Thermal performance of retrofitted secondary glazed windows in residential buildings: two cases from Australia

Purpose: This study presents the results of empirical measurements of the thermal performance of retrofitted secondary glazed windows, involving installation of an additional windowpane, in a residential context in Australia. Design/methodology/approach: In situ temperature measurements were collected from the surfaces of retrofitted secondary glazed windows in two residential buildings in the Australian Capital Territory. The heat loss savings and subsequently the electricity savings were calculated based on these temperature measurements. Findings: Heat loss reductions of up to 60.8% and electricity savings of up to 9.96% could be achieved by retrofitting single glazed windows with secondary glazing. The findings suggest that the thermal performance of retrofitted secondary glazed windows is comparable to double glazed windows. Practical implications: Multiple glazed windows provide better energy efficiency, thermal and acoustic performance compared to single glazed windows. It is estimated, however, that 85% Australian buildings still have single glazed windows. Secondary glazing has emerged as a cost-efficient and easier-to-install alternative to double glazed windows. The results of this research can contribute to a wider market uptake of secondary glazed windows in Australia by showing that they have similar thermal performance to double glazed windows. Originality/value: This research is a first attempt to empirically measure the thermal performance of retrofitted secondary glazed windows with an additional windowpane in a residential setting in Australia. Secondary glazing is the provision of an additional windowpane to the original single glazed window. Previous studies in Australia have focused on performance of double glazed windows.