The vault is approximately 12' x 16'. The humidifier drains to an outside source and does create some heat. I was in there the other day with a commercial model temp/hum. sensing device and it was 77 deg. with a relative humidity of 28%. To my mind, I thought this might be a bit dry for the wood. The metal is no problem as he keeps things oiled. I also wondered about leather items such as scabbards for his swords, etc.