Energy saving potential of low-e coating based retrofit double glazing for tropical climate

•Real life test bedding of low-e coating based retrofit double glazing in tropical climate, was conducted.•Retrofit double glazing can lead up to 4% annual energy savings when installed on a clear glass for tropical climate and up to 7.5% for retrofit double glazing installed in grey tinted glass (under Singapore climatic conditions).•Lux levels were reduced by 75% after installation of retrofit double glazing.•Mean radiant temperatures at the centre of the room was 1.3 °C lower after installation of retrofit double glazing. Double glazed facades are a well established feature for buildings located in cold ambient climate. In tropical climate there has been some penetration of Double Glazing Units (DGU) to reduce air-conditioning load. However, for existing buildings with older glass (usually having lower thermal insulation and higher solar transmission) a simple retrofit solution is to attach a low-e (hard coat) coated glass internally in the building without an explicit air tight seal. To analyse the proposed retrofit double glazing solution, experiments were conducted in a fully instrumented living lab to observe the performance viz: energy saving potential, Lux levels, and mean radiant temperature. Simulation using an energy model was conducted to estimate the annual energy savings. It is observed that retrofit hard coat low-e double glazing saves up to about 9% of daily energy consumption of Air conditioners (with annual average of 3% for Singapore weather conditions), when installed on all three sides (SE,SW,NW), for clear glass with window to wall ratio of 20% and air change rate of 1 ACH. For the same conditions the annual average energy savings can go up to 7.5% when installed on an existing grey tinted glass.