I'm personally a big fan of melamine for homemade cages which I've built two of. You don't have to worry about sealing the surface area, just the seams (silicone caulking does the trick nicely). The larger of the two is for my 13' adult female burm (cage dimensions 8'L X 2'H X 2'D). The multi-cage unit I built houses some of my boas and my juvenile burm (4'T overall X 4'W with each unit being 11"H and the top unit being split into two smaller 2' X 2' cages). For the average burm, the dimensions of the cage in the multi-cage unit won't work for long (4'L X 2'D X 11"H) but my albino girl has got to be the only finicky eating burm and is only about 5' at almost two years of age (I can't stress enough that by no means expect this with the average burm - this one is just an odd duck in the burm world).
As for the cages, the large one has a vent which is what her CHE rests on and that provides enough air flow around it. With the new multi-cage unit, I am having to go back in and add some small vents as the plexi doors fog over from the humidity (will probably be doing that tonight). Those are heated using Ultratherm heat mats, which I am really pleased with. Do keep in mind that if you go with the Ultratherm heat mats (which are placed INSIDE wooden cages), you will need a thermostat to prevent overheating because the wood insulated it well and causes the temperatures to reach a 100F or just over.
Here's a pic of the multi-unit cage:

For some reason I can't get the large cage pic to load right now - I'll post a pic of it, too, when I get it to work. 
Raven