Cooling Energy Measurements of Houses with Attics Containing Radiant Barriers

Abstract

Tests were conducted by Oak Ridge National Laboratory (ORNL) to determine the magnitude of the energy savings brought about by installing radiant barriers in the attics of single-family houses. The radiant barrier used for this test was a product with two reflective aluminum surfaces on a kraft paper base. The radiant barrier has the potential to reduce the radiant heat transfer component impinging on the fiberglass attic insulation. Working as a system in conjunction with an air space, the radiant barrier could theoretically block up to 95% of far-infrared radiation heat transfer. The experiment was conducted in three unoccupied research houses that are operated by ORNL. One house was used as the control house (no barrier was installed), while the other two were used to test the two different methods for installing the radiant barriers. In one house, the barrier was laid on top of the attic fiberglass batt insulation, and in the other house, the barrier was attached to the underside of the roof trusses. The attics of all three houses were insulated with kraft paper faced nominal R-19 fiberglass batt insulation. The results showed a savings in the cooling loads of 21% when the radiant barrier was laid on top of the attic fiberglass insulation and 13% with the radiant barrier attached to the underside of the roof trusses. The savings in electrical consumption was 17% and 9%, respectively. The electrical consumption data and the cooling load data indicated that the most effective way of installing the foil was to lay it on top of the fiberglass batt insulation. The radiant barriers reduced the measured peak ceiling heat fluxes by 39% for the case where the barrier was laid on top of the attic fiberglass insulation. The radiant barrier reduced the integrated heat flows from the attic to house by approximately 30-35% over a 7-day time period.