A house can be threatened by a wildfire in three ways: direct exposure to flames, radiated heat, and airborne firebrands (burning embers). Of these, firebrands account for the majority of homes burned by wildfire. The most vulnerable part of a house to firebrands is the roof. Becaue of its angle, the roof can catch and trap firebrands. If the roof is constructed of combustible materials such as untreated wood shakes and shingles, the house is in jeapordy of igniting and burning. Not only are combusitble roofing materials a hazard to the structure on which they are installed, but also to other houses in the vacinity. Burning wood shakes, for example, can become firebrands, be lifted from the burning roof, carried blocks away, and land in receptive fuel beds such as other combustible roofs. Unfortunately for homeowners with existing combstible roofs, there are no reliable long-term measures available to reduce roof vulnerability to wildfire other than re-roofing with fire resistant materials.