Economic Impact of Improved Service-Life Prediction for Seams in Low-Slope EPDM Roofing
Douglas S. Thomas
In the early part of the 1970's built-up-roofing dominated the U.S. membrane roofing industry. It was estimated that 10 to 15 percent of these roofs failed, but by the late 1980's new membranes were being rapidly adopted. Among them, EPDM (ethylene-propylene-diene terpolymer) rubber, manufactured as preformed single-ply sheets ready for field installation, experienced the most rapid growth; however, problems arose with this product due to disbonded seams located at buckles and ripples in the membrane. National Institute of Standards and Technology (NIST) researchers designed and constructed an analytical laboratory exposure device in which the primary environmental weathering factors (e.g., temperature, moisture, and spectral ultraviolet irradiance) could be independently, precisely, and accurately monitored and controlled over long exposure periods. This research resulted in vast improvements in the performance of EPDM roofing. This paper examines the economic impacts of the research conducted by NISTs Service Life Prediction (SLP) Program for EPDM roofing. Three ASTM standards are used to calculate the value of NISTs research investment: (1) present value of net savings (PVNS (E1074)), (2) savings-to-investment ratio (SIR (E964)), and (3) adjusted internal rate of return (AIRR (E1057)). The results show that the PVNS attributable to NIST is $26.7 million with an SIR of 2.5 and AIRR of 13.7 %. Stated in present value terms, every public dollar invested in NISTs SLP-related research, development, and deployment effort generated $2.5 in cost savings to the public.