Effect of radiative cooling on heat transfer through building partitions

Abstract

The article analyses the impact of radiative cooling on heat loss in buildings. Radiative cooling means a temperature decrease of external surfaces of building partitions below the ambient temperature. The phenomenon occurs in certain conditions – cloudless sky at night, on horizontal and inclined building surfaces. Based on the dependencies recommended in literature and standards, a mathematical model describing heat transfer in the conditions of radiative cooling has been adopted. The analysis was based on two models of building partitions, i.e. roof-ceiling and insulating glass unit (IGU). For a roof-ceiling, the study analyses the impact on heat loss in the conditions of radiative cooling of such factors as thermal insulation thickness, wind speed, surface emissivity, etc. Heat losses occurring in the conditions of a cloudless and overcast sky have been compared. For IGUs, the study analyses the impact of radiative cooling on heat transfer by convection and radiation in the sealed gas-filled gap. The results of own experimental testing of temperature drop on the surface of IGUs in operating conditions are also presented. It was found that radiative cooling of building partitions in certain weather conditions has a significant effect on heat losses, which should be included in calculations, particularly in the case of horizontal and inclined partitions.