Selecting the Correct Window: Efficient Characteristics

So, what are defining efficient characteristics of window types? The main distinctions in windows include the number and type of glass panes, as well as any coatings on the glass pane.  

Single and Multiple Panes

Your traditional old-style window is a single pane of glass. This single layer of glazing isn’t very good at keeping the heat out and the cold in here in Bryan-College Station (or anywhere for that matter!). This low thermal resistance means that heat is entering your home, making you less comfortable, and causing you to turn your A/C on even higher! This is why it’s a good idea to upgrade your single pane systems to higher efficiency windows with more layers of glazing. Double pane windows mean there are two layers of glass with a sealed space in between. This space includes air or gas (such as argon) and acts as an insulating barrier to stop heat from entering or escaping through your window. There are also triple or quadruple pane windows that have three and four glass panes with gas filled spaces. To try to reduce the bulk of these windows there has been experimentation with thin plastic instead of glass panes. Although these triple and quadruple panes do in most cases insulate to a higher level, you can get just about the same savings and efficiency with a double pane window for your home.

Glass Coatings

Multiple pane windows also can come with what is called a low-e coating. This means they have a micro-thin coating of transparent metal on one surface of one pane of glass that helps to block heat transfer and loss. This is a characteristic that really increases the efficiency of a window, helping to keep the interior surface of the window cooler in the summer and warmer in the winter. This decreases heating and cooling loads, keeping your home comfortable without as much energy waste. Low-e coatings can also help to block UV light which reduces fading in furniture and other household items. Glass in windows can be tinted or have a tinted film applied to them that reduces heat gain, but this has some drawbacks. Tints can darken a space by reducing the amount of visible light let through the window or by adding a color to the light. Tints can also absorb heat during the summer which cancels out its purpose of reducing heat gain. This makes low-e coated windows an overall better selection for homes.

Multiple Pane Spacer Materials

Multiple pane windows require a spacer bar between panes of glass. This bar material is normally aluminum. Because this material doesn’t insulate well and can cause condensation in the window, other options are being explored. These “warm-edge” spacers are made from lower conductive metals, plastic, and even foam—all help increase the U-Factor of the window system, meaning a decrease in heat transfer.

With this knowledge, you can have confidence when selecting efficient windows. For even more information, see yesterday’s blog about NFRC and Energy Star labels. But be sure to do as much homework as you can. Find out about warranties offered by manufacturers to help with a long term perspective of upgrading your windows.