Pay your invoice with PayPal!
Pay your invoice with PayPal!
Accent By Masters News
Not just for heat control: How the right window film can enhance
By MARTY WATTS, V-Kool Inc.
Back in the good old days, window film was invented to reduce temperatures in buildings and homes. Too much solar energy entering windows increased heat, making occupants uncomfortable and air conditioning more expensive to operate. Window film was a simple solution for a simple problem.
Today the issues facing building managers and related decision makers are anything but simple, and extend beyond overheating and energy conservation. Today's indoor building management challenges include dealing with stale, under-ventilated and circulated air, moisture and mold growth, off gassing of furniture and building components, and the impact of such conditions on the productivity, health and well-being of building occupants.
Sick-building syndrome not only threatens building occupants, but also it can result in litigation that threatens the bottom line of employers and building owners alike.
Knowing how glass performs will make clear the role of window film in mitigating the ability of glass to negatively impact the indoor environment.
Unlike solid walls, windows and fixed glass allow the relatively easy transmission of both heat and light (as well as ultraviolet radiation) into a building's interior. Since glass in built and yet-to-be constructed buildings will continue to account for a significant percentage of a building's envelope, building managers and related decision makers must understand how glass performs in terms of heat and light transmission when developing and implementing a comprehensive strategy for managing a building's environment and indoor air quality.
Take the issue of heat, for example. According to the California Energy Commission, as much as 40 percent of a building's cooling requirements is from heat entering through existing windows. Reducing heat in a building is usually considered to be a legitimate and exclusive HVAC function.
As a supplement to HVAC, using heat-blocking window film not only reduces air conditioning operating frequency and cost, but also can placate many building occupants who believe "conditioned" air is less desirable to work or live in than non-conditioned air.
At Stanford University's Encina Hall, some 6,212 square feet of spectrally selective window film was applied in 2003. Spectrally selective film blocks solar heat while simultaneously transmiting high levels of natural light.
Daily air-conditioning (A/C) requirements to remove heat at Encina Hall prior to the film's installation amounted to 665.57 A/C tons, at a cost of $66.56 per day. Daily air-conditioning requirements to remove heat with the film installed are 339.44 A/C tons, at a cost of $33.94 per day. As a result of the film's installation, Encina Hall now enjoys an annual savings in A/C cost of $4,891.95.
According to the Common Colds Centre, Cardiff School of Biosciences at Cardiff University in the United Kingdom, air conditioning itself may contribute to infection with common cold viruses. The Centre's Web site contends air conditioners extract moisture from the air, causing drying of the nose's layer of mucus that protects against infection.
According to an internal study conducted by the ECOS Corp., "Intensive air conditioning all year long was identified as having a strong negative impact on the quality of the office environment."
Carpeting, glue used in furniture and various chemicals in building materials have a propensity to "out-gas," or release fumes, most of which are not healthy for building occupants to breath. Out-gassing is a function of molecular motion. As the temperature of a room increases, no matter what the source of that heat, those physical entities that are out-gassing will out-gas more.
It is not necessary to rely entirely on HVAC systems to reduce out-gassing by lowering temperatures when the application of window film can do much of the job, not only at a lower cost, but also without the necessity to subject building occupants to prolonged conditioned air.
The presence of mold is a function of moisture inside a building. Humid interiors will breed mold and the warmer those interiors become -- without actually reducing the amount of moisture -- the more hospitable the environment for mold formation and proliferation.
Reducing interior temperatures supportive of mold growth in humid environments need not depend entirely on HVAC systems. Less costly and more benign window film can shoulder much of the burden of interior heat reduction if that heat is caused by solar energy entering through windows.
If the point of window film is to reduce indoor temperatures without the need for extensive reliance on expensive and objectionable conditioned air, should decision makers opt for the window film that blocks the most heat? What seems the logical implication is not the right choice.
Tinted film blocks heat by absorption. Reflective film, which sometimes appears mirrored, reflects heat. Some of these films block heat better than others, but all, to one degree or another, are unable to transmit significant levels of natural light. In some cases, highly reflective window films with metalized heat-reflective coatings block as much as 85 percent of the visible light outside from entering the inside of a building. Why does this pose a negative impact to indoor air quality?
Conventional window film blocks so much natural light it darkens building interiors, often resulting in the need for additional artificial illumination that can often generate more heat. Ultimately, in many buildings, this requires the use of more air conditioning, which defeats the purpose of installing heat-reducing window film.
Additionally, the denial of natural light to building occupants negatively impacts their productivity and well-being. Studies conducted by the California Energy Commission, the U.S. Department of Energy, the Rocky Mountain Institute and the Lighting Research Center at the Rensselaer Polytechnic Institute document a relationship between low levels of natural light and less than optimum performance on the part of building occupants. Spending significant time in unnaturally dark spaces (and even spaces with adequate artificial illumination but limited natural light) causes people to feel less energized, often suffer more illness, take more sick days and be less productive than their counterparts in naturally illuminated environments.
Fortunately, it is possible to select window film that will block significant amounts of solar heat entering a building without reducing natural light. Spectrally selective film transmits natural light while blocking the heat that can exacerbate out-gassing, mold formation and sick-building syndrome.
No silver bullet
Knowledgeable decision makers responsible for establishing and implementing a comprehensive strategy for managing a building's environment realize that no single program component constitutes a silver bullet. In that regard, window film can no more do the job alone than can overburdened HVAC systems, which historically have been expected to carry 100 percent of the responsibility for maintaining a healthy indoor environment.
In reality, the quality of the indoor air and overall environment depends on several proactive initiatives undertaken by building decision makers. They include selecting furnishings and building components that will not out-gas and preventing the formation of condensation and humidity in sufficient amounts to cause mold. Most significantly, a strategy to manage a building's environment must rely on an adequate HVAC system whose ability to reduce heat is aided by the simultaneous implementation of appropriate heat-blocking window film and other relevant methods to both save energy and enhance environmental quality. Only when a multitude of systems function in an integrated and orchestrated approach will positive results be achieved and maintained. In such a program, window film will play an increasingly important role.
Watts is president and CEO of V-Kool Inc., a Houston-based distributor of spectrally selective and security applied window films.