Sidebar: Thermal Mass and R-value: Making Sense of a Confusing Issue
Response from Agriboard
I have provided you the Oak Ridge National Laboratory report “Whole Wall Rating/Label for Agriboard Wall Systems.” This report, dated January 30, 1998, on a dynamic ASTM C-236 test and finite difference computer modeling (DOE 2.1E) simulation indicates that the Agriboard 77⁄8” panel has a maximum equivalent performing R-Value of 23.5, given the Southwest region centered in Phoenix. G.Z. Brown observed in his comments on the report that “if one uses the upper limit of the (measured) R-Value from the tests of 17.79 [based on tests from another laboratory—Maxim] and multiplies it by the greatest DBMS (dynamic benefit for massive systems), 1.43 for the Phoenix area, then the effective R-Value would be 25.44 for this combination of conditions.” (Note the DBMS will vary in different climatic conditions.) This maximum result of 23.55 to 25.44 is less than the 28.5 we anticipated but is still a good thermal wall. Panels produced by Agriboard have been subjected to a wide range of ASTM tests required for listing by ICBO. We are continuing with extensive testing this year. Please note that prior to the Oak Ridge tests, our R-values were based on tests of Stramit panels done at Twin City Labs of St. Paul in 1976. These tests on 2” panels produced by a Stramit plant showed k-factors of 0.326 to 0.425 for board between 16-pound and 18-pound density. The test results were provided by Orville Hagenson, a former employee of Stramit Canada. These tests used the ASTM procedure applicable at the time: C-177-45. We have not been able to duplicate the results of those tests. Agriboard R-value extrapolations from these tests were used in absence of any other dependable test data until we could build our own mill and thoroughly test the thermal mass factor of our product. Thermal performance conventionally means R-value, a measure of the thermal resistivity of the component. It is generally understood that R-value is only part of the story, especially for a product like the Agriboard panel, which has tight construction, uniform insulation coverage, and high density and thermal mass. The Oak Ridge tests indicate we have a good thermal product. We are planning extensive additional testing, using rigorously controlled test protocols, and will carefully evaluate the test methodologies. We will share our testing plans and results with you as they are available. We now reference the recent tests done by Maxim and Oak Ridge, and are providing that data as a basis of our estimated R-value. We will be re-running the computer model at Oak Ridge with new empirical data in the coming months and will provide you with the results. Barry Sullivan, President
Agriboard Industries, L.C.
Fairfield, Iowa EDITOR’S RESPONSE: EBN commends Agriboard for investing in such an extensive testing program and, in the process, contributing to our understanding of the mass effect and “effective R-value.” See this issue’s feature article for a detailed look at thermal mass and, particularly, the sidebar on page 13 for specifics on the thermal performance of Agriboard panels in different climates. It is worth noting that even if “effective R-value” is not considered, 77⁄8” (200 mm) Agriboard panels outperform 2x6 walls insulated with fiberglass in almost all situations when whole-wall performance is compared.
