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May 4, 1998
For Immediate Release
For more information, contact Jennifer Grover or Bruce McIntosh at PCA (847) 966-6200.
PCA Joins President Clinton’s Innovative Housing Initiative
At a housing development near Los Angeles today, President Clinton announced a new private/public partnership to make American homes safer, stronger, and more energy efficient.
Called the Partnership for Advancing Technology in Housing, or PATH, the program brings together federal agencies, local officials, and product manufacturers to accelerate the acceptance of new technologies.
The Portland Cement Association, a trade association based in Skokie, Ill., supports the Administration’s efforts and has joined PATH with new concrete building systems for housing.
PCA has fostered development of several new concrete home-building technologies. A system called insulating concrete forms or ICFs, in which concrete is placed between two layers of polystyrene, builds homes that meet and exceed PATH’s objectives.
A key goal of PATH is energy efficiency. Because ICF walls consist of a concrete core surrounded by foam insulation, homes built with them require far less energy. Research conducted by Dr. Pieter VanderWerf at Boston University shows that home built with ICF walls require 44% less energy to heat and 32% less energy to cool than standard wood-frame homes.
In addition to savings for the homeowner, such high energy efficiency could represent a significant reduction in greenhouse gas emissions and global warming.
ICF homes are also stronger and more durable than their conventional wood frame counterparts. Recent tests at Texas Tech University’s Wind Engineering show that concrete walls can withstand flying debris carried by winds of more than 200 mph. Such conditions cover 99% of all tornadoes and virtually all hurricane-force winds.
As a trade association of U.S. and Canadian cement companies, PCA conducts research, market development, and educational programs on concrete and its key ingredient, cement.
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Wall System Background
Concrete’s Invisible Innovation in Wall Systems
Insulating concrete form assemblies are an innovative building system hidden from view under sheetrock and siding. Underneath the standard covering lies polystyrene insulation and solid built-to-last concrete walls.
European builders have used the foam forming systems successfully for decades, but they recently have made a mark in North America. The builder-friendly wall system—featured on the TV series “This Old House” and “HomeTime,” as well as in Better Homes and Gardens, Southern Living, and many NAHB show homes—has found its way into many new homes across every region and in every price range. Homes built with concrete walls can look at home anywhere, because the system accommodates any architectural style.
ICFs are a variation of traditional cast-in-place walls. In conventional cast-in-place construction, a crew erects forms of plywood, steel, or aluminum that make a mold in the shape of the desired walls. After placing rebar to reinforce the wall, the crew pours concrete inside the cavity. Once the concrete hardens, the crew strips the forms to leave the reinforced concrete walls. With ICFs, the forms are left in place after the concrete hardens. The polystyrene functions as the insulation and the concrete functions as the structure.
ICFs are produced with expanded or extruded polystyrene containing up to 20 percent recycled materials. Expanded polystyrene is formed by expanding plastic beads in a mold and is similar to vending machine coffee cups. Extruded polystyrene is made by expanding plastic resin and extruding through a die and is similar to grocery store meat trays. Foam form units provide 2 inches (5 cm) of insulation on both faces of a concrete wall, which is usually 4 to 6 inches (15 cm) thick. The result is a solid 8- to 10-inch (25-cm) thick assembly with strong thermal properties that holds down energy costs. The integral, permanent insulation allows builders to create super-insulated walls in a fraction of the time required with wood or steel frame.
Two types of ICF systems are available. One uses hollow, polystyrene blocks that stack and interlock almost like children’s building blocks, and the other uses panels or planks that are held a constant distance apart by a series of plastic ties.
After using polystyrene forms to construct a hollow wall with vertical and horizontal reinforcement, contractors pump concrete into the cavity to create a solid structural wall with insulation on both sides. Once crews complete the wall, electricians cut channels for cables and wires into the forms. Plumbers work in a similar way, placing cold and hot water lines in the insulation after the concrete is poured.
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Benefits Of Concrete Homes
Energy Efficiency:
Houses built with ICF exterior walls require an estimated 44% less energy to heat and 32% less energy to cool than comparable wood frame houses.
Source: Vanderwerf, “Energy Consumption Comparisons of Concrete Homes versus Wood Frame Homes,” Portland Cement Association, 1997.
Acoustical Performance:
About one-third as much sound gets through an ICF wall compared with an ordinary frame wall.
Source: Vanderwerf, Feige, Chammas, and Lemay, “Insulating Concrete Forms for Residential Design and Construction,” McGraw Hill, 1997.
Fire Safety:
ICF walls will withstand up to four hours of intense fire and temperatures without structural failure, compared with wood frame that will fail in one hour or less.
Sources: Underwriters Laboratories Inc., “Fire Resistance Directory,” 1988. Concrete and Masonry Industry Firesafety Committee, “Analytical Methods of Determining Fire Endurance of Concrete and Masonry Members- Model Code Approved Procedures,” 1994.
Fire is five times more likely to spread when exposed to wood compared to exposure to plastic foams used in ICFs.
Source: Vanderwerf, Feige, Chammas, and Lemay, “Insulating Concrete Forms for Residential Design and Construction,” McGraw Hill, 1997.
When exposed to fire, the emissions from plastic foams are no more toxic than those released by wood.
Source: Grand, Kaplan, and Harzell, “A Literature Review of the Combustion Toxicity of Expanded Polystyrene,“ Final Report, SwRI Project No. 01-8818-507, Southwest Research Institute, San Antonio, May 1986.
Tornado/Hurricane Resistance:
Debris driven by 250-mph tornado-force winds will penetrate through typical wood frame construction but will be stopped and fail to damage the concrete within ICF construction.
Source: Kiesling and Carter, “Investigation of Wind Projectile Resistance of Insulating Concrete Form Homes,” Texas Tech University Research Report, 1998.
Indoor Air Quality:
Volatile organic compound emissions from concrete building products are lower than those observed for most other building materials and do not present a health risk.
Source: Budac, “Concrete’s Role in the Indoor Air Environment,” Portland Cement Association, 1998.
Structural Strength:
Calculations show that a 4-inch concrete wall built using 3000 psi concrete and #4 bars at 32 inches has over twice the bending capacity of a wood frame wall built using 2 x 4 studs at 16 inches.
Source: Unpublished calculations.
For additional information call PCA’s toll-free Concrete Homes Hotline at 888/333-4840 or visit the concrete homes web site at www.concretehomes.com.
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