Windows are a key element to many structures. They can also be a major cause of heat gain during the summer months, and loss in the colder seasons. Fortunately, there are many ways to increase the energy efficiency of these all-important features. By utilizing tried and true techniques, as well as state of the art technologies, it is possible to greatly improve performance without impairing the primary function of the window, visibility.
One major source of inefficiency, especially in the summer, is air flow. Highly efficient windows have a near perfect seal, only allowing for circulation when opened. Achieving this can be accomplished in several ways. It is, of course, necessary to understand where the opportunity for wastefulness can occur.
The most likely area is in the frame, and where the panes of glass join it. Older frames were generally constructed of wood and, due to their nature, would expand and constrict with fluctuations in temperature and humidity.
More recent fabrications utilize many other materials, such as fiberglass, vinyl and various metals. While painting and sealing wood frames can augment their function, it is unlikely that an older frame can attain the efficiency of these newer materials. That is not to say, however, they are unilaterally worse than the alternatives.
Metal frames conduct heat more easily and can be a primary source of loss and gain not associated with air circulation. There is also the cosmetic aspect that must be considered, many people do not find artificial components to be as visually pleasing as a natural wood. Finding a balance between efficiency and aesthetics is vital.
Another area that can affect heat transference, as previously mentioned, is conductivity. Wood frames are relatively effective for reducing flow, though insulated fiberglass and vinyl are the most efficient. Not only associated with the frame, the glass itself is a major point of potential movement. This issue is largely mitigated by the use of double, or even triple, paned glass.
An older development, originating in the early twentieth century, there have been significant improvements since. The basic concept is constructing the window with a small air space in between the panes of glass to allow for a more effective insulation. Newer developments include the introduction of inert gases, usually argon or krypton, which have a higher resistance to heat flow than air.
The most recent developments for increasing the efficiency of windows is by applying various tints and coatings to the glass. Using reflective tints can greatly reduce the amount of light, and consequently heat, that travels through the window.
This is most effective in warmer climates and seasons, when heat gain is the primary issue, and unfortunately also affect transparency. Latest advancements are in the use of spectrally selective applications, these utilize materials that filter solar radiation by type. By excluding only infrared light waves, which carry the majority of the heat, they effectively inhibit transference without affecting visibility.
Maintaining and updating windows is an important and effective way of increasing the energy efficiency of our homes, and can often be accomplished with little effort and cost.