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Radiant Barrier
What is radiant barrier? Radiant barrier is most commonly known as a reflective insulation used to lower attic temperatures. According to Energy Star radiant barrier must reflect at least 90% of the radiant heat and have an emissivity of no more than 10%. The most common types of radiant barriers in the market today are foil backed insulations and metalized film radiant barriers. Radiant barrier paint and spray on radiant barriers are too often mislabeled as radiant barriers when they are in fact IRCC's (Interior Radiation Control Coats). Comparing the two is like comparing apples and oranges. IRCC's work best when they are installed on something that they can reflect direct sunlight off of, such as armored vehicles or on top of commercial buildings with flat top roofs for example. Its important to understand that by definition a radiant barrier must have an air space to reflect heat otherwise its working off the emissivity value of the product. When IRCC's or radiant barriers are installed on the underside of the decking the only reflective surface they have is the one facing the inside of the attic. So in these applications they are limited to working with their emissivity value with the heat coming in from the roof and not their reflective value. Radiant barriers for attics perform best when insulating attic rafters or installing the radiant barrier over the attic floor (See Radiant Barrier Installation for more details). These installation methods provide the airspace needed for the radiant barrier to perform as a reflective radiant barrier. Understanding these key principles is the first step in understanding what a radiant barrier is.
Does Radiant Barrier Work?Attic radiant barriers work exceptionally well at cooling the attic when they are used to insulate attic rafters. Radiant barrier installed to the underside of the rafters allows for an air space between the roof deck and the topside of the radiant barrier. The hot air can then be channeled in between each rafter cavity to the roof top vents without ever entering into the attic. Radiant barrier effectiveness is directly correlated to the ventilation in the attic where it is installed. Many people have claimed that radiant barrier didn't work for them. But when questioned, their ventilation was not properly matted for the type of radiant barrier installation they had. Radiant barrier can also be installed overtop of the attic floor. Depending on the r value of the insulation and the attic ventilation, installing radiant barrier directly over the insulation can be very cost effective.
Foil Backed InsulationReflective attic insulation is typically a foil faced insulation or a metalized film. There are several different kinds of reflective insulations available on the market. Foil faced fiberglass insulation is simply fiberglass insulation in between two layers of aluminum film (We call it FiberCore™). Double bubble radiant barrier is encapsulated air pockets sandwiched in between two layers of highly reflective metalized film (We call it DoubleCore™). Foil faced foam insulation is closed cell foam insulation in between two layers of aluminum film (We call it FoamCore™). Foil faced foam is available in different thicknesses as well as perforated and non-perforated. Perforated "no tear" radiant barriers have a woven polyethylene scrim in between either 2 layers of foil or highly reflective metalized film (We call it PolyCore™). HeatBlockers does NOT install the "no tear" FOIL style radiant barriers because they do NOT meet the current fire codes in the U.S. While all of these reflective insulations perform similar to each other they have distinct differences. It's The Core That Makes The Difference™.
Radiant Barrier vs. InsulationRadiant Barrier Paint vs Foil would be a much better vs than radiant barrier and insulation. Convention insulation whether fiberglass, fiberwool, rockwool, or cellulose all work with conductive and convective heat. They work by slowing heat transfer down. Radiant barriers on the other hand work with radiant heat. Instead of slowing heat transfer down they simply reflect the heat away. Simple put as the radiant barrier reflects the heat the ventilation pulls the heat out resulting in less heat being absorbed into the insulation. The ventilation serves a double purpose in the fact that it not only pulls out the heat reflected by the radiant barrier but it also pulls out the moisture in the attic keeping the insulation dry. It's a system approach that has to be taken when making an attic efficient. The first place to start is with proper attic ventilation, then insulation, and finally a radiant barrier.
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