Winter is creeping up and it is cold outside and inside my house. I have no heat and a separate space heater is not an option. Right now it is 60 deg inside my house.

It is 92 deg on the warm side of the tank, belly heat. Ambient temperature on warm side is 75 deg and 65 on the cold side. Humidity is 52%. I have a heat lamp on the warm side right now.

I read that putting foam insulation boards around the outside of the tank work well but I have no money to purchase them. Would using cardboard instead help keep the cold out? I have lots of cardboard.