Are Triple-Pane Windows a Good Investment?

As efficient building envelopes become more of a priority for builders, you may be considering investing in triple-pane windows for the R-value they offer. The technology behind window design has improved in leaps and bounds Are Triple-Paned Windows a Good Investment 2as manufacturers attempt to overcome the poor insulation value that windows traditionally offer the home builder. Unfortunately, the improved insulation comes at a high price. Do triple-pane windows offer sufficient energy-saving to justify the investment?

This is a difficult question to answer as not all windows are created equal. If you compare a high-performance triple-pane window with a mediocre double-pane, you could get an interior surface temperature difference of up to 10°F, but with higher performing double pane windows, this difference would be much lower.

If you just crunch the numbers, it may be difficult to justify the expenditure of thousands of dollars or (on average) about 30% more for triple-pane with your energy savings. You will have a ROI that may make you think twice, but the payback has a number of complexities to consider.

Future energy price increases may make your ROI more attractive. In the event of a power outage, a home with triple-pane windows won’t cool as quickly. But it seems the most important advantage that triple-pane windows offer is comfort.

In a study by One Sky Homes and the U.S. Department of Energy’s Building America program, researchers tested homes fitted with double and triple-pane windows to measure energy savings and occupancy comfort. What they found was that while the energy savings were not all that significant, the comfort factor was significantly different.

Allen Gilliland comments on their findings: “Obviously there’s a difference in energy performance as the double-pane window is losing heat and has a lower surface temperature inside during winter conditions versus the triple-pane which is allowing less heat to escape and maintaining a higher interior glass temperature. So the energy is important, but the real essence of this is occupant comfort.”

He goes on to explain that the real value of the triple-pane windows is that there is a lower temperature differential between the wall and the interior surface temperature of the glass. Triple-pane windows reduce the cold spots in the home which create convection currents, drafts and discomfort. “With triple-pane windows we eliminate cold surfaces, create a very small temperature differential between the wall and the glass, and we therefore have no convection currents and very even temperatures throughout the room and a very, very high level of occupant comfort,” said Gilliland.

Martin Holladay from the Green Building Advisor agrees: “Triple-glazed windows provide comfort advantages that can’t be quantified. When it’s below zero outdoors, you can sit in a chair beside a triple-glazed window and not feel cold. That’s worth something.”

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