(image from http://dallas.craigslist.org/ftw/pet/1059105614.html)

I saw this on craigslist, and I really like how it looks. Is it a smart design? Also, how would I keep it heated?

So, I'm guessing you would built it tight enough so the tubs would not need a lid? that's what it looks like but I'm not sure.

And, whats the best material for building? wood?