 The angled portion of the glass-support structure is opaque and well insulated with a cool roof and radiant barrier.The sawtooth roof's lighting concept partially reduces the summer "solar furnace" skylight problem, but still allows warm interior air to rise and touch the exterior roof glass in the cold winter, with significant undesirable heat transfer.Skylights are light transmitting fenestration (products filling openings in a building envelope which also includes windows, doors, etc.)