How Solar Control Window Films Have Made Office Buildings More Energy Efficient

Solar control window films help reduce the amount of harmful UV rays that penetrate clear glass windows in office buildings, making the areas near the windows more comfortable for employees. The film also reduces solar heat gain, which can throw a building's HVAC system out of whack through uneven building temperatures.

The idea of energy-efficient, green office buildings is so common today, people forget it hasn't always been this way. It took an oil embargo in 1973 by the Arab members of the Organization of Petroleum Exporting Countries [OPEC] against the United States, which tripled the cost of oil prices and gas, to trigger a move toward more efficient technologies.

In older office buildings, that meant installing more efficient HVAC systems, adding insulation, improving the lighting, finding and closing up air leaks and addressing the windows issue, which was significant.
We all have sat next to windows in buildings where sun rays entering the space, while seemingly nice on cold winter days, can in fact be brutally warm. Not to mention the glaring issues it causes. The result is a comfort issue for office employees with desks near windows.

The larger problem was the impact the intruding rays of the sun had on a building's HVAC system. In winter, hot rays from the sun intruding into the building can fool the HVAC sensors, making it seem like summer. As a result, the A/C can go on. Employees near the windows are no doubt happy but the rest of the people in the building are not.

This sun control situation caused energy bills to climb at a time when they needed to decline because of the sharp rise in oil prices and other energy costs. Yet another issue with solar heat gain was its effect on artwork, furniture, carpet and other furnishings. Over time, the sun's rays caused the artwork and furnishings to fade, resulting in permanent damage. This was especially true in art museums and libraries.

So, there was a need for a product that would solve all these issues dealing with office building windows, in particular the energy costs.

Solar control window films arrive

Window tinting companies had been around for some time, but their focus was on the auto industry, especially in hot climates. But soon after the oil embargo was lifted window tinting and film companies developed a special film for office building windows helped control the impact of the sun's rays entering the structure.

The specialty solar control film was developed to counteract or even out the solar heat gain. The scientific aspect of this relates to what's known as the Solar Heat Gain Coefficient. This measures the solar heat that enters a window and becomes heat. There is a measurement between 0 and 1 that accurately measures the solar heat gain. The lower the number, the less heat is being transferred.

Another factor is U-Value. This measures heat transfer related to outside and inside temperature difference. HVAC engineers and insulation professionals use R-Value, which measures window film's ability to act as an insulator. The higher the R-Value, the less the heat transference.

The final key component of the analytic process is the Shading Coefficient. This a comparison analysis of an untreated window and window that has solar control film attached. The lower the shading coefficient, the better the shading performance.

So, over the years, the expertise of solar control film manufacturers has increased dramatically. The variety and effectiveness of sun control window films have improved as well.

Solar control film vs shaded windows

From the beginning, the overriding issue was cost. There were a number of factors in play:

  • Cost of the solar control window film and installation

  • Cost of solar control film vs installation of energy efficient windows

  • Length of time it took for the solar control window film to pay back the company's investment via energy savings

  • Length of time the solar film lasted before having to be replaced

In older buildings, solar control window film always has been the most cost-effective option. Generally, the payback period via energy savings is around seven years. The warranty on most films is around 15 years and the film can last longer.

New window installation in an old building is cost-prohibitive in most cases, unless a total renovation is in order. Payback on new windows through energy savings is a considerably longer period versus solar control window film.

Another factor is the installation process. Companies who try and cut corners by selecting an inexperienced film window film installation company often end up paying more in the long run. If the film is improperly applied to the office windows it will be not be effective. The industry is filled with stories of companies having to hire a second, more experienced installation company to first remove the improperly installed solar control film and then installing new film.

High profile solar control window film projects by CWS

Some of the more high-profile solar film installation projects over the years cover different needs were:

Willis [former Sears] Tower, Chicago: The building had sun control issues impacting its HVAC system

Walter E. Washington Convention Center, Washington, D.C.: The building had an issue with solar heat gain, glare and fading issues with furniture, carpet and artwork.

National Gallery of Art, Washington, D.C.: One of the country's most famous galleries faced sun issues that were damaging priceless paintings.

Yale University Beinecke Rare Book & Manuscript Library, New Haven, Ct.: The library's rare book collection was at risk from the glare of the sun entering through unprotected windows.

About the Author

George J. Tanber is a freelance journalist specializing in the window film industry and international affairs. He is the publisher of

Featured Product

HPS EnduraCoilTM Cast Resin Medium Voltage Transformer

HPS EnduraCoilTM Cast Resin Medium Voltage Transformer

HPS EnduraCoil is a high-performance cast resin transformer designed for many demanding and diverse applications while minimizing both installation and maintenance costs. Coils are formed with mineral-filled epoxy, reinforced with fiberglass and cast to provide complete void-free resin impregnation throughout the entire insulation system. HPS EnduraCoil complies with the new NRCan 2019 and DOE 2016 efficiency regulations and is approved by both UL and CSA standards. It is also seismic qualified per IBC 2012/ASCE 7-10/CBC 2013. Cast resin transformers are self-extinguishing in the unlikely event of fire, environmentally friendly and offer greater resistance to short circuits. HPS also offers wide range of accessories for transformer protection and monitoring requirements.