Global technological advancement and challenges of glazed window, facade system and vertical greenery-based energy savings in buildings: A comprehensive review

There are many factors that have a major influence on reducing the energy expenditure in building sector. This research aims at qualitative and quantitative assessment of those factors such as double glazed windows, vertical greenery systems (VGS), integrating of semi-transparent photovoltaic device with architectural design of buildings, energy saving by using heat reflecting coating, passive climate control methods, energy saving by shading, building energy performance enhancement by using optimisation technique, double skin green facade, etc. through a holistic and thematic approach. Amongst the aforesaid techniques, VGS is found the most reliable, efficient and sustainable solution. Attractive VGS can improve the urban environment, increase biodiversity, mitigate pollution also results economic benefit of the buildings as like as energy savings and decreasing surface temperature. Four fundamental energy saving methods are used in VGS which are considered as passive energy saving mechanism. Firstly, interception of solar radiation due to the shadow risen by the vegetation; secondly, vegetation also provides thermal insulation; thirdly, plants evapotranspiration helps for evaporative cooling of building; finally, building blockage makes a variation of wind effect on building. The peak cooling load of ivy coated green building wall has been reduced by 28%. If a VGS is installed without windows and building facing on west, east, south and north correspondingly, the reduction in the cooling load capacity of the building is observed to be up to 20, 18, 8 and 5%, respectively. Very high thermally resistive glazed areas on building envelope can be secured via thin film PV glazing and vacuum glazing products with an average U-value of 1.1 and 0.4 W/m2K, respectively. Energy use policies are also helpful to improve energy consumption scenario of buildings. For developing more energy-efficient, sustainable and eco-friendly buildings, these techniques might be helpful for the building designers and architects.