While low-e glass prevents heat from leaving a building, many times the cost of heat entering the facility is completely neglected. That’s what energy control films regulate. (Shutterstock photo)

Particularly in the hotter months, energy control film, aka window film or solar window film, proves to be an economical solution when it comes to reducing energy costs, especially for municipalities coping with the operating expense of aging infrastructure. In fact Marcus Billings, architectural consultant for Scorpion Window Film describes window film as “the number one retro-fit application in terms of monetary savings most buildings can purchase.”

Energy control films are designed to improve the performance of windows — the weakest section of the curtain wall in terms of insulative properties — without the time and cost needed to replace them.

“Most non-residential buildings built from the 1950s to the 1990s were built with very simple glazing systems,” noted Billings. “Most of these structures ended up with glazing that has poor insulative properties. Even buildings that have had their windows replaced, probably switched from single pane clear to double pane clear. Low-e glass is often heralded as the premier glazing system, but unfortunately, it does almost nothing to stop the most costly glazing problem there is: solar heat gain.”

Solar heat gain reduction is one of the main reason window film is particularly popular in the southern half of the country. Local governments in California, Arizona, Texas, Colorado and so on have all put energy control film to the task. An early adopter, Denver, Colo., notably used solar film with low-e properties to retrofit its portfolio of buildings, leading to significant energy savings and improvement to the bottom line of the city.

“Sixty square feet of glass exposed to direct sunlight admits 12,000 BTUs of heat per hour during the summer,” Billings said. “It takes one ton of air conditioning to offset. This is why so many buildings have ‘hot spots’ that necessitate extra measures to cool problem areas.” He added energy control films can reduce the total solar energy experienced by as much as 85 percent.

“Again, most energy savings ideas are directed at winter times savings and the heat that escapes from a building. That is an important issue, but many times the cost of heat entering the facility is completely neglected. This is what energy control films do so well.” Low-e glass only helps with the radiant heat leaving a building; it does not keep additional heat from entering a building. “Many municipalities that have installed new low-e glazing believe that they have reached the end of savings that they can experience with their glazing; this isn’t true,” Billings added.

And window film provides other benefits besides energy savings. Bo Ryan, vice president of Performance Films Distributing, noted, “In addition to improving the energy efficiency of the portfolio of municipal buildings and reducing run rates, the retrofit of solar films will also enhance the building aesthetics, protect capital investments, improve employee safety and comfort, and exhibit corporate commitment to sustainable practices.”

Film creates a deepened tone on existing glass that obscures the view of partially closed blinds, interior furnishings and items placed in window sills while also creating an uniformed appearance for the buildings. Employees and visitors reap benefits as well with the reduction of not just solar heat gain but glare; this reduces eyestrain through improving visibility of both electronic monitors and printed material. Films like those used by Performance Films Distributing also block out 99.9 percent of harmful UV radiation, a significant contributor to diseases of the skin and eyes. Items in the buildings, such as carpet, furniture, electronics and artwork, are also protected against UV radiation by window film, which can increases their lifespan.

“Solar films mitigate potential injuries in the event of failed glass from windstorm, spontaneous failure or human impact,” Ryan stated. “Potentially hazardous glass shards are retained by the solar film.”

Billings stated buildings of all sizes, including thousands of municipal buildings throughout the world, have used window film. “The Willis Tower has used energy control film since its completion to maintain costs and keep tenants comfortable.”

Many school systems and local governments have adopted the installation of film, too, and frequently combine this retrofit with lighting upgrades and technologies that improve the insulating capacity of building envelopes. An energy analysis can be performed for each potential retrofit with a financial realization prepared for the city government.

“These studies are done as a free service to the city. The harvesting of available rebates will be explored for each city increasing the financial realization of each project,” Billings said.

Depending on the percentage of glazing versus building square footage, a facility can save between 15 percent and 40 percent of its normal cooling costs every year by adding energy control film. With a normal payback time of 1.5–4 years, the savings are realized for years and years to come.