Evaluation of passive envelope systems with radiative sky cooling and thermally insulated glazing materials for cooling

Abstract

Passive envelope systems for building cooling are of great significance to achieve sustainable and low-energy buildings. Although promising advances in radiative sky cooling and enhanced glazing materials have been achieved recently, there still lacks performance evaluation on integrating these novel materials as passive building envelope systems for the cooling purpose. To this end, the study newly proposes a passive envelope system by synthetically incorporating radiative cooling roofs, colored cooling walls and thermally insulated glazing windows into a standard-compliant commercial building archetype. Comprehensive building thermal, energy, economic and environmental performance across a variety of typical climates in the United States was evaluated. The results were compared to the baseline model, in which the envelope properties are location-dependent and in accordance with ASHRAE Standard 90.1 (β = 0.3, βvis = 0.3, ε = 0.9 for exterior walls, β = 0.23–0.55, ε = 0.75–0.9 for roofs, and U = 1.9–2.8, SHGC = 0.23–0.38, VT = 0.253–0.418 for windows). The highly solar reflective and thermally emissive radiative cooling coating (β = 0.98, ε = 0.97) applied on roofs is able to achieve the cooling electricity savings ranging from 8.2% to 29.7% in response to different climate regions. In comparison, the colored (yellow) cooling paint (β = 0.72, βvis = 0.59, ε = 0.95) applied on walls can achieve annual cooling energy savings regionally from 3.5% to 9.3%. Besides, the thermally insulated windows with the improved visual comfort can save cooling energy from −2.1% to 3.7%. From the maximized cost saving perspective, the optimal design schemes of passive cooling building envelopes for each region were accordingly determined, by which the net cost saving ranges from 0.03 to 2.13 $/(m2·year) in response to climate variability. Notably, the optimal building envelopes regionally correspond to the net avoided CO2 emissions ranging from 0.11 to 16.72 kg/(m2·year)), indicating the noticeable carbon neutral potential induced by the proposed passive envelope system. This research is an effort to provide effective passive cooling envelope systems by combining the existing advanced cooling materials towards sustainable and energy-efficient buildings.