July 12th, 2012
Pushing The Envelope on Thermal Performance Gains: There Are No Shortcuts
I read with great interest the DWM article covering the details of the debate on the subject of Surface No 4 Low-E Windows (insert link). Yes, using low-E Glass on Surface Number 4 can enable manufacturers to move the bar once again on U-Values of dual pane units. Some folks favor the use of this construction arguing that it achieves further U-Value gains without the added expense of triple pane construction and the window modifications that come along with the usage of triples. Others, however, favor the usage of triples, arguing that condensation resistance suffers when one uses low-E coatings on surface Number 4.
It reminds me of the time early on in my career when I was a polymer engineer working for a major tire manufacturer. I once came up with a new tread formula that seemed to take tire wear ratings to the next level. We built experimental tires and the results came back from the test lab with tires lasting 100,000 miles, about 25,000 miles greater than any existing tire product we had at the time.
I was elated. My boss, however, stared at me just smiling. “What are you smiling at Eldon?” I asked. “Well, Plavecsky, I have been in this business a long time and I have found that there are no shortcuts. Before we get too excited, let’s see how the tire traction tests turn out tomorrow.”
The next day, the tire traction tests were delivered to my desk and I learned the meaning of that phrase … “there are no shortcuts!” The tire traction tests were very good on dry pavement but less than stellar on snow and ice. We debated that perhaps we could sell this new tire as a fair weather tire with a superior mileage rating and continue to sell our specialized winter tires for best traction on snow and ice. However, in marched the market research guys!
Recent market research revealed that consumers no longer wanted to be changing tires every fall in time for winter weather to arrive. They simply wanted one tire that they could ride on all year long that would provide them with the best wear possible yet exhibit very good traction on all types of road conditions from January through December. And so the concept of the All Season tire was born!
The same thing goes with window U-value performance. Homeowners want an all season window! They want the very best thermal performance possible but they do not want to have to worry about condensation during the cold winter months when their house is buttoned up tight and humidity levels are higher in the home. Condensation is unsightly. It leads to mold formation on window surfaces and wood deterioration. Condensation just doesn’t jive with the whole concept of a high-performance window!
Triple-pane windows, however, offer both superior thermal performance and condensation resistance. With some additional modifications, significant gains in sound attenuation are also possible with a triple-pane design. Sure, window modifications are necessary but some extrusion suppliers have new designs that can accommodate either dual-pane or triple-pane glass packages giving the window manufacturer increased flexibility on a common platform.
So, in view of the fact that both legislative and competitive factors are indeed driving U-Values lower and lower, manufacturers must and will continue to push the envelope in terms of additional thermal performance gains. But as this engineer learned early on in his career … there are no shortcuts!