Have you ever felt your window as cold as ice during the winter or burning hot during the summer, while your heater (or air conditioner) is operating at full blast? If so, you are definitely throwing money out the window ! Consider making changes on your existing window, before you have to sell your heater (or A/C) to pay for energy bills.
Window technology has improved dramatically in recent years because of the conscious effort to save on energy. Below are some of the features to improve the thermal efficiency window.
Gone are the days when a window is made up of a frame, a glass pane and a latch. Today, energy-efficient window-designs require a minimum of two (2) layers of glass, called double-glazed windows. Double-glazing insulates almost twice as well as single glazing (single glass pane). It is also possible to add a third or fourth layer to further improve the results. Some of these windows use clear glass only; others opt to install additional layer of thin plastic films for tinting as well as further insulation.
2. Thickness of air space.
In between the two glass panes in a double-glazed window is a space filled with the air. With a thicker air space, the window will be better insulated because it will have a better transfer of heat. Thicknesses range from ¼ ” to 1”. If the air is wider than 1”, however, there is no further gain in performance.
3. Type of air in the space.
Traditional double-glazed windows were filled with air or flushed with dry nitrogen to ensure that the air does not leak. In a sealed glass pane, heat is carried to the top of the air space while cold pools settle at the bottom. By filling the space with a less conductive gas like argon (Ar), carbon dioxide (CO2), krypton (Kr), and argon-krypton mixtures, the overall transfer of heat between the inside and outside is reduced. It should be noted that the thickness of the airspace also depends on the kind of gas that is used to fill it.
4. Edge spacers.
What holds the panes of glass apart are the edge spacers. These also provide the airtight seal in the window. Before, hollow-aluminum channels filled with desiccant beads were used as edge spacers. Since Aluminum is a highly conductive material, heat loss (or gain) is now occurring through the edges. Improvements to the material used include thin-walled steel with thermal breaks, or silicone foam or butyl rubber. A low-cost option when ordering windows would be to consider insulating edge seals with traditional aluminum spacers.
5. Low-E coatings.
Low-emittance (Low-E) coating are very thin, metal or metallic oxide layers set on a window glazing surface primarily to improve the heat transfer (reduce the U-factor). Heat is transferred in multilayer glass from a warm pane to a cooler pane. With a low-emittance coated material facing the air space between the glass layers, it blocks a significant amount of heat transfer, thus reducing the total heat flow through the window. Different types of low-e treatment are now available for different climate zones and different applications in any particular location.
Enough about the glass pane, let’s now focus on the materials surrounding the glass, the window frame. Different kinds of materials can be used for the encasement, depending on aesthetics (suits the design of the home), durability (resistance to storm, wind or extreme weather) and, of course, energy efficiency (U-factor).
Metals (aluminum, or light metal) for example are lightweight and easy to clean, but conducts heat rapidly. If metals must be used for window frames, ensure to place insulating material between the inside and outside of the frame and sash.
Wood (natural and composite) have better thermal properties, but must be treated for moisture and termite decay. Natural wood also contracts and expands through weather changes and can be heavy and thick, thus reducing the view and light passing through.
Plastics (fiberglass, PVC, vinyl) have the highest thermal resistance as compared to the previous, especially if treated with insulation. It has good moisture resistance and need no painting because color treatment is already incorporated in its production. However, at extreme temperatures, they may expand, warp or crack. Also, if exposed to sunlight for long hours, colors tend to fade over time.
Lastly, here are simple steps to ensure you are buying an energy-efficient window:
a. Look for NFRC label as your guide to energy performance (U-rating) and to suit your climate, before buying a window.
b. Choose windows with good warranties against the loss of the air seal. If the glazing seal is lost, not only will fogging occur, but also any low-conductivity gas between the layers of glass will immediately be lost.
c. Hire only skilled contractors to install your new windows. This will ensure that they will perform as well as they should.
What else are you waiting for? STOP throwing money OUT YOUR WINDOW!
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