Another thought on this is condensation. If that big wad of plastic is cold, cold, condensation will develope between the Pyrex and the plastic. That can get nasty. I am really new to all of this, but I also live in an area where the cold brings on a lot of unusual things. Up here in the ice box we get accustomed to the affects that the cold has on things. My advise is to store the plastic and the components inside where its heated until youare ready to use them. I have MY closet and keep it all in there.
Not bad here today. 33 degree high, broken sun on fresh over-night snow. Sound like a postcard? Trust me....it sucks. I like the 80's and about 70% humidity, no wind and my butt in the boat.