Abstract
The rooftop is a crucial envelope component in terms of impact on building cooling and heating loads. As a result, since 2012, the International Energy Conservation Code (IECC) recommends higher minimum insulation in the roof or attic than any other location. This is true for both residential and commercial buildings, irrespective of climate zone. However, increased insulation in the roof can lead to increased warming of the surrounding ambient environment through convective redirection of heat from the sun to the surrounding airshed. This warming of the urban environment indirectly increases building energy demand for cooling throughout the city. The present study uses building energy simulation to explore and isolate how increases in rooftop solar reflectivity and thermal absorptivity affect building heating and cooling loads, and the resulting convection of heat from roof surfaces into the urban environment. While highly reflective and emissive rooftop surfaces may reduce building cooling loads and urban heating in summer, they may also result in a penalty in terms of winter heating energy demand. As a result, such roofing materials may not be appropriate for regions with considerable heating demand during winter. This study conducts a series of parametric simulations to determine the optimal value for both solar reflectivity and thermal emissivity for different U.S. climate zones. The study incorporates different building models for residential and commercial sectors. The results from this analysis can be used to identify optimal rooftop radiative properties to minimize annual energy costs or to minimize urban warming as a function of building type and climate zone.
Original language | English |
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Title of host publication | ASHRAE Virtual Annual Conference, ASHRAE 2021 |
Publisher | ASHRAE |
Pages | 125-132 |
Number of pages | 8 |
ISBN (Electronic) | 9781955516006 |
State | Published - 2021 |
Externally published | Yes |
Event | 2021 ASHRAE Virtual Annual Conference, ASHRAE 2021 - Virtual, Online Duration: Jun 28 2021 → Jun 30 2021 |
Publication series
Name | ASHRAE Transactions |
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Volume | 127 |
ISSN (Print) | 0001-2505 |
Conference
Conference | 2021 ASHRAE Virtual Annual Conference, ASHRAE 2021 |
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City | Virtual, Online |
Period | 06/28/21 → 06/30/21 |
Funding
The authors gratefully acknowledge the support of this work through a grant by 'The Global KAITEKI Center', a research alliance between Arizona State University and The KAITEKI Institute of Mitsubishi Chemical Holdings Corporation. Also, we would like to thank Ashley Broadbent for helping us to merge the land surface temperature image of Phoenix, AZ (Stuhlmacher and Watkins 2019) with Google Earth Engine.