When you’re shopping for new replacement windows, energy efficiency is probably one of your main considerations. As well it should be, because improved energy efficiency equates to lower heating and cooling bills and a smaller environmental impact. But once you start looking into energy efficient windows, you’re met with a dizzying array of new terms and acronyms, and making sense of these is the key to making the right choice for your family, your home and your new windows.
U-Factor
The U-Factor is a measure of how quickly heat flows through a window. In short, the lower the U-Factor, the better your window is insulated. It’s important to keep in mind that the U-Factor reflects not only how quickly heat from inside your home will flow out into a cold environment, but also how quickly the sun’s heat will heat up your home in the summer. The U-Factor measures the insulation of not only the glass in your new windows, but also the insulation benefits of the frames and any coatings on the glass (we’ll talk more about this later). Here in Cincinnati, because we’re pretty far north on the planet, a U-Factor of less than .3 is ideal. When it comes to selecting windows with a low (and thus better) U-Factor, you can also get “more bang for your buck” by purchasing low U-Factor windows for your northern and southern facing windows, and saving a little by not worrying as much about the U-Factor on your east and west facing windows.
SHGC
The SHGC (or Solar Heat Gain Coefficient) of your windows measures the amount of solar heat that can pass through your window. (Just to clarify — U-Factor was the rate, SHGC is the amount.) Unlike U-Factor, where a lower number is always better, the ideal SHGC for your home is going to depend on the climate where you live. A lower SHGC is better if your main concern is keeping your home cool in the summer, while a higher SHGC is better if your main concern is keeping your home warm in the winter. If you live in Arizona or Maine, this will probably be an easy choice, but if you live in most of the rest of the US, you’re going to need to think about the heating and cooling needs of your home, and probably discuss the options with a window replacement company based in your local area. The SHGC of your new windows will be determined by the type of glass in the window, whether or not there are any coatings on the window, and its position and orientation in your home. If your main concern is keeping your home warm in the winter, and reducing your heating bills, you will want to put high SHGC rated windows on the south facing side of your home. If your main concern is keeping your home cool in the summer (or year-round) and reducing the cost of your air conditioning bills, you will want to put low SHGC windows on the south, east, and west facing sides of your home.
Low-E Coating
Low-E Coating is a thin metallic film that is applied to the surface of a window to increase the amount of solar heat and UV light that are reflected off of the window’s surface, while still allowing light to enter. Low-E Coatings can increase the U-Factor and the SHGC of your windows, for improved energy efficiency and reduced heating and cooling bills.
There’s a lot to understand about replacement windows, especially when you’re concerned about energy efficiency. It’s a good idea to talk with an expert, especially a window replacement company in your local area that has experience with the specific climate concerns where you live. If you’re lucky enough to live in the Cincinnati area, you can call us here at Harper Siding and Roofing, and we can show you how to optimize your choice of new windows for energy efficiency and improved heating and cooling here in the Cincinnati area.