Energy efficiency is the main plank of the current EU energy policy. The building sector has become the focus for delivery of energy efficiency targets as it accounts for over 40 percent of energy demand.
“Windows connect building interiors with the outside world and are therefore responsible for a large amount of the energy use within buildings,” noted Valérie Hayez Strategic Application Engineer/Technical Service with Dow Corning Corporation. “To minimize the energy consumption of buildings, it is increasingly important to choose energy efficient windows.”
Energy Inefficiency of Windows
Windows are responsible for a disproportionate amount of unwanted heat gain and heat loss between buildings and the environment. In Sweden, seven percent of the total national energy consumption is lost through windows and in Britain this figure is six percent for residential buildings alone.
Energy-Related Performance Challenges for Windows
There are three key energy-related performance challenges for windows:
- to control heat loss in cold months;
- to allow daylight into interiors, while maximizing solar heat gain in winter and minimizing it during summer; and
- to minimize heat loss from air infiltration through windows.
Independent Validation for the Selection of Energy Efficient Windows
Selecting energy efficient windows used to be difficult due to the lack of independent and validated information. In 2001, eight European countries came together to create the European Window Energy Rating System (EWERS), with the intent of helping consumers, retailers, architects, building owners and others choose the most energy efficient windows for their projects. While the EWERS labeling system has not developed into a uniform pan-European window rating system, various national initiatives have sprung from this program, such as the British Fenestration Rating Council (BFRC) labeling system. These national initiatives are the forerunners of a Europe-wide network of compatible window energy rating schemes that will facilitate the free transfer of information across European borders.
“This information not only helps inform window consumers, but it creates an incentive for window manufacturers to improve the performance of their products,” said Andreas Wolf, Scientist for the Global Construction Industry at Dow Corning. “Ultimately, this should lead to an increased amount of high-performance windows installed in Europe and, as a result, to a reduction in energy use and carbon emission in buildings.”
Structurally Bonded Windows
An emerging technology has broken new ground in improving window performance while allowing for the innovative structural use of glass. Structurally bonded windows constructed with silicone sealants transfer the load from the frame to the glass while accommodating movement between the frame and glass that occurs due to differences in thermal expansion between the materials. This increases the structural strength of the window, allows for leaner and more slender frame designs and increases the window sizes that are possible. In addition, structurally bonded windows, depending on their specific design, may help improve the thermal performance of the window as well as improve its protective properties, such as enhancing resistance to burglars, explosions, extreme weather events and earthquakes.
Benefits of Structurally Bonded Windows
“These windows offer several benefits to builders and home owners, including increased daylight and better thermal insulation,” said Hayez from Dow Corning Corporation. “They also help companies improve their productivity while reducing costs during window manufacturing.”
This information has been sourced, reviewed and adapted from materials provided by Dow Corning.
For more information on this source, please visit Dow Corning.