When it comes to choosing windows for your Dearborn home, it’s probably clear that energy efficiency is going to figure into you decision. After all, who doesn’t want reduced utility bills and increased comfort all year long?

What may not be quite so clear is whether the windows you’re considering are truly energy efficient. How can you really know if you’re buying an energy-efficient window—and how can you compare the performance of different windows?

One way to ensure that you’re getting what you really want is to check out a window’s certification with programs such as the National Fenestration Rating Council (NFRC) or to look at a window’s ENERGY STAR rating. Both of these organizations rate a window’s performance on factors such as U-Factor; Solar Heat Gain; Visible Transmittance; and Air Leakage. Here’s a quick look at what those criteria really mean.

  • U-Factor: Your window’s U-factor measures how well the window keeps heat inside your home by measuring the total heat flow through a window or door from room air to outside air. The lower the number the better a window’s insulating capability is. That’s particularly important in climates such as we have in Michigan with cold winters and hot summers.
  • Solar Heat Gain Coefficient (SHGC): Your window’s SHGC measures how much radiant heat enters your home. Again, the lower the number, the less heat your window is letting in. Of course allowing some solar heat in (particularly in cold Michigan winters) can be a good thing. So you’re not looking for a reading of zero. And bear in mind that this is just one measurement you’ll want to balance with the others.
  • Visible Transmittance (VT): The VT of your window refers to the amount of visible light transferred through the window. Low E glass coatings can keep out solar heat gain without reducing the visible light that passes through the glass. If you want to maximize natural daylight, you want a higher VT.
  • Air Leakage: This one is pretty obvious in that it refers to the amount of air that passes between the inside and the outside of your home through cracks in a window assembly. The lower this number is the better the window is doing at preventing heated or cooled air from escaping.

Here is one other thing to consider when purchasing new windows for your home. For a short time (through December 31, 2016) you can still take advantage of tax credits for energy-efficient windows. To qualify, your windows must meet ENERGY STAR requirements and be installed at the taxpayer’s primary residence. The tax credit equals 10% of product cost, excluding installation costs, up to $200 for windows and up to $500 for doors. Homeowners are limited to $500 total energy efficient tax credits, including claims from previous years. See www.energystar.gov/taxcredits for details.