Perhaps one of the easiest ways to tell if a window option you’re considering will perform as you’d expect is to look for the energy star windows logo. The department of energy puts together the guidelines for energy efficient windows and they provide a pretty solid benchmark for performance.
As you might expect the someone in Maine doesn’t need the same windows as someone in Arizona. The department of energy divides the country up into climate zones, each with their own requirements.
For 2014 the requirements energy star windows requirements are the same as they’ve been for a little while and every manufacturer will have qualifying double pane options. You can see the requirements for your climate zone in this chart:
Basically, the differences in requirements across the country come down to the idea that in the colder areas you want the heat from the sun to help warm your home in the winter and in the warmer climates you’re more concerned about keeping the solar heat out in the summer.
As you can see in the chart, in the north and north-central regions a solar heat gain coefficient (or SHGC) as high as 0.40 will qualify, but in the south the max qualifying SHGC is 0.27.
The differences in required u-factors are a little less intuitive. Basically this comes down to the fact that in the very warm southern climate zone the u-factor is almost irrelevant. If the window keeps the suns heat out it qualifies as energy star windows. As you can see a u-factor as high as 0.60 can still qualify in these areas. That’s not a particularly efficient window, but if it reflects enough of the suns heat to get to a SHGC of 0.27 then it does the trick.
In climate zones that experience both hot summers and cold winters the requirements are a little more balanced.
The long and short of it is that if you want a quick way to tell if a product is pretty good this is a great place to start. There absolutely are more efficient options out there, and you certainly may want to consider them, but the bang for your buck starts to diminish as you get more efficient.
Are there tax credits for new windows?
Currently there is no federal tax credit available for energy star windows, but our friends in congress may well pass a retroactive tax credit (it’s been done before). If they do you’ll probably only qualify if you purchased energy star windows.
One could write an entire post on the wisdom (or lack thereof) in implementing a tax credit designed to incentivize a specific behavior (purchasing efficient windows) and then making it apply to people who have already made the desired decision without the need for the incentive. Perhaps we’ll leave politics out of this party and save that conversation for another day
Are the 2015 energy star windows requirements any different?
One last factor to consider is that the 2015 energy star windows requirements have now been released and they’re getting more stringent. It might be worthwhile to look into models that meet this standard today. You can find more info on requirements for 2015 energy star windows here.
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