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BECOMES THE PROBLEM

QUESTIONABLE SOLUTION - When looking at the NFRC label, it’s important to remember that a window’s overall thermal
performance is the result of all its contributing factors, and that frequently an adjustment to one area can have undesirable
effects in another. For example, it’s easy to reduce the unit’s U-Factor by applying additional layers of Low-e glass. However,
this would also have the undesirable effect of reducing both VT and SHGC, so it’s important to maintain a balance in all areas.

One particular measurement of importance to people in the cold
Northern climate zones is the unit’s Condensation Resistance Factor
(CRF), since the accumulation of excessive condensation can be
particularly detrimental not only to the building’s structure, but to
the indoor air quality as well. Since this number (which ranges from
1 - 100) is not required to be reported, most architects, building
professionals and homeowners are unaware of its existence, much less
its importance.

Unfortunately, in order to meet Energy Star 6.0, some manufacturers
®
have chosen to resort to so-called "Surface 4" or "roomside" Low-e
glazing. Under this technique, an additional layer of low-E coating
is placed on Surface 4 (S4) of the glass of a traditional improved IG
(generally, low-E and argon fill).

According to industry experts, the science behind S4 results in a
higher risk of condensation in cold weather because the Low-e coating
reduces radiant heat transfer from the room to the glass surface. While
this does improve the window U-factor by about 0.03, ultimately the
room-side glass is cooler, which increases the chance of an excess
of water vapor condensing on the glass surface, which can result in
sheetrock damage, peeling paint or mold growth.

This is the unintended, yet potentially dangerous consequence of S4
glazing: a dramatic reduction in the CRF, with a resulting increase in
condensation on interior glass surfaces, and the subsequent damage
that results.

PROTECT YOUR HOME, PROTECT YOUR FAMILY - How can you be sure the window you are specifying or installing has the
recommended CRF for your climate zone? What is the recommended CRF for your climate zone?

According to both the American Architectural Manufacturers Association (AAMA) and NFRC, for the cold Northern climate
zone, windows should have a CRF of at least 50. This will provide a sufficiently warm roomside glass surface to resist moisture.
Even with a CRF above 50, windows in highly humid areas of the home (kitchens and bathrooms) may show some occasional
condensation, as may other windows in the home during the seasonal transition from Summer to Autumn. This type of
condensation should not be a cause for alarm. What should be a cause for alarm would be continuous, daily, uncontrollable
condensation.

But how can you find the CRF it’s not on the NRFC label? First: ask the
manufacturer, as they are able to provide this information to you. Or you can
find our for yourself by visiting www.NFRC.org, hover over "Consumers" in the
top menu bar, then click on "Search for a Fenestration Product". This will pull
up a search tool, with which you can search by manufacturer, window type, as
well as by minimum U-Factors, SCGC and VT. Included in all reports is the Condensation Resistance
unit's CRF.

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Better yet: ask them if they use S4 glazing in order to meet Energy Star 6.0. If If it’s important enough to measure,
they are, then chances are the CRF for that unit may not be the best choice to it’s important enough to report.
protect your home, and protect your family.
We’ve all seen it: interior window condensation forming on cold days. Under Energy Star
®
6.0 performance standards, many window manufacturers are making choices that will
actually increase interior condensation to levels that may prove to be costly to homeowners.
For this reason, Mathews Brothers advocates the display of the CRF on the NFRC Window Label.

BECOMES THE PROBLEM www.mathewsbrothers.com