Think about what's in the room above your heirlooms, too.
Heat causes damage.
Don't hang valuable objects over radiators, heat-producing appliances or the fireplace. Books you want to read 20 years from now shouldn't be shelved on the mantle, the window sill or the radiator. Light causes fading and other damage. Don't put valuable books and paper where they'll get direct sun or bright light of any kind. Hallways or other rooms without windows are best.