The North Carolina Building Code Council recently enacted an emergency rule in the state’s residential building code that allows builders to use non-low-E glass in areas where it poses a “safety concern.”

In the “Emergency Rule-Making Findings of Need” document submitted by the N.C. Building Code Council, “four documented cases of fires being caused by similar reflective energy involving Four Seasons and Cardinal IG Co.” are cited The companies, however, contend that the incidents were isolated, resolved and limited only to skylights and sunroom roof products that were discontinued more than a dozen years ago.

“The [Consumer Products Safety Commission] (CPSC) action referenced by the Council involves a specific roof glazing product that was introduced in 1996 and discontinued in 2002,” says Four Seasons Sunrooms senior vice president Brian Fabian. “The glazing was a high reflectivity product (Code 77) specified for its solar control properties. The potential fire risk associated with this product only existed when certain specific conditions were met.

“As part of the joint voluntary recall with the [CPSC], an agreed identification, inspection and repair program was implemented. Any installation found to match those specific conditions was addressed on site and the product repaired. There have been no issues reported from any of the repaired installations.”

Fabian adds that the specific Code 77 roof glazing product was limited to roof glazing applications, and that “subsequent roof glazing products do not utilize high reflectivity to achieve solar control performance but continue to utilize low-E coatings. There have been no reported issues involving the subsequent roof glazing products utilized by Four Seasons Sunrooms.”

Cardinal director of technology marketing Jim Larsen says the Code 77 glass has 66 percent solar reflectance, which is “nearly twice the reflectivity of typical double silver low-E glass used for vertical window energy code compliance in North Carolina.”

“Only Code 77 IG units that were outside of our tolerances for deflected air space gaps were involved (in the incidents). The curvature from this excessive deflection created a focal point on adjacent cedar siding which then created a potential risk of fire in four sunrooms out of approximately 6,000 installations.

“Installations from the applicable manufacturing time period were inspected and, if found outside of specification, were repaired onsite,” adds Larsen. “Correction of the air gap deflection/glass curvature when outside permissible tolerances has proven successful in mitigating the focal point concerns, with no known reports of subsequent heating issues in repaired units.”

The building council says citizens of North Carolina and other states “have been plagued” by incidents in which highly concentrated sun reflectance from low-E windows has caused damage to vinyl sidings of homes and plastic parts of vehicles.

Representatives of the glass industry, however, have pushed back over the past month, arguing that the sometimes high concentration of sunlight on low-E windows that has resulted in these kinds of issues has more to do with building design and site characteristics than the glass itself.

“We believe the benefits and efficiencies gained by the specification and use of low-E should not be abandoned due to isolated incidents of damage to vinyl siding and plastic auto parts,” says Fabian. “The use of high-quality, low-E insulating glass units made to exact specifications virtually eliminates the potential for these types of incidents while providing great value to the consumer and the environment.”

Adds Larsen, “While there have been reports of vinyl siding damage from sunlight reflectance off windows, to our knowledge these have been isolated in occurrence. No documentation of window‐related reflected heat has been presented to justify fire risk as the reasoning for the low‐E exemption. We stand ready to lend our expertise to North Carolina in forensic evaluations, if needed.

“In our opinion, the low‐E exemption puts home affordability at risk. Furnaces will need to be about 10 percent bigger to accommodate larger heating loads and air‐conditioners will need to be upsized on the order of 35 percent to accommodate solar gains from clear glass. Annual heating and cooling costs will be about 15 percent higher.

“Based on what we learned from the skylight event, Cardinal IG upgraded its manufacturing operations and process control capability. Over the last couple of seasons, our IG customers haven’t reported to us any issues on vinyl siding degradation. We believe that our enhanced quality efforts and deflection control are the reason low‐E remains a viable and proven technology for improved window energy performance.”

According to Jeff Inks, vice president of code and regulatory affairs at the Window and Door Manufacturers Association, public comments to the council regarding the rule are due August 8, and a hearing will be held September 9. Inks contends North Carolina’s acts “aren’t warranted” and could have a “significant impact on energy efficiency.”

“It wouldn’t be a step back,” he says. “It would be a leap back.”

According to AAMA’s recently released U.S. Industry Market Studies, 81 percent of conventional residential windows in the U.S. utilize low-E glass.

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