The design of a building should consider the advantages of natural light as this can reduce the cost of artificial lighting and improve the environmental performance of the building. Daylight entering the building can also help reduce heating costs. Unfortunately some stocks react badly to direct sunlight, and some stock reacts badly to extreme of temperature or may require a specific temperature for storage. Some stock may require a warmer temperature than the ambient temperature and other stocks may require cooler temperature. For example, fabric and garment are sensitive to direct sunlight as ultraviolet light catalyses a reaction between the water present in all fabrics and atmospheric oxygen to create hydrogen peroxide. This is a bleaching agent and breaks down the chemical bonds that give dyes their colour.