You can run them in a shed no problem, the heat will warm up and dry up the place. Prepare a plan where you can heat up the place BEFORE starting up the miner, IE do not start the miner at -20 C
1 miner might not be enough to warm however. might need 4 hehe.
Did some one already had this kind of problem ? It's the first time I hear that miners need a minimum of heat (usually people want the coldest place for their miners so they can overclock/overvolt them).