When I built my new house a couple years ago, one of the main reasons that we built was so I could have a snake room that was not attached directly to the main part of the house. The wife did not want the AC in the snake room to be part of the rest of the house AC. I decided to go with a three car garage and made the single door garage into the snake room. I had the builder add extra electrical outlets, a utility sink with hot and cold water. I built the wall between the two car section and the Snake Room section and insulated the wall. In the wall I made a door so I could keep it closed off. I put in a separate Light/fan for the room and then I had to tackle the problem of keeping the room cool, not cold but cool enough that during the summer months here in FL where it is 98 degrees outside, I could keep the room down to about 80ish, maybe crank it down to 76 if I was working out in the room.
I went to home depot and they sell a stand alone, non-wall mount AC unit that blows exhaust out a dryer vent, it was perfect for what I needed. It covered my whole 10x22 foot snake room with no problems and with the $5.00 dryer vent added into the wall, it works perfect.
No some advice and some spots that I hit and had to correct that I will let you in on. The garage door, if you have a garage door, as I do in my snake room it is helpful on nice days to open it up and let the natural air in, but make sure the snake are all securely in their cages. Also the garage door will need to be insulated, it lets in heat and or cold like crazy and some insulated boards from Home Depot helps with that. You can cut them into size to fit into the garage door panels.
A window for natural light would have been nice, but I did not think about it in time and really have no plans on knocking down the cement wall to do so.
Insulate the attic above the garage to save a lot of heat loss and when you are all done, you should have a good place to keep your snakes with out offending guests or having the wife complain about the odor.
Good luck
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Jim Hopkins "Hoppy"
Hopkins Holesale Herps
Hopfam1@aol.com