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Solar Radiant Heat
In summer, heat travels through your attic primarily as radiant energy, rather than by conduction or convection. The sun radiates heat to the roof surface-as high as 190◦ on a black roof. With a roof made of organic material, such as composition shingles, the heat conducts through the underside of the roof deck and from there radiates down to the top of the ceiling insulation. The heat then conducts and radiates into the room below. Place a radiant barrier (e.g, metal roof) between the sun and the ceiling insulation and you break the chain. The heat can no longer radiate down through the attic and is stopped dead in its tracks. A clean, shiny radiant barrier reflects 97% of the radiant heat back up into the outside air.
A shiny surface will neither absorb nor emit heat very well. This is the reason that you may have to touch a household iron to see if it is hot enough to iron clothes, even though the iron uses the same amount of energy as an electric heater that can heat the entire room.
Up to 97% of the sun’s rays are reflected with a Metal Roof radiant barrier.
The sun’s radiant heat rays penetrate right through all of the organic material. This is the reason you may feel hot on a sunny day and cool on a cloudy day, even when you are in an air conditioned building and the temperature has not changed. Just like a microwave oven heats food through a plastic container but will not heat the food through a can or aluminum foil. (radiant barrier)
The Attic air (which is heated convectively by the ceiling insulation and radiantly by the roof deck) stays cooler with a Metal Roof Radiant Barrier.
A METAL ROOF consists of Stone Coated Steel Shingles or Standing Seam Panels
AN ORGANIC ROOF consists of Composition Fiberglass, Wood Fiber Cement, or Concrete Tile
IN BRIEF…
Without a radiant barrier: The Sun radiates heat to the roof, the roof deck, the attic insulation and to anyone inside the home.
With a radiant barrier: 97% of the heat is reflected off the metal roof radiant barrier, preventing heat from radiating into the home.
TERMS:
Conduction:
the conveying of heat through an object. |