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ebuild Guide to Radiant Barrier Specifications
Insulating a building is a proven, cost-effective method for reducing heating and cooling costs. In warm climates, however, the amount of energy required to cool a building often exceeds the amount needed to heat it. In that case, additional steps can be taken to reduce cooling loads.
One of the most effective steps is to install a reflective barrier in the attic. Radiant barriers are materials that are installed in buildings to reduce summer heat gain and winter heat loss, and hence to reduce building heating and cooling energy usage. The potential benefit of attic radiant barriers is primarily in reducing air-conditioning cooling loads in warm or hot climates. Radiant barriers usually consist of a thin sheet or coating of a highly reflective material, usually aluminum, applied to one or both sides of a number of substrate materials. These substrates include kraft paper, plastic films, cardboard, plywood sheathing, and air infiltration barrier material. Some products are fiber reinforced to increase the durability and ease of handling.
Reflectance--This property governs how much radiant heat is blocked by a material, and is generally described as a percentage. The higher the percentage, the more reflective (and effective) the surface is.
Emittance--This is another measure of the efficiency of a radiant barrier. It is given as a number between 0 and 1. The lower the number, the better the radiant barrier. The most effective radiant barrier is one with high reflectance and low emissivity.
Width--Products designed to be installed between rafters or trusses come in widths to suit various on-center spacings. Products intended for horizontal installation across the roof system will be wider. Multiply the width of the product by its length to determine its coverage.
Construction type--Products for commercial construction are suited for use with masonry, steel, and other commercial construction systems. Products for residential use are optimized for wood frame construction.
Material composition--Vented radiant barriers allow moisture vapor to pass through the material. Solid barriers block moisture vapor.
Rear facing material--The rear facing material, sometimes called the backing, adds durability to the radiant barrier layer and makes it easier to handle and install.
To appreciate the role of a radiant barrier, it helps to know a little about heat transmission through a roof structure. Radiant heat travels in a straight line away from a hot material towards relatively cooler materials. In the summer, a roof absorbs a great deal of solar energy, and the underside of the sheathing radiates this heat to relatively cooler surfaces in the attic. This in turn reduces the effectiveness of attic insulation and warms air-conditioning ducts that pass through the attic, even if they are insulated. Eventually, the heat reaches rooms below the attic, making them less comfortable. A radiant barrier blocks most of the heat gain so attic temperatures remain tolerable.
Radiant barriers may be installed in various ways. The simplest way to install a radiant barrier in an attic space is to lay the barrier material directly over the existing thermal insulation, with the reflecting side facing up. A more effective method is to staple a flexible radiant barrier to the underside of the roof framing. Another method is to drape the radiant barrier loosely over the rafters or trusses just before the roof sheathing is applied. When using this method, the barrier should droop so that there is at least 1 inch of air space between it and the underside of the sheathing. The air space makes a radiant barrier more effective.
Some roof sheathing products have a radiant barrier on the surface meant to face the attic. In cases where a flexible radiant barrier is spread over the attic floor installation, look for a permeable product that allows water vapor generated inside the house to pass through the material.
Additional Information
Organization Name | Web Address |
Advanced Energy Corporation (AEC) | |
Affordable Comfort, Inc. | |
Air Conditioning and Refrigeration Institute | |
Air Conditioning Contractors of America (ACCA) | |
Alliance to Save Energy | |
American Architectural Manufacturers Association | |
American Council for an Energy Efficient Economy (ACEEE) | |
American Fiber Manufacturers Association, Inc. (AFMA) | |
American Institute of Architects (AIA) | |
American National Standards Institute (ANSI) | |
American Society for Testing and Materials (ASTM) | |
American Society of Civil Engineers (ASCE) | |
American Society of Heating, Refrigerating and Air-Conditioning Engineers | |
American Society of Interior Designers (ASID) | |
American Society of Mechanical Engineers | |
American Society of Professional Estimators (ASPE) | |
American Subcontractors Association | |
Architecture Engineering Construction Network | |
Associated Builders & Contractors (ABC) | |
Associated General Contractors of America | |
Associated Specialty Contractors, Incorporated | |
Association of Energy Engineers (AEE) | |
Association of Industry Manufacturers Representatives (AIM/R) | |
Blow-In-Blanket Contractors Association (BIBCA) | |
Blue Book of Building & Construction | |
Builders Energy Rater | |
Building Codes Assistance Project (BCAP) | |
Building Envelopes Program (BEP), Oak Ridge National Laboratory | |
Building Green | |
Building Officials and Code Administrators (BOCA) | |
Building Science Corporation | |
Building Trades Directory | |
BuildingOnline | |
California Energy Commission | |
Canadian Office of Energy Efficiency EnerGuide for Houses | |
Cellulose Insulation Manufacturers Association | |
Center for Resourceful Building Technology (CRBT) | |
Central States Insulation Association | |
Construction Specifications Institute (CSI) | |
Energy & Environmental Building Association (EEBA) | |
Energy Design Resources (EDR) | |
Energy Efficient Rehab Advisor | |
Energy Federation Incorporated | |
ENERGY STAR | |
Environsense | |
European Insulation Manufacturers Association (EURIMA) | |
Federal Emergency Management Agency (FEMA) | |
Florida Solar Energy Center (FSEC) | |
Green Builder | |
GreenBuildingSolutions.org | |
Housing Zone | |
Insulation Contractors Association of America (ICAA) | |
Integrated Building And Construction Solutions (IBACOS) | |
Internal Revenue Service (IRS) Energy Efficiency Tax Credit for Homeowners | |
International Code Council (ICC) | |
International Conference of Building Officials (ICBO) | |
International Designers Guild (IDG) | |
Lawrence Berkeley National Laboratory (LBL) | |
Midwest Insulation Contractors Association (MICA) | |
National Association of Energy Services Companies (NAESCO) | |
National Association of Home Builders (NAHB) | |
National Association of Home Builders (NAHB) Research Center | |
National Association of Manufacturers (NAM) | |
National Association of State Energy Officials (NASEO) | |
National Association of the Remodeling Industry | |
National Fire Protection Association (NFPA) | |
National Frame Builders Association (NFBA) | |
National Institute of Building Sciences (NIBS) | |
National Insulation Association (NIA) | |
National Renewable Energy Laboratory (NREL) | |
National Research Council Canada | |
North American Insulation Manufacturers Association | |
Oak Ridge National Laboratory | |
Occupational Safety and Health Administration (OSHA) | |
Oikos | |
Pacific Northwest National Laboratory | |
Partnership for Advanced Technology in Housing (PATH) | |
Polyisocyanurate Insulation Manufacturers Association (PIMA) | |
Residential Energy Services Network (RESNET) | |
Rocky Mountain Institute | |
Safety Glazing Certification Council (SGCC) | |
Southface Energy Institute | |
Southwest Insulation Contractors Association | |
The Association of Energy Engineers | |
The Eastern States Insulation Contractors Association | |
The Metal Building Contractors & Erectors Association (MBCEA) | |
The Southeastern Insulation Contractors Association | |
The Thermal Insulation Association of Canada (TIAC) | |
ToolBase Services | |
U.S. Department of Energy | |
U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy | |
Western Insulation Contractors Association |
