Hi all, im a newcomer to the greenhouse community and was looking for some help. I live in chicago and it gets really cold so I need a way to keep my greenhouse warm. I have a hoop house made of pvc pipe and some railroad ties. I was thinking of using two layers of plastic during the winter, but I did not want to buy a blower because at the moment I cannot afford one. My question is, can I still use double layer if the layers are separated without a blower. I was going to leave about 2-3 inch of space between the two and was wondering if that would keep the warm air in. All help is welcome and appreciated. I was also considering using one layer of plastic and then I would insulate it with bubble wrap. Any thoughts on this.