The joint influence of albedo and insulation on roof performance: A modeling study

Abstract

a b s t r a c tThe advanced Princeton Roof Model (PROM) is evaluated and then applied to quantify the heat transferred through various modular roof structures over an entire year. The goal is to identify an optimal combination of roof reflectivity and insulation thickness that will reduce energy consumption and minimize cost. Meteorological data gathered over the Northeastern United States (Princeton, NJ) is used to force PROM. Our results reveal that for new constructions or for retrofits in the region, an R8.4 (around 46 cm thick roof insulation) white roof (assumed albedo = 0.6 or greater) would significantly reduce the combined heating and cooling load attributable to the roofs. The wintertime penalty of white roofs is also shown to be insignificant compared to their summertime benefits. The findings are pertinent to many other densely populated areas with comparable climates where, despite a much higher number of heating versus cooling degree-days, white roofs are overall advantageous. A cost optimization analysis found that doubling, tripling and quadrupling the insulation thickness from the baseline case of 5.08 cm (2 in.), at an albedo of 0.45, requires 13, 17 and 19 years, respectively, to recover the additional cost incurred.

A Python-enhanced urban land surface model SuPy (SUEWS in Python, v2019.2): development, deployment and demonstration

“…Modifying roof albedo has been suggested extensively as a method to cool urban areas (e.g. Santamouris et al, 2011;Li et al, 2014;Ramamurthy et al, 2015). In the example, we conduct simulations from January 2012 to July 2012 with the first 6 months as the spin-up period.…”

“…to understand energy partitioning over urban surfaces (D. Sun et al, 2017;Wang et al, 2015;Ward and Grimmond, 2017;Zhao et al, 2014), pedestrian level meteorology to diagnose thermal comfort (Bar et al, 2011;Erell et al, 2013;Krayenhoff et al, 2018;Sun et al, 2016;Tan et al, 2009), or ambient radiation and wind conditions to assist building design (Chen, 2004;Jentsch et al, 2013;B. Li et al, 2015;Reinhart and Cerezo Davila, 2016;Santamouris et al, 2001). To obtain such information, accurate and agile modelling capacity of the urban weather and climate are essential.…”

Proposed Measures to Protect Temporary Roofs from Unwanted Heat Gains

“…It is also possible to combine several strategies in this regard. For example, several studies such as Brito and Santos [9], Ramamurthy et al [18], and Arumugam et al [19] found that in hot climates, roofs with combined thermal insulation and reflective coating is the best option. This combination could significantly reduce thermal insulation thickness and thus reduce the cost and maximise energy savings.…”

Cool Roof Impact on Building Energy Need: The Role of Thermal Insulation with Varying Climate Conditions

“…The insulation thickness increase was demonstrated to provide incremental benefits in energy savings which were reduced after a limit. Similarly, Ramamurthy et al [29,30] studied the joint influence of these two roof characteristics on building energy performance through a two-step experimental and numerical analysis. They highlighted the role of both albedo and insulation thickness for the reduction of the annual energy load attributable to the roof, and that wintertime penalties are negligible compared to summertime benefits with cool roofs.…”