Key design features of multi vacuum glazing for windows: A review

The use of vacuum glazed windows is increasing due to their application in modern building design. Among various types of vacuum glazed windows reported in literature, thermal transmittance of single glass sheet (conventional window) i.e 6 W/m2k is reduced by 66 and 77% using air filled double glazed and air filled triple glazed windows respectively. Using low emittance coatings thermal transmittance of double glazed windows is reduced by 53%, however it offsets the visibility by reducing light transmittance by 5%. Stresses due to temperature/pressure gradients if not eliminated may lead to reduction in service life of vacuum glazed windows. Vacuum created between the glass sheets is used to reduce conductive heat transfer. Degradation in the vacuum is caused by number of factors such as, permeation of gaseous molecules through glass sheets, leakage through sealing, thermal/optical desorption and photo-fragmentation of organic species have been critically reviewed and future trends are outlined