s the Cold War really over? Well, yes and no.
Centuries before Nikita Khruschev's pounding shoe became a tool of international diplomacy and a symbol of the icy staredown between the United States and the Soviet Union, another kind of cold war was being waged--every winter, by people trying to build shelters that would keep the cold out and the heat in.
At ORNL's Building Envelope Research Center (BERC), modern-day cold warriors carry on the struggle using high-tech analytical tools. Formerly known as the Roof Research Center, BERC is the result of a cooperative effort between government agencies and private industry to develop more efficient and environmentally friendly techniques for constructing both residential and commercial buildings.
The center's new, vise-like Rotatable Climate Simulator clearly illustrates the center's research mission. Stenciled letters identify one side as HOT and the other as COLD. In between is a removable wall section, studded with temperature sensors. Determining how well walls and other building components keep the HOT side hot and the COLD side cold is the primary focus of research at the center.
As the center's name implies, BERC scientists study building envelopes--foundations, walls, windows, and roofs. "Our job," says BERC director Jeff Christian, "is to work with private industry to make building components more energy efficient. Our vision is to be the world's foremost center of excellence in the development of globally competitive building envelope technologies--already, a third of our staff is made up of visiting researchers, from both the United States and abroad."
BERC's research efforts are concentrated around four specially designed test facilities.
Large-Scale Climate Simulator (LSCS). The performance of a roof system depends on a number of factors, including temperature, humidity, and exposure to the sun. Rather than sitting on a roof until the right weather came along, BERC researchers developed the LSCS. This test facility allows roof systems up to 4 meters (13 feet) square to be exposed to any combination of temperature, moisture, or sun conditions on earth.
Using the LSCS, ORNL researchers working with Energy Saving Solutions, Inc., a private insulation manufacturer, determined that, under cold winter conditions, up to 50% of the heat loss through attics insulated with some types of low-density, loose-fill fiberglass is a result of convection--warm air circulating through the insulation.
Researchers confirmed the presence of this convection cycle by analyzing infrared photographs of the top surface of various types of attic insulation. Infrared photos of low-density, loose-fill fiberglass attic insulation showed a pattern of six-sided hot and cold areas that is characteristic of convection heat loss. This evidence, combined with direct measurements of ceiling heat loss in the LSCS, led researchers to question the effectiveness of some common types of blown-in fiberglass insulation in very cold weather.
To help solve this problem, BERC worked with Energy Saving Solutions to evaluate the effectiveness of different insulation covering systems designed to reduce convection-related heat losses. Building on this research, Energy Saving Solutions developed a way of wrapping fiberglass batts in plastic bags that can be laid on top of existing insulation. The bags are designed to "breathe," allowing moisture to pass through the insulation while eliminating nearly all heat losses caused by convection.
Researchers estimate that, if changes can be made in overhead insulation to completely eliminate convection, overall heat loss through residential ceilings in cold climates could be reduced by as much as 20%. These findings have already had an effect on state building codes. Recently, Minnesota authorities beefed up their code to require that manufacturer claims of insulation performance hold up even in the coldest expected weather. This collaborative effort earned BERC a 1992 "Best of What's New" award from Popular Science for significant achievement in science and technology, one of only ten in the building products category.
The unique capabilities of the LSCS have also enabled researchers to determine that small amounts of moisture trapped in the insulation of flat, commercial-type roofs like those found on many schools, factories, and shopping malls, can seriously damage their performance. "Trapped moisture is a big problem with flat roofs," says Christian. "That's why we are developing a guidebook to help building owners decide whether to replace or re-cover their roofs." The decision to replace old roofs can be further complicated by growing restrictions on disposal of used roofing materials, particularly those containing asbestos.
Currently, the facility is being used to test the moisture absorbency and drying rates of five different commercially available roof sections, with the goal of developing faster-drying, more durable roofing material. "The key to solving this problem," Christian says, "is to provide a way for water vapor to exit the roof."
To help improve the performance of flat roofs, ORNL and Dow Corning, Inc., are collaborating to demonstrate reroofing techniques that trap little or no moisture. Experimental roofing systems will be installed on the ORNL cafeteria and on Building 2518 later this year. Heat transfer data will be collected before and after the roofs are installed to measure their effect on the energy efficiency of the buildings.
Roof Thermal Research Apparatus (RTRA). For lower-cost field testing of flat roofing sections, BERC researchers rely on the RTRA. This climate-controlled facility actually serves three purposes. Its removable roofing sections allow roof system samples as small as 1.2 meters (4 feet) square to be tested, and the facility's walls are equipped with four test frames for studying the thermal performance of exterior, aboveground masonry walls. Two test areas for study of slab-on-grade, or ground-level, foundation insulation are also available.
Data on up to 14 test systems can be collected simultaneously at the facility and can be integrated with data from the complete weather station at the site.
The RTRA roof is now being used to determine the long-term performance of coatings designed to save energy by keeping the surface of the roof cooler than a typical black roof by reflecting sunlight rather than absorbing it.
Envelope Systems Research Apparatus (ESRA). The construction and operation of the ESRA is a result of unprecedented cooperative research and development agreements (CRADAs) among DOE, the Environmental Protection Agency, and several private companies. The information gathered from this joint effort has been so rewarding for its industrial partners that they recently extended their participation in the project for three more years and doubled their financial support of the facility.
Like the RTRA, the larger ESRA can be used for both roof and foundation studies. Up to 40 different roof sections can be tested at once on this facility. Its current roof is made up of several common roofing systems that are insulated with experimental polyisocyanurate foam. This common type of insulation is usually manufactured using chlorofluorocarbons (CFCs), chemicals that also break down the protective layer of ozone in the earth's stratosphere, but the experimental materials are CFC-free. Research being conducted at ESRA on this new insulation will thoroughly document its performance, contributing to the successful marketing of this more environmentally acceptable product.
Because the facility's foundation is covered with "designer dirt," soil with uniform and known properties, it is ideal for conducting studies of heat and humidity transfer from residential or small commercial foundations to the surrounding soil. Results of this research are being used to validate the computer models used to develop the national building code standards for foundation insulation. Several builder handbooks have also been developed from these models.
Rotatable Climate Simulator (RCS). Donated to ORNL by Dow Chemical Corporation, the RCS is the newest addition to BERC's cold-war arsenal and has been upgraded by BERC researchers to provide state-of-the-art analyses of walls, floors, doors, and windows. "Getting the RCS operational required assembling a large in-house team from four ORNL divisions, including Instrumentation and Controls, Plant and Equipment, Engineering, and Energy," says Christian. "This experience was good for building the cooperation and internal teamwork that will be needed to maintain and extend this facility's capacity."
The RCS can accommodate wall, floor, or roof sections up to 4 meters by 3 meters (13 feet by 10 feet), including masonry walls, and it can simulate almost any combination of temperature, air pressure, and wind. It also meets or exceeds American Society for Testing and Materials requirements for this kind of test facility.
Christian predicts that, within the next few years, manufacturers will be required to include thermal performance rating labels on windows, doors, skylights, and, eventually, prefabricated wall sections. "As more and more engineered building components come on the market," he adds, "we have to position ourselves to be a major player in the area of factory-produced housing."
The center is already playing a major role in many areas. For example, BERC has been active in development of the American Society of Heating and Refrigeration Engineers' standard for energy-efficient design of new low-rise residential buildings. When completed, this standard will replace an earlier version that has been adopted in 45 of the 50 states.
Most recently, BERC researchers and their counterparts in the Energy Division have launched a new cold-war offensive by establishing the Building Technology Center. Expected to begin operations later this year, the center will be made up of BERC and several Energy Division groups that are developing and implementing state-of-the-art heating and cooling technologies for new and existing buildings.--Jim Pearce