Low-slope roofing assemblies include a wide range of insulation and single ply membrane attachment methods. Previous studies have shown that mechanical attachment using metal fasteners leads to significant thermal bridging and consequent loss of insulation value and reduction of long term thermal efficiency. This study calculates the costs associated with mechanical attachment in terms of lost insulation value, increased long-term energy costs, and the material and labor costs associated with installation of these common systems. Energy efficiency reductions using metal fasteners were modeled for eight US cities in a range of climate zones. From the data, it was possible to calculate target costs (labor plus materials) that would make adhered systems cost effective. There are many options available to adhere single ply roof system components, such as solvent-based adhesives and low-rise urethane foams, together with different application approaches such as broom, spray, and ribbon methods. The cost targets derived in this study can help optimize the use of such materials and application methods such that the thermal bridging due to fasteners could be substantially reduced or eliminated.
References
[1]
US Energy Information Administration. https://www.eia.gov/energyexplained/use-of-energy/commercial-buildings.php
[2]
IEA (2013) Transition to Sustainable Buildings: Strategies and Opportunities to 2050. OECD, IEA, Paris, France.
[3]
Building Envelope Thermal Bridging Guide (2016) BC Hydro Power Smart, Version 1.1. https://www.bchydro.com/content/dam/BCHydro/customer-portal/documents/power-smart/buil ders-developers/building-envelope-thermal-bridging-guide-1.1.pdf
[4]
Taylor, T.J. (2019) Reflective Roofing Use on Commercial Buildings in the United States: An Energy Type and Cost Analysis. Buildings, 9, 212. https://doi.org/10.3390/buildings9100212
Taylor, T.J., Willits, J., Hartwig, C.A. and Kirby, J.R. (2018) Insulation Value Optimization for Low-Slope Roofs. Building Envelope Technology Symposium.
[7]
Burch, D.M., Shoback, P.J. and Cavanaugh, K. (1987) A Heat Transfer Analysis of Metal Fasteners in Low-Slope Roofs. In: Roofing Research and Standards Development, ASTM International, West Conshohocken, PA, 10-22. https://doi.org/10.1520/STP25721S
[8]
Olson, E.K., Saldanha, C.M. and Hsu, J.W. (2015) Thermal Performance Evaluation of Roofing Details to Improve Thermal Efficiency and Condensation Resistance. In: Molleti, S. and Rossiter, W.J., Eds., Roofing Research and Standards Development, Volume 8, ASTM International, West Conshohocken, PA, 10-22. https://doi.org/10.1520/STP159020150021
[9]
Singh, M., Gulati, R., Srinivasan, R.S. and Bhandari, M. (2016) Three-Dimensional Heat Transfer Analysis of Metal Fasteners in Roofing Assemblies. Buildings, 6, 49. https://doi.org/10.3390/buildings6040049
Cusick, M., Wang, L. and Griffin, C. (2014) New LTTR Values and What They Mean for Roofing Industry Professionals. Roofing Contractor, Troy, MI.
[19]
Pallin, P., Kehrer, M. and Desjarlais, A. (2014) The Energy Penalty Associated With the Use of Mechanically Attached Roofing Systems. Proceedings of the Symposium on Building Envelope Technology, Tampa, FL, 20-21 October 2014.
[20]
Molleti, S., Baskaran, B., Kalinger, P., Graham, M., Cote, J.F., Malpezzi, J. and Schwetz, J. (2015) Evaluation of Air Leakage Properties of Seam-Fastened Mechanically Attached Single-Ply and Polymer-Modified Bitumen Roof Membrane Assemblies. In: Molleti, S. and Rossiter, W.J., Eds., Roofing Research and Standards Development, Volume 8, ASTM International, West Conshohocken, PA, 30-43. https://doi.org/10.1520/STP159020150025