Temperatures below freezing will not kill mould, but they do make it dormant. In conjunction with humidity and temperature control, adequate air circulation will help prevent mould growth. Air circulation helps control moisture levels through evaporation. Light Sunlight, and in particular ultra-violet radiation, generally inhibits mould growth. Chemical composition Mould growth can also be affected by the chemical composition of the book or paper food source.
Many fungi prefer slightly acidic material.
There are several modifications that can be made to a building or its internal environment which will assist in preventing mould outbreaks. Don't shelve books directly against an outside wall. Due to temperature and humidity differences between inside and outside environments, moisture may develop along walls. Allowing air to circulate against the walls will enable the moisture to evaporate. Keep the quantity of indoor plants to a minimum.