Installing Radiant Barrier Insulation
There are several ways that radiant barriers can be installed in both an existing home and a new build. All radiant barriers have at least one low emissivity (reflective) surface, which is either in the form of a sheet or a coating of aluminum. Emissivity is expressed in a value of 0 - 1. It is compared to an opaque material, which has no reflectivity. A foil barrier panel should have an approximate value of 0.9, or a reflectivity of 90 percent. The reflective panel must face an open air space to function properly.
Obviously the most proficient method of installation would be in a new home build, but even an existing home is not hard to retrofit. In the basic application, sheets of radiant barrier are placed over the existing insulation in the attic. This is called an attic floor installation. Generally, they are overlapped, and are not stapled in, allowing access to wiring that might require work. Care must be taken during installation to insure that the reflective side is facing up, and that the radiant barrier does not actually touch the insulation. This is to insure that a dead air space is present. If the aluminum sheets are laid on touching the insulation, the radiant barrier will transfer heat to the insulation, thus allowing heat to enter the home during the summer and escape in winter.
Another way to install a radiant barrier is to attach the foil sheets nearer to the roof. Several methods are used to accomplish this. In a new home build, one method is to drape the foil sheets over rafters before the roof decking is installed. Another method is to attach the radiant barrier to the bottom of the roof deck. In a retrofit, this type of installation would be accomplished by attaching the foil sheets to the undersides of the rafters, allowing for at least a 3/4 inch dead air space.
A third type of radiant barrier installation is to place the barrier in the walls of the home. This is best done in a new build, or during a full retrofit in an existing home. To accomplish this, the installer sets firring strips around the wall perimeter, which separates the outer wall from the external wall structure, and "sandwiches" the radiant barrier between the outer and inner wall. The radiant barrier is always installed with the reflective side facing the vented air space. A system of vents at the top and bottom of the interior wall is used to direct the heated air upwards into the attic, where it is dissipated through the attic venting system.
A major consideration in any radiant barrier installation is to insure that the attic of the home is properly ventilated. The attic must breathe to prevent water vapor from forming beneath the radiant barrier. Water vapor from the living space can condense and freeze in colder climates and can lead to disastrous results in ceilings if there is no method in place to insure that the water vapor is expelled from the attic. Many new constructions use a system of vented soffits and vented roof peaks that insure proper air flow in the attic.
In existing homes without this system in place, an attic fan can be installed to insure that this problem is taken care of. Many of the manufacturers of radiant heat barriers today have a series of perforations built into the panels to insure proper breathing of the air space, and some types have a substrate that naturally allows water vapor to be expelled without making holes in the foil panels.
Radiant Barriers Lead to Energy Savings
What are the savings to the homeowner if a radiant barrier installation is considered in either their new build or in an existing home? According to the Florida Solar Energy Center, a proper installation of the radiant barrier can improve the thermal integrity of attic space. An installation of a radiant barrier with an R value of 19 is more efficient than a typical R-30 insulation application. This significantly lowers energy costs over a typical heating or cooling season.
The FSEC reports that a 16 percent reduction in peak demand for energy was accomplished on test sites during a typical summer cooling season. And even better results and savings can be had by adding more insulation to the home along with the radiant barrier system. The Tennessee Valley Authority confirms this with studies that show combining a radiant barrier with R-11 insulation is as efficient as an R-19 insulation installation. They also confirm that adding a radiant barrier to an R-19 insulation package has the same effect as a stand alone R-30 insulation installation. The Reflective Insulation Manufacturers Association (RIMA) reports a energy savings of 10-30 percent in a typical home with R-19 insulation and a radiant barrier system, depending on placement and type of application.
Radiant barriers are a great way to provide energy savings, and improve the comfort level of your home. Although cost of installation varies from manufacturer to manufacturer, and from locale to locale, the average costs for installation and materials runs from 12 cents to 35 cents per square foot. Considering the savings in energy bills during a typical heating or cooling season, the cost of installation is well worth the investment.