Some commercial boxes staple screening to the inside of the box which may eventually fall off. Roofs without shingles may last only a few seasons, once the roof is compromised the box will be incapable of retaining heat and fall into disuse. Nailed together with unsealed seams. This type of box will warp and separate at the seams allowing unwanted ventilation and disuse. Unpainted, unprotected exterior.
Some manufacturers insist on leaving bat boxes unpainted.
While in certain regions the natural wood color may be a suitable color, there is no good reason for the structure to go unprotected. Bat research has proceeded at a very fast rate, thanks to improved communication among many different hobbiests and researchers. For example, a tall open-bottomed bat house is now prefered over smaller closed bottom designs which tend to attract more parasites. Bat house plans can be found in a variety of places, which is good. Unfortunately, many posters, books, and flyers were published years ago with now antiquated plans.