Today I put up the Bat House I built last year. It's cedar and has 3 chambers. Multi-chambered houses are like apartment buildings, so there is potential to get more occupants. (They pay their rent in eating mosquitoes and producing guano.) According to various websites, the house should be mounted over 15 feet high on a wall or chimney which gets at least 8 hours of sunlight. Bats definitely don't want their homes to be in trees. I suppose they consider it inferior territory for the likes of birds and squirrels. This was the best I could do on our house which is in a heavily wooded area.
As of this writing, I have learned that mounting on aluminum siding - as was done here - was not a good idea and such a location will "rarely be used". I'm better off putting it on a pole. Now where do I find a 15 foot pole?