Volume 42, Issue 4 - April 2007
|All Together Now:
IGMA Continues to Harmonize Standards, Clarify Guidelines at 7th Annual Meeting
By Megan Headley
Seeing clearly was a cause of concern for members of the Insulating Glass Manufacturers Alliance (IGMA) in February. During its annual meeting, held February 21-24 in Tampa, Fla., IGMA’s visual quality working group worked to clear up its guidelines on visual obstructions in insulating glass units (IGUs). Visual quality working group members were concerned that dirt, debris and fingerprints can’t be absolutely eliminated in IGUs and the guideline’s requirement that certain obstructions should not be allowed was excessive. Other members were concerned that visual obstructions addressed by the IGMA guideline might already be addressed in other industry documents, notably, ASTM C1036 Standard Specification for Flat Glass.
Visual obstructions were but one issue addressed at IGMA’s seventh annual meeting. Committee members met on a number of topics during their four days in sunny Florida, addressing guidelines on capillary tubes and gas fill content, among other issues. In addition, attendees were treated to technical presentations on topics including the impact of glass products on vinyl siding distortion, the impact of a glazing system’s solar heat gain characteristics on the energy consumption of a house and what IGUs go through during a hurricane.
I Can See Clearly Now the Dirt and Debris Are Gone
Following discussion on what constitutes a visual obstruction, the group agreed that many of the items listed in section four should, in fact, be quantified. The group agreed only two items, fogging and suction/vacuum cup marks, should continue to be listed as “not allowed” in the document.
Several group members commented that the type and quality of the lighting could also impact the visibility of an obstruction.
Chris Barry of Pilkington suggested the document state that standard lighting conditions be used to determine the visibility of an obstruction.
Bruce Virnelson of PRC Desoto International reminded the group that fog is sensitive to lighting. “There has got to be some sort of comment in there on lighting,” said Virnelson.
However, others note that lighting conditions can’t necessarily be controlled in the field.
“If you’re getting very prescriptive with the lighting, how are you going to meet that in the field?” asked Tracy Rogers of Edgetech.
With these new questions in mind, the working group will take another look at this section before the summer meeting.
The glazing guidelines working group members worked on providing guidelines for how to close capillary tubes in the field.
“My charge was to evaluate some of the methods that are used,” said Bill Lingnell of Lingnell Consulting Services.
Lingnell had begun by examining two methods for closing capillary tubes. He said that crimping the tube, or pushing it down with pliers at intermediate points, seemed to be inconsistent and found that using wire snips to cut off the end sealed the tubes nine out of ten times. He requested that members send in information on the methods they use to seal capillary tubes in the field.
Virnelson noted that it could be useful to observe not only successful techniques for closing capillary tubes but also watching how successful those techniques remain over time.
“What it decays down to may be a good indicator,” he said.
During the technical committee’s meeting, members questioned whether, in addition to current guidelines on how to use capillary tubes, there should also be guidelines for when to use them. Several committee members agreed that there are manufacturer-specific recommendations available, but that an industry-specific consensus could be helpful.
Getting Their Fill of Gas Content Concerns
“It’s certainly a major step toward putting these two programs together,” said Margaret Webb, IGMA executive director.
There was also a motion to make gas content certification voluntary rather than mandatory. Several committee members said that making gas content certification mandatory adds substantive cost for manufacturers with few gas-fill products who still want to certify the durability of their products. The group accepted the change to voluntary certification, with the caveat that they hope to require mandatory gas content certification again in the future.
“There was real resistance to carrying two types of spacer, labeled and unlabeled,” said Webb. “[IG manufacturers] may choose to participate in just one program.”
The committee members had also addressed the question of whether testing double-glazed units would qualify in lieu of testing triple-glazed units. Committee members approved the schedule following IGCC for testing triple-glazed units every four years. Double-glazed units would be tested in interim years.
Cardinal Addresses Distortion of Vinyl Siding
“Glass does reflect and it does shine on other buildings and if those buildings are of susceptible materials there could be problems,” Haberer said.
Vinyl is particularly susceptible to bending and cracking from heat.
“Other siding products are not as vulnerable as vinyl,” Haberer said. “It’s due to the relatively low distortion temperature of vinyl.”
The distortion of vinyl begins to occur at temperatures of 160º-165º Fahrenheit. Dark colors of siding can have up to 80 percent absorption of the sun’s rays and Haberer noted that some building construction can increase the amount of heat hitting the building. He showed images of inside corners with windows, where the rays hit the siding directly at the same time that rays deflected from the window hit the perpendicular wall as well, further raising the temperature of the vinyl.
The study examined the impact of reflective coatings on this type of damage.
“The more reflective coatings that are out there today, that are getting more popular, are going to create this problem,” he said.
While reflective glass did create problems, researchers found that even clear glass can become a significant heat source.
“The study indicates that even clear glass can raise siding above distortion temperature,” Haberer said.
He recommended following the advice of the Vinyl Siding Institute (VSI) at this point, since no solution is currently available from the glass industry. VSI recommends installing a screen in the problem-causing window or installing an awning over the window to break the line of light reflection. The institute also suggests the use of shrubbery to protect the impacted area of siding from reflections or radiation.
Testing for Energy Consumption
For Barry’s test, benchmarking of the two houses was performed by using a high solar transmission low-E coating on surface 3 of all of the double-glazed argon-filled windows and patio doors in both houses. Twenty-three windows and both the fixed and sliding portions of a patio door were included. Next, the IGUs in the test house were replaced by insulating glazing systems with a low solar transmission low-E coating on surface 2 of the double-glazed argon-filled windows.
The house was tested for four weeks during the winter, January 19-February 15, 2006, when the average temperature measured 24.4º Fahrenheit. Natural gas and electricity consumption and air and window surface temperature measurements were recorded. Preliminary results showed that the use of low solar transmission glazing systems increased the gas consumption in the test house by about 8.7 percent relative to its performance with the high solar transmission glazing. The electric consumption was increased by about 1.3 percent as a result of the reduced solar heat gain.
Barry said the initial results suggest energy savings using high SHGC and low-E glazing, from New York to Seattle and further north. He added that detailed results of the study, including the results of monitoring the windows during the hot and humid summer months, will be presented at a future IGMA meeting.
The Effects of Hurricanes on IGU Performance
First Lingnell explained what happens in a hurricane event, giving examples of historic hurricanes and outlining the science of how hurricanes are created. He explained that the lower the atmospheric pressure, the worse the storm. That led into a discussion on preparing IGUs for being under pressure in a hurricane.
“The pressures that occur during the hurricanes are low pressure and they are usually substantially lower than the pressure that exists in the sealed IGU,” said Lingnell. “The changes in barometric pressure will cause stress on the edge seals and stresses in the glass.”
Lingnell noted that glass is elastic and is going to move under pressure, and that movement should be accounted for in both the glass and the surrounding components.
“Hurricane speeds can relate to a substantial pressure on the glass and as such the supporting members should be reviewed closely to find out how much deflection will be predicted during the loading conditions,” he said.
In particular, he explained that high deflection can cause shear stress on the bond of the IG sealants. He said it needs to be verified that the stress on the edge seal is not in a zone that is detrimental to the sealant.
Another problem resulting from hurricanes that can be overlooked is the intrusion of water. Part of the problem, Lingnell said, is that when water is driven into the unit by hurricane-force winds, it can’t necessarily find a way out.
“The glazing condition must be designed so that water and moisture have a way of exiting so as not to be detrimental to the sealants,” said Lingnell.
Lingnell noted that water trapped in IGUs can be a major culprit of seal failures.
“Look for let-go or bond-loss conditions that lead to seal failures and loss of seal integrity due to water entrapment in the glazing system,” said Lingnell. “This one’s kind of important.”
Finally, Lingnell addressed a common question he hears asked of IGMA: “Does a hurricane cause a seal failure?”
He said that it depends on the unit and should be observed on a case-by-case basis, as a number of factors could contribute to seal failure, some of which are the result of a hurricane.
For more information and updates on these topics, make plans to attend the next IGMA meeting, June 11-13, 2007, at the Hyatt Regency Huntington Beach Resort and Spa in Huntington Beach, Calif.
the author: Megan Headley is an assistant editor for USGlass.