STYROFOAM T-MASS Technology
Thermal Mass Effect
Insulated concrete sandwich walls constructed with STYROFOAM™ T-MASS™ Technology effectively utilize the thermal mass effect of concrete to create an “equivalent wall performance R-value” several times greater than what is estimated by a traditional material R-value calculation.
How it works
Resistance to the flow of heat is measured in “R-value’ – the higher the R-value, the harder it is for heat to get through. STYROFOAM extruded polystyrene insulation is rated at an R-value of 5.0 per inch at 75°F. The material R-value for the entire wall assembly is derived by adding an R-value of 0.08 per inch for concrete along with an interior air film coefficient that produces an R-value of 0.68 and an exterior air film coefficient that produces an R-value of 0.17. A wall utilizing STYROFOAM T-MASS Technology with a 2-inch exterior layer and a 4-inch interior layer of concrete along with a 2-inch layer of STYROFOAM extruded polystyrene insulation would result in a material R-value of approximately 11.33.
All materials have intrinsic mass based on their specific heat capacity. By designing a wall to have a significant layer of concrete adjacent to the interior space and a thinner concrete layer exposed to the climate, the wall behaves with a dynamic performance that is several times greater than what can be estimated by the material R-value. This feature is referred to as the mass performance R-value or the equivalent wall performance R-value due to the utilization of concrete’s thermal mass.
The degree of improvement in R-value in a given structure is greatly dependent upon the climate location, the occupancy type and the orientation as well as the building design. Typically, residences constructed with STYROFOAM T-MASS Technology in the Midwest U.S. will see an equivalent R-value roughly twice that of the material R-value. In the Southern U.S. the equivalent R-value can be as much as three times or greater than the material R-value.
By placing a highly effective layer of STYROFOAM extruded polystyrene insulation between the two concrete layers, the interior temperature will warm the interior layer of concrete. Once this interior layer hits its maximum capacity to store this energy it will release it, transferring it back into the interior of the building (not unlike how a battery works). Therefore the effect on the HVAC system is a substantial as there is a shifting of heating and cooling loads to off-peak hours when electricity is less expensive. The economic impact is the same or better than increasing the insulation. The performance can actually be better than additional insulation in that mass of the concrete allows for a natural energy load shift that insulation cannot provide.
STYROFOAM* T-MASS Technology has effectively assembled the building components necessary to create a cost-effective, energy-efficient, multi dimensional housing system. Research into the exact impact of the thermal mass effect on STYROFOAM* T-MASS Technology is described in detail below.
Third Party Testing
Oak Ridge National Laboratory (ORNL) has performed a significant amount of research into the dynamic thermal performance of this wall technology, most notably in the report, “Whole Wall Rating/Label for Thermomass®1 Wall Systems with Prefabricated Concrete Sandwich Panels” by Jan Kosny, Andre Desjarlais, Phill Childs, and Jeff Christian. This report defines the methods of analysis and computer modeling used to analyze the steady state thermal performance and dynamic thermal performance of the wall system. These models effectively simulated single-family residences in six representative U.S. climates, comparing T-MASS wall units to identical buildings simulated with lightweight 2x4 wood frame exterior walls.
The results of this study were tabulated to show comparative R-values which would be needed in conventional wood frame construction to produce the same loads as insulated sandwich walls utilizing STYROFOAM T-MASS Technology. The six climates tested were Atlanta, Denver, Miami, Minneapolis, Phoenix, and Washington, D.C. Of these cities, the difference was most dramatic in Phoenix, where a comparable R-value of conventional wood frame exterior wall would need to be 2.9 times higher than the steady state R-value of an insulated T-MASS wall to produce the same loads. Therefore a comparative wood frame wall R-value should be R-31 to achieve the same effect as an insulated sandwich wall utilizing STYROFOAM T-MASS Technology. This data is directly linked to ASHRAE 90.1 90.2 and the Model Energy Code and is the preferred choice of simulating dynamic mass structures.
About Dow Building Materials
A business unit of The Dow Chemical Company, Dow Building Materials manufactures STYROFOAM* insulation products, which have been used for more than 50 years by builders, architects and consumers worldwide. With global sales in 13 different market segments, STYROFOAM insulation commands a large share of the worldwide insulation market. STYROFOAM, one of the world's most recognized brands, now includes extruded polystyrene insulation, polyisocyanurate insulation, housewrap and extruded polypropylene insulation. STYROFOAM insulation has been used to insulate millions of homes and buildings. Dow has been a proud and active supporter of Habitat for Humanity International since the early 1980's and was the first corporate sponsor. For further information, visit www.insulateyourhome.com.
Dow is a leading science and technology company that provides innovative chemical, plastic and agricultural products and services to many essential consumer markets. With annual sales of $28 billion, Dow serves customers in more than 170 countries and a wide range of markets that are vital to human progress, including food, transportation, health and medicine, personal and home care, and building and construction, among others. Committed to the principles of Sustainable Development, Dow and its approximately 50,000 employees seek to balance economic, environmental and social responsibilities.
For Editorial Information:
Jan McKinnon
The Dow Chemical Company
519-339-5028
Bob Plishka
The Dow Chemical Company
989-636-0462
41-44-728-2371
