The use of glass dates back thousands of years, with its popularity rooted in versatility and the ability to provide shelter while allowing sunlight in.
Since the flat glass process revolutionised glass manufacture more than 60 years ago, the material has become increasingly common, but today, there is an unprecedented obsession with glazing that allows maximum vision and sunlight in modern architecture. But while vision and sunlight is perceived by human beings as positive, the impact on the building tells a different tale.
From weakness in the overall structure, to the risk posed by fire and explosion, it is important to balance the use of glass intelligently and position it where it matters most. For example, in an apartment window in the living room is essential but don’t need to be designed for all rooms. We need to incorporate other interior design elements such as curtain size and type before designing wide-angled windows.
Today, the UAE has a glass to wall ratio often exceeding 60% in office buildings and 40% in residential buildings while most international codes set a limit of 40% and 20% respectively. In addition most buildings facades are identical from all four sides irrespective of external view or impact on heat load, which facilitates the architect’s work in creating similar details for all facades.
Glass facades cost around $400 per metre squared while walls with epoxy finish cost around $150 per metre squared, and walls with aluminum cladding cost $200.
Double glazing has a U-factor (the overall coefficient of heat transfer) of 3.7 times higher than insulated wall, but transmits on average nine times more energy that combines temperature transmission and sunlight, which is absorbed by internal surfaces (see table).
The majority of architects are shocked when they read this fact and commonly assume glass would only transmit 3.7 times more energy, because they haven’t accounted for the impact of light transmission through glass. The transmission is absorbed by the ground slab, where it is stored as heat and released over several hours, sometimes way past midnight.