Tuesday, March 1, 2011

Guest Blogger, Dowd, Discusses Common Misconceptions about Window Technology

Dean Dowd is the Chief Technology Officer for NFRC member company, CalFinder. This week, Dowd picks up where he left off, providing additional thoughts on understanding energy efficient windows.

By Dean Dowd

There are many misconceptions, not to mention all-out, baseless myths—about replacement windows and their performance. So, without further adieu, let's get to debunking and shed some light on the matter.

Four Common Window and Window Replacement Myths

1. Installing highly energy efficient windows will save you hundreds of dollars per month or year.

Some claims regarding the amount of money one can save are exaggerated. Say, for instance, that you buy and install a brand-new window with the highest energy-efficiency ratings (U-Factor of about 0.18 and an AL of <0.3 cfm/sq ft, for example) for an average cost of $130 plus installation. While the resale value of your home definitely goes up and you'll likely experience less heat gain in the summer and more in the winter, your return on investment (ROI) will be very minimal for several months, and it will take at least a year or two to recoup the cost of the window and installation.

It is best to think of your investment in windows as producing a return over time rather than right away.

2. Replacing an older single-pane window with a double-pane, double-glazed one will always raise energy efficiency and lower heating and cooling bills

The lines are a little blurry on this idea. In a perfect scenario, yes, double-pane glass will be significantly more energy efficient than older, single-paned ones, especially if the latter is poorly sealed. However, even double (or triple) pane windows can be just as energy-robbing as old windows if the sashes and frame are incorrectly installed, and/or the window edging is improperly fit to the structural frame (even if it's only off by a centimeter).

3. In the event of a tornado, opening a window or two will help balance the pressure inside the house when the ultra-low pressures inside a tornado hit, thus preventing the explosion (or implosion) of the house.

The physics of this one are actually pretty sound in theory, but with one major problem: in the real world, a tornado's raging, 100-mph-outer-winds will annihilate virtually anything in their path, so you'd be very fortunate to reach that point in a tornado (to that theoretical point of ultra-low pressure near the center) without your entire house being ripped off its foundation first. Therefore, it's completely nonsense.

4. Simply placing newspaper, a towel, or other 'insulating' material between the frames will solve the problem of old, drafty windows.

This "theory" is probably the easiest one here to quickly dispel. Using household items such as duct tape, towels, newspaper, or—the worst idea ever but one that's too frequently seen—aluminum or tin foil, may provide very short-term relief from heat gain or loss, but is ultimately just a band-aid that will eventually have to be replaced with a professionally-made and engineered window, as even half-good window manufacturers sell.

We hope this has helped clear up some of the most often-repeated myths about window technology. If you have any more questions or myths to debunk, just let us know in the comments below.


  1. How does the window of a car close automatically? Or what is the technology behind it?

  2. NFRC operates a certification and labeling program for residential and commercial windows. We are not involved with automotive windows. I wish I could be of more help.