Replacing Your Windows? Why U-Factor Matters

If you’re considering replacing your windows, you’ve probably run across the term, U-factor. This term helps to identify the energy-efficiency of windows, which in turn helps you understand how much they can help you save money on utilities. Understanding what U-factor represents to you will help you determine which replacement windows are the right choice for you, your climate, and your home.

The U-factor indicates the insulation value of windows; a window with a lower U-factor has greater heat resistance, which in turn means it has superior insulating properties. The rating that is widely used was introduced by the National Fenestration Rating Council (NFRC). The U-factor of a window can vary depending on several factors – particularly the framing and the type of glass used.

In some cases, you may also see references to the center-of-glass U-factor. This rating refers to the overall performance of the glazing only; it does not take into consideration the effects of the frame. For the majority of energy-efficient glass/windows, the U-factor for the entire window is greater than the center-of-glass U-factor.

Here in the United States, ENERGY STAR® has classified each region into a climate zone. Here in central North Carolina, we’re in what is classified as the North-Central climate zone; this means that we’re more concerned about summer’s heat than winter’s chill. Your ideal U-factor may vary. If you’re interested in seeing more information on determining the ideal U-factor for your area, visit here.

The replacement windows best suited for North Carolina’s hot summers and cool winters are those with U-factors of 0.30 or below. Renewal by Andersen of Central NC offers an excellent range of Low E4® replacement windows in Raleigh that feature U-factors that are ideally suited to our warmer climate. These windows benefit from both a framing material, Fibrex®, with good insulation properties as well as glass that effectively reflects away heat.

Does U-factor really matter? Keep this in mind: The average home spends between $1500 and $2500 on energy bills – and almost half of that cost is for heating and cooling. Poor-performing windows can account for a significant percentage of a home’s heat loss in winter and heat gain in the summer. So take the time to know the U-factor of your replacement windows – and remember that an investment in extra efficiency now can pay dividends for years to come.