Energy performance Films

Window film can contribute to a considerable reduction of the energy bill both in summer as in winter time.

There are window films on the market that allow improving the thermal insulation of a glazing, when applied professionally.

These products, generally referred to as low-E films (E stands for emissivity) can improve, the thermal insulation value of the glazing of a window.

Global Warming European Union Viewpoint

Global warming from carbon dioxide emissions and the cost of energy are major topics of discussion around the world. The European Union and European Governments are committed to reducing carbon emissions and improving energy usage with a particular focus on energy in buildings. In 2007, the European Commission organized a conference on the best implementation of the Energy Performance of Buildings Directive in the context of the EU sustainable Energy Week and identified energy efficiency in buildings as the most decisive contribution to improve energy efficiency. Energy efficiency in buildings is also at the heart of the Energy Efficiency Action Plan published by the Commission in October 2006 and part of the Strategic Energy Review presented in January 2007.

The Growth in Air Conditioning

In the ten years to 2000, Germany had a 250% increase in air conditioned floor area and the UK about 60%. The number of air conditioned buildings continues to rise across Europe. It is important to note that cooling buildings often consumes significantly more energy than heating. All this is in addition to energy demand caused by the revolution in computer and communications technology. The escalation in demand for energy adds to the attention given to energy efficiency. The most obvious source of high temperatures in buildings is the energy from the sun. In fact research by the Building Research Establishment (BRE) in the UK shows that on average, 40% of the load placed on air conditioning in offices comes from direct solar gain through windows. The cost of fuel means such sources of energy consumption cannot be ignored.

The Business Perspective

Responsible employers want to play a part in reducing global warming, and, naturally, they also want to keep staff happy while controlling capital expenditure and operating costs. In addition, European businesses and other organizations are required by EU Directive and legislation to maintain workplace comfort for employees, including ensuring temperatures in workplaces are neither too hot nor too cold - and energy is expended in cooling or heating buildings. This creates an apparent contradiction: save energy according to legislation or expend energy keeping workers comfortable according to legislation.

The Solution

Using modern high technology solar control window films, the cooling loads demanded by air conditioned buildings can be substantially decreased, giving business managers the possibility of significant savings in energy costs and maintain workplace comfort, as well as contributing to reducing carbon dioxide emissions.

Solar Control Window Films Performance

The fundamental requirement is to ensure the solar control window film reflects high levels of solar radiation back to the outside, before this solar energy can be absorbed by or enter into the building. Table 1 gives just a few examples of the performance of some solar control window films compared to selected glass types. With g values’ of as little as 1/4 that of the glass itself and total solar energy rejection values as high as 81% the solar control performance of glass can be improved considerably.

This shows that the range of solar control window films work well for various types of glazing. Typically, the metalized films, using aluminum, copper and silver, along with certain specific spectrally selective films have higher performances. Neutral films, using nickel or stainless steel, have more moderate performance and are more suited to clear glazing and older style buildings. External solar control films also provide high performance protection and can be used on virtually any glazing type.

Solar Control Window Films Payback Time

So what is the typical performance of solar control window films in reducing energy costs? Understandably, the actual results depend not only upon the film selected but also upon the glazing specification and building construction. However, it is possible to save thousands of Euros a year in energy costs, even in moderate climates. Payback times of less than 3 years are achievable.

How do I select the best film?

There are specialist window film installation companies across Europe to provide assistance in window film specification. These experts must understand glass and glazing as well as the window film itself. They will check your glass / glazing and ensure that the correct product is specified with respect to both your requirements and to the glazing system. They may even be able to provide a model for your cooling energy demand and an analysis of the predicted energy savings compared with current use, based upon the internationally recognized DOE-2 simulation software.