Plavecsky's Ponderings By Jim Plavecsky
by Jim Plavecsky
August 27th, 2015

The Triple Advantage of Triple-Pane Window Design

As I travel visiting window fabricators, I’m seeing an increasing interest in the marketing of triple-pane window designs. These are the three reasons that I see triple-pane windows growing in popularity in the coming years:

  1. U-Value Optimization

Larger air gaps lead to increases in convection. Air has more space to circulate; as it does so, it transfers heat. So triple-pane designs use two smaller air gaps as opposed to a single larger air gap. Also, low-conductivity gases such as Krypton achieve their maximum advantage in smaller, more confined air spaces, so triple-pane designs maximize the benefit of exotic gases such as Krypton. Therefore, U-values can be optimized as two panes of low-E glass are combined with two cavities filled with argon or krypton. This maximizes the energy savings for the homeowner.

  1. Condensation Resistance

Back in the day, when I was first promoting the advantages of warm-edge technology, I would use a thermal camera at trade shows to show the advantages of warm-edge spacers. I worked at a company that also sold roofing repair systems. The roofing division had a thermal camera it would use to see where roofing systems were losing heat. So, I borrowed one of these cameras for a trade show to demonstrate how heat was being transferred across various window systems. I would place a heat lamp on one side of the window and the thermal camera would view the heat loss from the opposite side with the corresponding image displayed on a color monitor. Heat loss would show up as a reddish color pattern at the edge of the window.

Double-pane window designs utilizing warm-edge spacers would show a smaller degree of heat loss occurring at the edge vs. the same type of windows made with metal spacers. It was quite demonstrative. It’s true that a picture is worth a thousand words, because this demo really helped sell the advantages of the technology.

The next step was to show the triple-pane IG in compared with the dual pane design. When the thermal camera scanned triple-pane windows also built with warm-edge spacers, the color patterns at the edge nearly disappeared entirely. This indicated a minimal disparity between “edge of glass” vs. “center of glass” temperatures. Condensation would therefore be a non-factor in these window designs. This is a major advantage of the triple-pane window design. When it gets really cold outside, humidity in the home must get very high before condensation starts showing up on the edge of glass on the inside pane. No moisture, no damp mess, no mold—just a clean-looking window with maximum viewing area of fantastic scenery.

  1. Sound Attenuation

Triple-pane windows also allow window manufacturers to achieve higher STC ratings by taking advantage of the science of “decoupling.”

Materials of identical characteristics respond to sound waves in similar ways, amplifying the noise. So, by combining materials of dissimilar characteristics, sound waves of dissimilar wavelengths are generated which will tend to “decouple,” or cancel each other out. So, two different-sized air cavities vs. the same-size gaps, two different thicknesses of glass, and even two different glass materials such as conventional vs. laminated glass allow the triple-pane design platform to decouple sound waves, achieving higher STC values and sound deadening. The result is less sound, period.

Just as thermal performance has helped shape window developments over the last 20 years, sound attenuation will become increasingly important and thereby will help shape window design over the next 20 years. After all, homeowners want to enjoy their views, but they also highly value peace and quiet.

Sure, you can utilize a fourth-surface low-e coating and achieve some very low U-values as well, but with the additional comforts of condensation resistance and sound attenuation, a triple-pane design gets more appealing.

Therefore, as you consider the idea of offering a window design in the “Most Efficient” category, consider the triple advantage of the triple-pane window design.

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  1. Jim – very nice article breaking it down – triple vs. #4 low-e – good stuff.

  2. Triple glazing has a lot to recommend as Mr Plavecsky indicates. However, there are also some engineering and production issues that need to be considered.
    1) In moving to triple from double you are adding another 30% to the complexity of IG production. Make sure your materials, fabrication equipment and processeses, are up to the task.
    2) Triple IG is 30% heavier than double hence the need to confirm locking hardware, balances, rollers, profiles, and reinforcement if need are up to the task.
    3) Make sure your window design is compatible with the additional load of triple glaze; engineering calculations if not actual structural testing may be advisable.

  3. Hi Jim: Condensation is a tricky one and not sure it can be labeled as a non issue with triple pane glass. The improved performance of triple pane glass reduces the exterior glass surface temperature to the point that condensation will occur on the exterior pane. That indicates the glass is doing it’s job by reflecting heat back into the home. Since Autumn is just around the bend be prepared to address homeowner complaints about exterior condensation on their new triple pane windows. Some homeowners have a hard time understanding it is a testimony to the units excellent thermal performance.

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