Energy efficient glazings: Stimulating Eco-windows

Windows being an indispensable architectural element provide an essential link between the internal and external space of a building, facilitating the necessary barrier against the vagaries of nature. The triumphant design of a window depends on various factors including ventilation, controlling thermal insulation, improving lighting and climatic conditions within the building. Mostly all conventional windows use clear glass as glazing and grant only a certain level of energy optimisation. However, as the world moves to greener options in all walks of life, it is imperative to find glazing solutions with better, more efficient energy usage.

Windows may be constructed with compound glazings from two to three layers, depending on the climate type. These windows offer a heat barrier through insulation air cavity sandwiched between glass layers and are known as IGUs (Insulating glass units).

The idea behind energy-efficient glazings is to more effectively used to control the access of solar heat and light into the buildings. All solar apertures are now facing similar choices in their glazing. Contemporary conservatories too use a number of technologies to ensure that the glass is as energy-efficient as possible, ensuring that it allows maximum light in, and maintains a steady ambient temperature throughout the seasonal variations. These options include thermal breaks or thermal ribbons, argon-impregnated glass, or heat reflective metallic film. Metallic films are deposited on glass or polymer substrates with material combinations and coatings, contributing in the development of unique products. 

Also known as tinted glasses, these can substantially reduce the glare and excessive sunlight to penetrate into the building. Designed basically through an admixture of metallic oxides the solar radiation absorbed by the glasses can cause heat gain in the interior of the building. The detrimental effect can be eliminated by adding an inner clear glass to prevent the heat radiation to flow to the interior of the building.

Thin coatings of pure metal like gold, silver or bronze between the two layers of glass are applied providing low transmittance of solar energy with high insulating efficiency. The reflective property of these microscopically thin coatings can significantly diminish the transfer of solar radiation both heat and glare in a hot climate.

Unique optical coatings of low emissivity are applied to glass or plastic glazing materials to reduce the radiative heat transfer either from the outside of the building to the inside for hot regions or from the inside of the building to the outside for colder regions. The newly developed glazing options are gaining popularity in countries like Japan, USA and Europe facilitating energy and light controlling properties to the windows.

The energy performance of a window with advanced glazings can transform energy liability of the buildings to  energy assets. This would not only offset the higher initial investment for the glazings being used but would also have a longer- term environmental benefits due to reduced energy consumption and lower amount of chlorofluorocarbons - and that's the way ahead for a greener future!