Different types of insulation protect against different kinds of heat. Radiant barriers deflect radiant heat, which can pass through other types of insulation, to further increase your home’s energy efficiency. Radiant barriers are installed in homes -- usually in attics -- primarily to reduce summer heat gain and reduce cooling costs. The barriers consist of a highly reflective material that reflects radiant heat rather than absorbing it. They don't, however, reduce heat conduction like thermal insulation materials.