How to heat an enclosure?

[msubigdawg]

I built an enclosure for my Brazilian Rainbow Boa. The humidity and everything is fine its just the temp. The enclosure is 4 feet long, 2 feet tall, and 2 feet deep. The top is plexy glass and the front is plexy glass. The back, bottom and sides are 3/4 inch plywood. I have a radiant heat panel attached to one of the inside walls but the problem is that it won't heat the enclosure right. All the heat raises to the top of the enclosure and none on the bottom. I would put it underneath but I do not think it will heat through the wood because of the thickness. I bought just a regular human heat pad for the inside, I think I will attach that to a rehostat or thermostat unless someone has a better idea of how to heat this enclosure. I am trying to stay away from using a heat lamp. I would really appreciate any help.