Hi, I recently ordered a sub adult hognose and for Her setup I was planning on using a 20 gal glass terrarium. I would use a tub but I'd love to see this tank get used. My state has very cold winters, so I decided to wrap the terrarium's screen lid with plastic to help keep in the heat provided by the UTH. The problem is that I'm afraid this will cut off air circulation. Is there another way to trap heat or will this be ok?