Glass Manufacturers Have Different Opinions on ENERGY STAR Draft Requirements

The debate over whether one type of glass is right for all regions of the country has been going on for some time. Current ENERGY STAR requirements specify that a window must have a certain U-value depending upon the climate zone, but allow for any solar heat gain coefficient (SHGC). However, last week the U.S. Department of Energy (DOE) released its Energy Star for Windows, Doors and Skylights Revised Draft Criteria and Report, which now specifies a SHGC for different regions. Based upon the draft revisions, for example, the same windows sold in the South-Central region will not be allowed in the North-Central region.

The ENERGY STAR draft requirements have a seen a mixed response from glass manufacturers.

Paul Bush, manager of technical services for PPG, sees the changes as a positive step.

"ENERGY STAR has always been a positive for the industry and PPG has been involved from the beginning. We continue to support the details of the revision and we think the use of multi-climate zones has merit," says Bush "The more zones there are provides the ability to maximize high-performance glazing products by region, particularly in the Northern climate zones.

He continues, "[Studies] have shown the cost benefit of passive solar in northern regions. [Prior to these draft requirements] there was a one-size-fits-all approach, but now that's limited because of the alternate compliance path. This way you'll have the best product for the best region."

Some companies, however, may not view the draft as favorably. Cardinal Corp., for example, supplies many residential window manufacturers with high-performance low-E glass that has been used in areas all over the country. In the July/August issue of DWM magazine, Jim Larsen, the company's director, technology marketing, said he's certainly not against the requirement of solar gain in the north and agrees that it can be beneficial. The issue, he says, is knowing the trade-off.

"The trade-off is that you really need an active homeowner to get the true benefit of the passive solar gain without the discomfort penalty," said Larsen. "You have to practice opening and closing the windows during the swing season, opening and closing your blinds and certainly looking at having some building attributes that are more advantageous toward using passive solar gain."

He added, "You must always go for comfort first. One of the premises and the reason why high SHGC didn't stay a fixture in the northern marketplace is because a typical house ended up sacrificing on comfort."