Commercial and residential buildings in the tropics use 50 to 70 percent of their energy consumption for comfort cooling. A sizable portion of the cooling demand is often due to heat gain through glazed areas (windows, skylights and atria). In many countries, Demand Side Management is being implemented to ensure that buildings incorporate energy efficient green technologies like window films.
Clear glass permits almost all of the sun's direct radiation to enter. Tinted glass absorbs part of this heat and re-radiates it to the room offering limited heat protection. However, daylight level drops very low, with the use of tinted glass. Blinds and draperies block the sun's light, after it has entered the building. The heat absorbed is then re-radiated into the room. This radiant heat input may be 5 times greater than the heat being conducted from the warm outside air. Solar control films bounce away up to 70 percent of the heat normally transmitted by the sun into a building through the windows.
Recent advances in thin film coatings for window glass products provide a means of reducing heat gain significantly without proportionally reducing daylight transmittance. Because of its impact on both cooling and lighting loads, the choice of glazing for windows and skylights often represents the most significant design decision affecting energy use in commercial buildings. A good design consideration of a glazing system entails the use of daylight as a lighting source, provides exterior aesthetics and controls excessive solar heat gain.
The increasing trend of constructing high rise commercial and office building, with large glass areas and light weight panel walling, has given a boost to the demand of air conditioning in tropical regions. As such, the objective for energy conservation must be the promotion of efficient use of energy through better design and more energy efficient system.
The same energy efficient principles also apply to the design of new generation automobiles. To achieve greater all-round visibility, better aesthetics and lower wind resistance, glass windshields in vehicles are designed to be larger and more sloping. This means greater heat gain into the vehicles requiring larger compressors for rapid cool down. The Visible Light Transmission regulation for vehicles is normally standardized at 70% and more. Reflective coatings are not permitted while lightly tinted glass often does not protect the occupants from the intense heat of the sun. Spectrally selective coating are not being incorporated into OEM windshields by premier European car manufactures to block off heat, thereby increasing thermal comfort while reducing energy consumption. The clear heat control film also complies with law without posing safety and security risks associated with dark tints.
Originally developed for the US space and military program, and now being adapted for commercial use, V-KOOL® is a transparent, infra-red reflective polyester film which can be bonded to glass surfaces, The polyester is coated on one side with multi-layers of microscopic metal particles, and a pressure sensitive adhesive on the underside.