EPS can degrade when exposed to sunlight or temperatures over 180°F. It also must be protected from solvents, and only compatible adhesives and sealants should be used. If the insulation is to be used in the interior of a house, it needs to be covered with a fire – resistant material such as gypsum wallboard. EPS, although con­taining a flame-retardant additive, should be considered combustible and should not be exposed to an open flame or any source of ignition. Thin beadboard also can warp or chip easily, so it should not be used in high-use applications, such as movable window insulation.