frequently asked questions about radiant barrier foil insulation 1) How Does Radiant Barrier Foil Insulation Work? 2) How Can Radiant Barrier Keep Heat Out Of My Home In The Summer? 3) How Can Radiant Barrier Keep My Home Warm In The Winter? 4) What Is The "R" Value of Radiant Barrier? 5) I Have Adequate Insulation In My Attic Now. Do I Really Need Radiant Barrier? 6) Do I Have To Remove My Existing Insulation To Install The Radiant Barrier? 7) Will the aluminum corrode and lose it's effectiveness? 8) Will attic dust hurt the reflectivity and performance of the radiant barrier? 1) How Does Radiant Barrier Foil Insulation Work? Radiant barrier foil insulation is unlike mass insulation that only slows down or resists heat transfer. Radiant barrier foil insulation reflects heat. Heat always goes cold by natural law - the problem is how to keep the heat in the winter and how to keep it out in the summer. There are 3 ways in which heat goes from warm spaces to cold spaces: CONDUCTION - Which is direct heat flow through a solid object such as a wall or ceiling. CONVECTION - Which is heat movement through air, occurring when air is warmed. The warm expands, becoming less dense and rising. RADIATION - Which is the movement of heat rays across air spaces from one warm object to a cooler object. The heat we feel from a wood stove or a space heater is radiant heat. All objects and bodies give off radiant heat. Even the insulation in your attic gives off radiant heat to the cold attic space in the winter and to the living space in the summer. Conventional insulation will not store radiant heat loss. Radiant heat must be reflected with a radiant barrier. 2) How Can Radiant Barrier Keep Heat Out Of My Home In The Summer? Just like a space suit, radiant barrier reflects the sun's heat before it can warm up the insulation in your attic. When the insulation stays cooler, your home will stay cooler. It helps to understand how radiant barrier works for you if you think of other things that work in much the same way. Astronauts Space Suits - keep body heat, and reflect the sun's heat away. Thermos Bottles - keep hot things hot and cold things cold. They are almost perfect insulators. The tight seal and air space prohibits heat transfer by conduction and convection. If the bottle starts out hot, it stays hot because very little heat is transferred to the cooler outside. If it starts out cold, it stays cold because very little heat is transferred from the warmer outside. 3) How Can Radiant Barrier Keep My Home Warm In The Winter? When you cover your attic insulation with radiant barrier insulation it will hold the heat in your home. For example, if you wrap a potato in aluminum foil and bake it, the potatato will stay warmer much longer than if you had no foil around it. 4) What Is The "R" Value of Radiant Barrier? Radiant barriers do not absorb heat. Instead, they reflect up to 97% of the heat that hits it and therefore, have no R-value rating. Installing a radiant barrier between the heat source (sun) and an existing R-value rated insulation will improve the effectiveness of the R-value rated insulation. The reason being is because only 3% of the heat is now hitting the R-value rated insulation, therefore it will take longer for it to absorb 100% of it's potential thereby holding the heat longer before passing out the backside into living spaces. 5) I Have Adequate Insulation In My Attic Now. Do I Really Need Radiant Barrier? "A radiant barrier system can stop 97% of the thermal radiation across an attic space. If it is not stopped, that radiation energy would be absorbed by the ceiling insulation and eventually be transfered to the living space below." "The Solar Collector," Quarterly Newsletter of the Florida Solar Energy Center. "The heat storage capacity of reflective insulation is low. As a result, it does not store heat during summer days, only to pass it on down into the rooms of the house from the attic at night when coolness is most apt to be desired from the point of view of sleeping comfort." "Progressive Architecture," Nov. 1949, Page 76. WINTER: "CONCLUSIONS: Reflective foil retrofitted to fiberglass insulated buildings is demonstrably effective in reducing heat loss. Installation of foil in uninsulated buildings would show even more pronounced reduction in heat loss." "Effects of Reflective Foil On Heat Loss in Attic Floors and Metal Building Installations," Northeastern Illinois University, Prof. Charles Shabica, May 20, 1986. 6) Do I Have To Remove My Existing Insulation To Install The Radiant Barrier? No. Radiant barrier will actually help your existing insulation to be much more effective. 7) Will the aluminum corrode and lose it's effectiveness? "Hundreds of samples of aluminum foil have been stored in the laboratory for various periods of time up to 10 years with no visible signs of deteriation." American Society of Heating & Air Conditioning Engineers' Journal Section." "Aluminum is highly resistant to the effect of corrosion....Aluminum is constantly being used where it is exposed to weather, salt spray and other conditions, which would adversely affect most metals." The United States Rubber Co. Booklet, "Serving You Through Science." Page 5. 8) Will attic dust hurt the reflectivity and performance of the radiant barrier? No. An exhaustive test performed by James R. Hall, project engineer for the Tennesse Valley Authority concluded that "...the dust appeared to have little effect on the effectiveness of the radiant barrier. The percent reduction in ceiling heat flux was remarkably similar to that of a radiant barrier with no dust." "Thin layers of dust readily visible to the eye do not cause very serious lowering in the reflective power. The appearance of the surface is not a reliable guide as to it's reflectivity for radiant heat, and foil which appears dark or discolored may have lost little in insulating value if the surface film is thin." U.S. Dept. of Commerce, Letter Circular - 535.