Radiant Wall and Attic Barriers - Reflective Insulation
No matter how efficient a heating or cooling method may be, it's only going to be effective if a home is well insulated against energy loss. The process of hot and cold air escaping through walls, windows and ceilings has traditionally been slowed by conventional fiberglass insulation, but with the advent of the radiant barrier, desired temperatures can now be further locked in.
A radiant barrier is not much more than a thin sheeting of highly reflective coating or foil, usually aluminum. This is stretched out or glued to paper, cardboard, or some other type of material giving the barrier enough structure to be placed where it needs to be. Radiant barriers can also exist in the form of liquid coatings, paints, sheathing, or even reflective roofing shingles.
Radiant barriers are reflective, and not insulating. They are meant to used in conjunction with home insulation and not in placement of it. Although the shiny surface may seem designed to bounce and reflect light, radiant barrier insulation works to reduce thermal heat radiation by transferring it back against its source. For example, when the sun heats up a roof and thermal radiation penetrates into the attic, a radiant barrier will reflect much of that heat back toward the roof again. The more the barrier is placed at an angle perpendicular to the temperature source, the greater the reflectivity. This makes radiant insulation techniques ideal for lining the insides of attics along the inside of the roof structure. Radiant barriers have high reflectivity, allowing for maximum heat and cold deflection. At the same they have low emissivity, meaning they emit the lowest possible amounts of heat radiation transferred across their surfaces.
|The installation of a simple radiant barrier in your attic can save you between 10 and 15% on your heating and cooling bills, depending upon the climate in which you live (with hotter climes having more savings).|
Applications for Radiant Barriers Within the Home
Radiant barrier systems are most commonly installed along the inside of an attic's roof, although foil barriers are also installed along the attic floor as well. Care must be taken when doing this however - water vapor must be allowed to still pass through or condensation could become a problem. In some cases radiant foil can be installed straight onto roof sheathing, or rolled out across the plywood before the shingles are applied. Specialized radiant roofing exists for this purpose as well.
As green building techniques become better promoted, radiant barriers have also been used to line the walls of homes. Pipes and water heating equipment can be lined with foil barrier products designed solely for this purpose. Some products can act as vapor barriers, preventing the moisture from passing through its surface. The reflective surface must be properly installed here, and products with small perforations to allow moisture through are available.
Generally, the warmer the climate in which you live, the greater the energy savings will be realized when installing a radiant barrier. Centrally air-conditioned homes carrying a lot of ductwork in the attic can see substantial savings in cooling bills due to big reductions in attic temperature. In cooler areas, these barriers will still trap heat inside the home and lead to somewhat less heating costs as well.
Foil barrier products can also be purchased in large rolls. Either one or two sided, this type of reflective foil is usually a standard width of 4 feet and may contain bubbles of air trapped between the two surfaces for added insulation. In double bubble foil, two layers of bubbles are laminated between the reflective film.
Commercial radiant projects may require a foil with a much higher reflective factor, and also a material that is vapor retardant. Companys such as Tempshield™ make foil barriers that can reflect up to 95% or more of all radiant heat striking its surface. The same foil's properties of low emissivity boast a re-radiation percentage of only 3% or less.
Such material can be cut and shaped to create heat jackets for hot water heaters and other plumbing equipment. Up to 20% of hot water heating costs can be recouped each month with the right barrier application.