The amount of ventilation required will vary with several environmental conditions. Everything from the size and location of the water bowl you use to the ambient temperatures and humidities in your home will contribute to how much ventilation is required. This is not something that you can plug into a formula and get an answer. You need to monitor your cages and specimens and adjust accordingly.
My philosophy is to install excessive ventilation and then cover it to reduce ventilation as necessary. I find it easier to cover it than to add more later. Especially if the humidities in your home vary greatly throughout the year. I highly recommend you do this.
Furthermore, if it is cold in your home heating the entire cage with just flexwatt may be difficult.
I don't know what material you plan to use, but I'd recommend that you at least cover the floor with PVCX (aka expanded PVC), the same material used by Boaphile and Moonstruck, to name a couple.
If your cages are built from melamine or plywood, you can cut a large section of the floor out without comprimising the structural integrity of the cage. Then cover the entire floor, not just the cut out area, with a sheet of PVCX. The flexwatt will go underneath this floor in the cutout area.
The PVC material will not only be easy to clean and tolerant of urates, moisture, etc., but will also conduct heat nicely due to the closed cell nature of the foamed interior.
***************
I am planing on building a multi compartment enclosure for a few corn snakes, and one boa, I am wondering how much ventalation I need to put in it. I am planing on useing flexwatt for the main heating element and I am worried because i live in a cold climate and i do not really heat my house very much and if I have to many vents I am afraid that it will get too cold in the enclosure. I want to know what i really need to keep my snakes healthy. I dont have a seperate room that I can heat by itself and keep them in. I am looking at all these chage designs that have these huge vents and if i do that I am pretty sure my snakes will freeze,
Do the vents need to be different for the boa then for the corns or will the same setup work for both with just a bigger area for the boa. I was thinking about makeing the setup 6 feet long 2 feet deep and 2 feet high 6'*2'*2' for the boa with a shelf, and smaller two feet wide and deep by 1 foot high 2'*2'*1' enclosures for the corns, would that work well? and what type of venting dose each one need?
