r24 glazing covered at night ill share it.

Enjoyed reading your adventure in building your greenhouse. I'm also designing a greenhouse for zone 4 and have been studying the various ways to keep low temps above 50f with sub zero winter temps.
It seems from studying the available info on the web  a lot of effort  and thinking goes into finding ways to store or add heat during night time lows and not much thought goes into addressing the elephant in the room ,the huge heat loss thru the glazing at night. I was glad to see you at least have attempted to minimize this.
I'm assuming since the snow is pushing the poly layers together it's not easy to get the rolled insulation to fall down. I had a similar idea but instead of poly id use two layers of polycarbonate with a high r  value rollup blanket in between them. Have you tested to see if your insulation has an effect on inside temps when it's deployed? I'm assuming it has an r value around 4. Is that about close?