Historically, window film has been used to reduce temperatures in buildings prone to overheating. Too much solar energy entering through windows makes occupants uncomfortable and air conditioning more costly. Film has been a simple solution for a simple problem.
But the environmental issues facing school buildings extend beyond overheating and energy conservation. Many measures intended to increase energy efficiency — such as “tightening” buildings to reduce air infiltration and outflow — have led to negative impacts on indoor environmental and air quality. Sick-building syndrome threatens building occupants and can result in costly lawsuits.
School building designers must address issues such as under-ventilated and circulated air, moisture and mold growth, offgassing of furniture and building components, and how such conditions affect the productivity and well-being of students, faculty and staff.
Windows and fixed glass allow the relatively easy transmission of heat and light into a building's interior. Glass will continue to be a significant part of a school building's envelope because daylight has been shown to improve student performance and well-being. Architects and facility managers should understand how glass performs in terms of heat and light.
For instance, according to the California Energy Commission, heat entering through existing windows accounts for 30 percent of a building's cooling requirements. Reducing heat in a building usually is considered to be an HVAC function, but stopping heat at the window with heat-blocking window film can reduce air-conditioning costs, and placate many students and staff who believe “conditioned” air is less desirable than non-conditioned air.
At Stanford University's Encina Hall, about 6,212 square feet of spectrally selective window film was applied in June 2003. Spectrally selective film blocks solar heat while transmitting 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 an A/C cost of $66.56 per day. Daily air-conditioning requirements to remove heat with the film installed are 339.44 A/C tons at an A/C cost of $33.94 per day. As a result of the film's installation, Encina Hall is seeing an annual savings in A/C cost of $4,891.95.
Anecdotal evidence suggests that air conditioning aggravates the effects of arthritis and neuritis, and makes some people sick because of the extreme variances between outside and inside temperatures.