Many local history museums cannot simply block up all their windows because they occupy historic buildings. As a further step, close all blinds, drapes, or shades when the museum is closed or when a particular room is not in use. If you have police patrols that prefer to see in windows, make covers for cases, furniture, and mannequins to block sunlight when the museum is not in use. Cloth covers should be made of white sheets, white flannel, or unbleached muslin to avoid heat build-up. Blocking the intensity of daylight is followed in priority by limiting the length of exposure to all light sources.
Temporary exhibits are an ally.
Objects that are not currently on exhibit can be kept in darkened storage rooms and cabinets. Changing the objects on exhibit will extend their life accordingly. If you have a sunny and cheerful room, put your office not your exhibits there. Plan long-term exhibits in the areas with the lowest amount of daylight. Never put wood pulp paper, fabrics, colored prints, or watercolors on permanent exhibit.