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Continuing our discussion on the energy-saving features we put into our house, today I’ll talk about the windows we used.

In the first two installments of this series, I discussed the framing techniques we used and reflective roof decking. Both of these features have added tremendous energy saving potential to our house. For a full list of the energy saving techniques we used, read the overview post.

Windows

For all the windows in our home, we installed a double-paned, low e, argon-filled window manufactured by Harry G. Barr Company of Ft. Smith, AR. The windows have a U factor of 0.31. If these terms don’t mean much to you, don’t worry. When I started researching windows it was all very confusing. I’ll discuss each of these terms below.

Single vs. Double Paned

I’ve lived in a house with single paned windows. The difference in insulation value of a single versus double paned windows is significant. In a previous home we remodeled, we upgraded from single-paned windows to plain double-paned windows. The difference was dramatic in the comfort level of the home. There were fewer cold/hot spots along the walls, and our heating/cooling costs improved dramatically.

Argon Filled

For our new home, we decided to go one step further. Our windows included Argon gas that filled the gap between the panes. Argon gas serves as an insulator, thereby improving the window’s ability to resist heat flow. Based on the research we did, the argon gas won’t last forever. It will eventually find it’s way out of the gap between the panes. I considered not using it, but the additional cost was just a few hundred dollars.

Low E Coating

LowE (or low emittance) coatings are used to suppress the heat flow passing through the window. Here’s a good description from Efficient Windows.org.

“Coating a glass surface with a low-emittance material and facing that coating into the gap between the glass layers blocks a significant amount of this radiant heat transfer, thus lowering the total heat flow through the window. Low-E coatings are transparent to visible light. Different types of Low-E coatings have been designed to allow for high solar gain, moderate solar gain, or low solar gain.”

The Low E coating was the single biggest thing we added to our windows that improved the energy efficiency.

U Factor

The U Factor is the measure of the rate of non-solar heat loss or gain through a window.  The lower the U Factor, the greater the resistance of the window to heat flow and the greater its insulating value.  My goal was to choose a window with a U Factor of 0.32 or less.  The windows I chose have a U Factor of 0.31 with the Argon gas.  When and if the Argon dissipates over time, the U Factor will still be 0.35.  Compare this with common U Factors of 0.50 and higher in normal new construction, and you can see why our windows are head and shoulders above others.

Bottom Line

Windows are a huge part of the equation in constructing an energy efficient home.  With windows 30 - 40% more efficient than normal windows used in new construction, the additional cost we incurred will pay for itself in just a few years.  We will see the benefits for many years to come.  If you are considering replacement windows for your existing home, the above advice still applies.  Make the investment in quality windows.  You’ll see the benefit in cost savings and in the comfort of your home.

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