Reflective insulation systems are fabricated from aluminum foils with a variety of backings such as kraft paper, plastic film, polyethylene bubbles, or cardboardThe resistance to heat flow depends on the heat flow direction, and this type of insulation is most effective in reducing downward heat flowReflective systems are typically located between roof rafters, floor joists, or wall studsIf a single reflective surface is used alone and faces an open space, such as an attic, it is called a radiant barrierRadiant barriers are installed in buildings to reduce summer heat gain and winter heat lossIn new buildings, you can select foil-faced wood products for your roof sheathing (installed with the foil facing down into the attic) or other locations to provide the radiant barrier as an integral part of the structureFor existing buildings, the radiant barrier is typically fastened across the bottom of joists, as shown in this drawingAll radiant barriers must have a low emittance (0.1 or less) and high reflectance (0.9 or more).
