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.
This is the first interim report for project RP1037u1, an extension to the recently completed project RP1037 ‘Driving increased utilisation of cool roofs on large footprint buildings’. Progress so-far in the project and preliminary findings have been summarised in this report.
This report outlines the key outcomes of research project RP1037u1 ‘Above-Roof Temperature Impacts on Heating Penalties of Large Cool Roofs in Australian Climates’, an extension to project RP1037 ‘Driving increased utilisation of cool roofs on large-footprint buildings’. The research has been focused on two key aspects of roof thermal performance that had, up until the time of writing, not been taken into account in most investigations into cool roof technology:
Cool roof technology is known to reduce the cooling energy consumption of conditioned buildings during hot periods, and widespread implementation of such roofs in a neighbourhood or precinct can mitigate the urban heat island effect.
The implementation of ‘cool’ roofing materials, with high solar reflectance and infrared emittance, has received significant attention in recent years, as a method to mitigate the urban heat island effect and reduce building cooling energy requirements. The effect of ‘cool’ roofs on heat transfer through the roof structure has been investigated by many researchers. However, the air temperature field above roofs and the influence of elevated above-roof air temperatures on the performance of rooftop air-conditioning equipment and photovoltaic panels have not been studied in depth.