Near-Roof Air Temperatures: Modelling the Implications for HVAC Performance and Cool Roofs

Authors

Alan Green, University of WollongongFollow
Laia Ledo Gomis, University of WollongongFollow
Riccardo Paolini
Shamila Haddad
Georgios Kokogiannakis, University of WollongongFollow
Paul Cooper, University of WollongongFollow
Zhenjun Ma, University of WollongongFollow
Buyung Kosasih, University of WollongongFollow
Mattheos Santamouris

RIS ID

143095

Publication Details

Green, A., Ledo Gomis, L., Paolini, R., Haddad, S., Kokogiannakis, G., Cooper, P., Ma, Z., Kosasih, B. & Santamouris, M. (2019). Near-Roof Air Temperatures: Modelling the Implications for HVAC Performance and Cool Roofs. 16th IBPSA International Conference and Exhibition (pp. 1342-1348). United States: International Building Performance Simulation Association.

Abstract

Conventionally in building performance simulations (BPS), it is assumed that air entering outdoor HVAC equipment is at the outdoor ‘ambient’ temperature, obtained from a weather file. However, significant spatial variations exist in outdoor air temperature fields, especially within the thermal boundary layers that form near exposed surfaces like roofs. Experiments were conducted at three large-footprint shopping centre buildings, to characterise the above-roof temperature field. An empirical model was derived from the experimental data, and applied in BPS of a shopping centre with rooftop HVAC equipment in seven Australian climates. In these cases, the electricity savings and gas ‘penalties’ attributable to cool roofs would have been underestimated by 44–85% (61% on average) if near-roof air temperature variations had not been modelled accurately.