09 June 2009
To many facilities managers, window film can be likened to the ‘utility’ player in a football team. It can play a number of roles and solves a multitude of problems.
It was, of course, introduced in America in the 1960s to reduce glare and heat transmission problems particularly in high-rise office blocks. Fast-forward to today and modern high-technology window film is able to make a major contribution to two issues which are very much twenty-first century. Because window film can now significantly reduce a buildings' carbon footprint whilst at the same time providing healthy levels of natural day light.
Over the years window film options have been developed that reduce the risk of injury following glass contact accidents, and when the workplace regulations introduced in 1996 stipulated that glass in risk areas had to meet British Standard 6206, it was window film that upgraded the majority of existing glass to comply.
During the excesses of terrorist activity through the decades it has been high-tensile strength window film that has provided protection from flying glass – the cause of 90% of serious injuries.
In the 1960s window film transformed glass into mirrors. The heavily metallic film literally reflected the suns' rays away but at a cost to the aesthetics of the building. The old style mirror-like film would be less acceptable today but it was the research and development into alternative technologies that created the additional major benefit to be gained from the latest window films.
These days window films are available that reduce to acceptable levels transmitted glare and heat and yet have very high visible light transmission properties. These films are beginning to be used extensively in areas like education and business where the requirement is for good natural daylight but without the negative aspects of the sun.
The last decade has seen a dramatic increase in the use of architectural glass, which has exacerbated problems of heat gain and glare. In the same period there has been a consistent growth in the use of air-conditioning. Today it is facilities managers who are tasked with remedying the problems created by the combination of large expanses of glass and air-conditioning. The major issue with this scenario is that the glass allows the excesses of the sun into the building which then has to be cooled down by air-conditioning.
Quite correctly, air-conditioning has come under the microscope as it has become evident just how energy inefficient a way of controlling temperate it is. According to the Building Research Establishment (BRE), solar gains in a glazed building can account for ten times the heat generated by equipment or lighting. It’s not just glazed buildings either, a window representing 40% of wall space on a South facing elevation can transmit 63W of heat to a square meter of floor space.
Whereas the Carbon Footprint focus had previously been on heating, now it has set its sights on the hot summer months and the cost of cooling.
Ironically the window film industry has been banging this drum for some time. Their argument is that it makes no sense to allow the heat into the building only to have to cool it down. Particularly as modern solar control window films allow high levels of natural light through whilst keeping the excesses of the sun out.
The cost of heat gain can be counted in many ways. The wasted energy used to disperse warm air is the more obvious cost. The cost to the environment created by unnecessary emissions is another. Add to that the reduction in productivity created when temperatures rise, as evidenced by a research study in the USA by Wyon, albeit some while ago, which found that productivity in an office environment dropped by 40% at 75°F compared to 68°F, the most comfortable temperature to work in. Other research from the USA by Vernon found that accidents are 30% more likely to occur at the higher temperature because people become fatigued. Finally, glare from the sun falling on monitors is also a problem with 75% of people that work on computers suffering from some kind of eye strain.
So efficient is the performance of modern window films that some have better solar protection properties than any available glass. The argument for window film and against excessive use of air conditioning is increasing at the same time as the daytime temperature is rising. An Energy Audit which measures not only the savings as a result of installing solar control window films through the reduction in energy consumed by air conditioning and cooling devices but also the reductions in CO2 emissions, is available for any interested organisation. For a typical air conditioned building these audits show a pay-back from solar control window film in under five years.