PARIS – Charles de Gaulle Airport is one of the busiest in Europe and often is crowded. Such was the case last week. Although the outside temperatures were cool as the calendar moved toward November, it was cooking inside in the departure gate areas.
The reason for the unexpected heat was simple: The tube-line design of the terminal featured large swaths of glass that wrapped around the building. And piercing the unprotected glass were fierce rays from the unrelenting sun.
How hot and uncomfortable was it in the departure areas? Despite the overflowing crowd of passengers, most of the chairs exposed to the sun remained empty, as you can see in this photo.
It’s surprising – no, shocking – that one of the most recognizable airports in the world has not yet addressed such a basic issue as solar heat gain – especially with the energy conservation movement over 50 years old.
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 between film and windows 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.
In new building construction the choice between solar control film and shaded windows is more complicated.
Still, in this day and age, there’s little excuse for building owners not to make their buildings more comfortable – and energy efficient – by installing solar control window films or some other method.
In particular, places where large number of people gather, such as airports and convention centers, have a significant incentive to install energy efficient solar control window films.