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I am sure that the Energy Star program is not going to help me.

The USA Energy Star program helps people find energy efficient windows. It guides us to prefer windows with low U-Factor and low solar heat gain coefficient. This is good in two circumstances:

  1. In a climate with more cooling days than heating days, such as the southern climate zone.
  2. In a perfectly insulated house, in winter, that retains generated heat so well that heat from sunlight isn't welcome.

But in an old house with mediocre insulation, sunlight is welcome in winter. Windows with a higher heat gain coefficient allow the sunlight to warm the interior of the house. This can save energy, in a climate with more heating days than cooling days.

To mitigate the higher heat gain coefficient on a hot summer day, the sunlight can be blocked with a blind. This can be done very efficiently using a blind on the exterior of the window or embedded within the window (i.e. between two panes of a multi-pane window).

The USA Energy Star program steers people away from using windows in this way. As a result, homeowners in the northern climate zone, in older houses, are installing windows that help them in summer months. But many of these people might really benefit financially from windows that help them in the winter instead.

If you compare the USA Energy Star program to the Canada Energy Star program, you'll see a difference in priorities. As a result, certain windows (with higher heat gain coefficient) that are Energy Star certified in Quebec are not certified in Maine.

There are parts of the USA where heating costs are relatively higher, because passive cooling is relatively easy and effective. In these parts, costs can be reduced more effectively using windows with high heat gain coefficient.

Update: Please do not turn this into a political discussion.

I think the answer has to do with the subtlety of cost savings versus comfort, as benefits of windows' technical properties. It appears that the USA Energy Star program places full weight on cost savings, while in Canada the cold is so extreme that a balance between cost savings and comfort must be struck. I was hoping to find a window engineer on this forum who could explain authoritatively.

As an example of a window rating system that goes way beyond Energy Star's yes/no binary value, check the Energy Calculator provided by Canadian glass manufacturer Cardinal. It gives results of different glass products in terms of both savings and comfort. Comfort is further broken down into seasons. This level of information should be available to end consumers of framed windows, and should be incorporated into location-based government certifications.

Update 2: Efficient Windows Collaborative

I found a website, sponsored by major window manufacturers and suppliers, and originally founded by the Department of Energy, which helps consumers choose the right windows based on building location and design. It directs users to specific window types that are offered by various manufacturers.

This is much more useful than the Energy Star yes/no rating system. In addition to cost savings and comfort as attributes of window performance, it discusses condensation on window surface as well.

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    This question appears to be off topic, because it's about government policy not do-it-yourself home improvement. – Tester101 Apr 19 '15 at 14:49
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    Voting to close - this is politics, not home improvement. Reality of the market is that I actually looked at getting in high SHGC windows (which I was going to have to import from Canuckilvainia) and it was about 3X the price of the low SHGC windows - so I'll put up some high SHGC thermal collectors which I can just vent in the summer, rather than whinge about it on the internet much... – Ecnerwal Apr 19 '15 at 16:12
  • If it walks like a duck and quacks like a duck, it's not a platypus. It's politics, plain and simple - Canada has a mostly-heating climate, so high SHGC saves money in Canada. By that yardstick the programs are exactly the same - for an entire country. We have idiots that we keep electing into our government, so windows you can now buy in the US are only optimized for South Carolina, Southern California, et al. Couldn't be more political. It's virtually impossible to get a hard-coat low-E window in the US anymore (those are the insulates well, but has high SHGC type) – Ecnerwal Apr 19 '15 at 17:44
  • I'm having difficulty seeing how this question pertains to do-it-yourself home improvement, as it's not clear what exact problem you're having. Are you having trouble installing new windows, or trouble selecting windows appropriate for your project? Could you edit the question to make it more clear what problem you're having? As written, it sounds like you're simply complaining about the policies of a government run program. – Tester101 Apr 20 '15 at 11:20
  • As is, the reopen edit on this one doesn't go far enough to turn it into a question. It's still centered around discussing the shortcomings of the Energy Star ratings rather than actually ASKING a question. – Doresoom Apr 27 '15 at 13:56
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The true answer is that it takes more energy to remove heat from a space than it does to add heat to a space. For every watt of heat you want to remove, you have to expend an additional 2 to 3 watts of heat just to carry that first watt away from the area. So, insulation will always be biased towards preventing heat ingress.

  • Thats not what I was talking about. My answer comes from experience designing computer server rooms / datacenters. If you have a 1000 watt heat load (a machine) dumping heat into a room, you need to burn 2000 more watts to get rid of that first 1000 watts of heat. – cathode Apr 19 '15 at 17:43
  • Data centers are the nadir of thermal design - certainly nothing like a house. Some of the newer ones are bit smarter, and actually doing things like using outside air, but so long as you are adding gigantically inefficient transfer between the heat source and the heat removal you'll be far below the raw efficiency of a heat pump... – Ecnerwal Apr 19 '15 at 17:52
  • This answer assumes that ducted forced air cooling is the only solution. Many homes in the north can take advantage of passive cooling methods (or simply opening the windows), whose energy cost is zero. – Jacob Apr 19 '15 at 18:04
  • Actually its more like 1 watt to remove 20 watts of heat, so to remove 1000 watts you only need 50 watts of power. Ignoring the cost of moving air around. – Dan D. Apr 21 '15 at 16:57

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