Temperature-Dependent Thermal Performance of Closed-Cell Foam Insulation Board in Roof Constructions
Publication: Journal of Cold Regions Engineering
Volume 34, Issue 3
Abstract
Thermal performance of an insulation material is influenced by the in-service temperature condition. Unlike most other insulation materials, thermal resistance (R-value) of polyisocyanurate (polyiso or PIR) foam insulation with “captive blowing agent” varies nonlinearly with temperature. Building designers consider the constant R-value of different insulating materials for building design and energy calculations, and hygrothermal simulation software tools, such as WUFI, consider the linear temperature-dependent R-value, even for polyiso. However, neither the linear temperature-dependent thermal resistance nor the constant thermal resistance value of polyiso represents the actual thermal performance. This paper aims to quantify the impact of in-service boundary temperature conditions in Canadian climates on the thermal performance of polyiso foam insulation board used in EPDM and PVC roof constructions. Hygrothermal simulations were performed using WUFI Pro, which considers real climate data and hygrothermal properties of constituent roof components for evaluating moisture and temperature conditions in roof constructions. Based on heating degree days (HDD), ten different cities were selected between climate Zone 4 (HDD < 3,000) and Zone 8 (HDD ≥ 7,000). The thermal resistance measurements were conducted using heat flow meter apparatus on four polyiso insulation boards (two new and two aged) of different sizes [thickness, new: 1 in. (25 mm) and 2 in. (51 mm); aged: 2 in. (51 mm) and 3 in. (76 mm)] at five mean temperatures of −4°C (25°F), 4.5°C (40°F), 10°C (50°F), 24°C (75°F), 43°C (110°F), and at a temperature differential of 28°C (50°F). The measured thermal resistance data of the four samples at different mean temperatures were normalized with calculated thermal resistance of each sample at 22°C (72°F). The normalized R-value variation was calculated using in-service boundary temperature conditions determined from hygrothermal simulations and considering linearly varied thermal resistance with temperature, for the selected ten Canadian cities. The normalized R-value data of four polyiso samples revealed 17.4% decrease in R-value under winter conditions of Zone 8.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The authors would like to acknowledge financial support from Natural Sciences and Engineering Research Council (NSERC) of Canada. The authors would also like to thank Peter Klinger and Wendy Fraser from Canadian Roofing Contractors Association (CRCA) who were involved in this research project and provided valuable technical assistance at regular intervals throughout the research project. Matthew Walker and Armin Aini are also acknowledged for assistance with sample preparation and laboratory activities throughout the project.
References
ASHRAE (American Society of Heating, Refrigeration and Air-Conditioning Engineers). 2017. ASHRAE handbook-fundamentals. Atlanta, GA: ASHRAE.
ASTM. 2013. Standard practice for calculating thermal transmission properties under steady-state conditions. ASTM C1045-07. West Conshohocken, PA: ASTM.
ASTM. 2015. Standard practice for selecting temperatures for evaluating and reporting thermal properties of thermal insulation. ASTM C1058/C1058M-10. West Conshohocken, PA: ASTM.
ASTM. 2017. Standard test method for steady-state thermal transmission properties by means of the heat flow meter apparatus. ASTM C518-17. West Conshohocken, PA: ASTM.
Bailes, A. A. 2014. “Building science.” Accessed January 14, 2017. http://www.greenbuildingadvisor.com; http://www.greenbuildingadvisor.com/blogs/dept/building-science/calculating-heating-degree-days.
BC (Building Codes). 2012. “Part 9-housing and small buildings.” Accessed January 10, 2018. http://free.bcpublications.ca/civix/document/id/public/bcbc2012/ep001029.37.
Berardi, U., and M. Naldi. 2017. “The impact of the temperature dependent thermal conductivity of insulating materials on the effective building envelope performance.” Energy Build. 144: 262–275. https://doi.org/10.1016/j.enbuild.2017.03.052.
BSC (Building Science Corporation). 2013. Understanding the temperature dependence of R-values for polyisocyanurate roof insulation. Westford, MA: BSC.
Budaiwi, I., A. Abdou, and M. Al-Homoud. 2002. “Variations of thermal conductivity of insulation materials under different operating temperatures: Impact on envelope-induced cooling load.” J. Archit. Eng. 8 (4): 125–132. https://doi.org/10.1061/(ASCE)1076-0431(2002)8:4(125).
CGSB (Canadian General Standards Board). 1992. Thermal insulation, block or blanket, elevated temperature. CAN/CGSB-51.5-92. Ottawa, ON, Canada: CGSB.
CRCA (Canadian Roofing Contractors Association). 2011. Roofing specifications manual. Ottawa, ON, Canada: CRCA.
Drouinp, M., and P. Kalinger. 2001. “Closed cell foam insulations: Resolving the issue of thermal performance.” Construction Canada Magazine, January 27, 2018.
DuPont. 2011. “Temperature effect on insulation value of polyurethane foams, Technical Information ABA-14.” Accessed December 15, 2017. https://www.chemours.com/Formacel/en_US/assets/downloads/h54876_temperature_effect_on_R_value.pdf.
EnergyPlus. 2017. Weather data. Golden, CO: NREL.
Fraunhofer IBP (Fraunhofer Institute for Building Physics). 2017. “Home.” Fraunhofer Institute for Building Physics. Accessed January 5, 2018. https://wufi.de/en/.
Graham, M. 2010. “R-value concerns” Professional Roofing. Accessed January 13, 2018. http://www.professionalroofing.net/Articles/Tech-Today--05-01-2010/1686.
Graham, M. 2015. “Testing R—values” Professional Roofing. Accessed January 13, 2018. http://www.professionalroofing.net/Articles/Tech-Today--03-01-2015/3608.
Holladay, M. 2015. “Cold weather performance of polyisocyanurate insulation.” Green Building Advisor. Accessed 22 March 2018. https://www.greenbuildingadvisor.com/article/cold-weather-performance-of-polyisocyanurate.
Mukhopadhyaya, P., M. T. Bomberg, M. K. Kumaran, M. Drouin, J. C. Lackey, D. Van Reenen, and N. Normandin. 2004. “Long-term thermal resistance of polyisocyanurate foam insulation with gas barrier.” In Proc., 9th Int. Conf. on Performance of Exterior Envelopes of Whole Buildings, 1–10. Oak Ridge: Oak Ridge National Laboratory.
NRC (National Research Council). 2015. National building code of Canada, 2015. Ottawa, Canada: National Research Council Canada.
NRCAN (Natural Resources Canada). 2012–2015. Secondary energy Use and GHG emissions by End Use—Including electricity-related emissions. Ottawa, Canada: Natural Resources Canada.
NRCAN (Natural Resources Canada). 2014. Energy and greenhouse Gas emissions (GHGs). Ottawa, Canada: Natural Resources Canada.
Pelanne, C. M. 1978. “Thermal insulation: What it is and how it works.” J. Therm. Insul. 1 (4): 223–236. https://doi.org/10.1177/109719637800100401.
PIMA (Polyisocyanurate Insulation Manufacturing Association). 2018. “FAQ.” Accessed October 4, 2017. https://www.polyiso.org/page/FAQ.
TenWolde, A. 2008. “ASHRAE standard 160P-criteria for moisture control design analysis in buildings.” ASHRAE Trans. 114 (pt. 1): 167–171.
Information & Authors
Information
Published In
Journal of Cold Regions Engineering
Volume 34 • Issue 3 • September 2020
Copyright
© 2020 American Society of Civil Engineers.
History
Received: May 1, 2019
Accepted: Dec 23, 2019
Published online: May 21, 2020
Published in print: Sep 1, 2020
Discussion open until: Oct 21, 2020
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.