I would look into building a plastic cage before a wood one. Wood can be extremely hard to heat properly and absorbs moisture much more easily than plastics even if it is coated. Have you thought about just using a tub? Temperatures and humidity is SO much easier to control in a tub and your snake will feel much more secure in a properly sized tub than in an open tank. I know everyone wants their snake on display but if you're looking for a display snake get a colubrid (corn/king/bull etc....) they're much more forgiving of temperature differences and most have almost no humidity requirements. Plus they're much more active and will be out and about 90% of the time AND they come in some really cool colors! Just an idea.