Window Glazing and Energy Efficiency

From on April 03, 2008 in Energy Efficiency

Window GlazingIn a utopian world, we would turn on our heaters once a year at the onset of winter, warm up our homes, and put the heater to rest for the remainder of the year. If only our homes could be perfectly energy efficient. Alas, we’re not there yet, but we are making definitive strides! In just about every aspect of home building and design, improvements in energy efficiency have taken top priority. Windows are certainly no exception. Traditionally, two of the weakest points in a house’s insulation value have been its windows and doors.

Thankfully, window glazing technology has made leaps and bounds toward energy efficiency. If you are building anew or just remodeling your home, there are very important factors to consider when choosing your new windows and doors. Glazing, in terms of windows, occurs when the manufacturer hermetically seals two separate panes of glass together, leaving an air space between the two panes. This air space, coupled with the extra glass, makes the window more energy efficient by resisting heat flow.

Two important statistical features to consider when choosing a type of window glazing are its R-value and U-value. R-value measures the amount of heat lost through window glass. The higher a window’s R-value the better it prevents heat loss. A single-glazed window typically has an R-value of R-1, while a dual-glazed window’s value is R-2, effectively doubling the window’s efficiency. U-value factors time into the equation. It is a measurement of heat that escapes per hour. In this case, the lower the U-value the more efficient the window or door. Here is more information about the technical terms related to window efficiency.

There are several different types of window glazing, all of which will upgrade the energy efficiency of your home. One type of glazing I find fascinating is Low Emissivity (Low-E) coating. Low-E coating is a thin, virtually invisible coating applied to one of the glass surfaces or suspended between the two. This coating allows light to penetrate but blocks out radiant heat waves (and keeps them inside during cold winter months). Windows with a Low-E coating cost roughly 10%-15% more but can save up to 30%-50% more energy. Low-E coatings can also be applied to existing windows. While this application is slightly less energy efficient it is considerably more inexpensive than full window replacement; an excellent option for do-it-yourselfers!

Don’t hesitate to ask the window manufacturer/supplier or your window contractor about the energy ratings for any windows you may be looking to purchase. Glazing is the crux of energy efficiency in windows and will be a worthy investment over the life of your home. Take your time, ask questions, research if you need to. There are plenty of choices in windows and glazes so find what you like, at a price you can afford, and enjoy lower energy costs for years to come!