You should consider design when selecting your bat house. All landing areas and interior surfaces should be rough, such as natural cedar, to allow bats to easily cling when landing and roosting. Ventilation gaps are integral to maintaining suitable bat house temperatures. According to research, larger bat houses (multi-chamber or "nursery" houses) have higher occupancy rates than single chamber houses. Most North American bats prefer to live in large groups, called colonies, so a house that can hold at least 300 bats is typically recommended. An alternative approach is to combine a larger house for the females and their pups, and a smaller house for the more solitary males, which can establish larger and more stable bat colonies.