Roller wave distortion spec requirements

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Author Message Chris Sawyer, AIA CCS LEED AP Senior Member Username: csawyer Post Number: 14 Registered: 02-2009 Posted on Tuesday, August 04, 2015 - 02:09 pm:    I’ve had some previous issues with roller wave distortion and was wondering if anyone had come up with spec language that might at least alleviate the worst case scenarios. My most recent attempts are specifications so that the tolerance for roller wave is a maximum of 0.003" (0.076mm) from peak to valley in the center of lites, and a maximum of 0.008" (0.20mm) within 10.5" (267mm) of the leading or trailing edge. The are several manufacturer technical white papers on the topic but was hoping for fellow spec writers’ insight. Chris Sawyer AIA CCS LEED AP Richard L Matteo, AIA, CSI, CCS Senior Member Username: rlmat Post Number: 678 Registered: 10-2003 Posted on Tuesday, August 04, 2015 - 02:55 pm:    Chris - I take it that you are talking about heat treated glass. In looking at one of my glass specs, I had a maximum roll wave distortion of 0.005", so 0.003" is even better. It also said the glass should be installed so that roll wave distortion is horizontal (parallel to bottom edge of glass). Louis Medcalf, FCSI, CCS Senior Member Username: louis_medcalf Post Number: 62 Registered: 11-2010 Posted on Tuesday, August 04, 2015 - 03:08 pm:    I have specified 0.002" for heat strengthened glass, 0.005" for tempered glass. Because of a major problem with 100 lites of tempered glass on a project some years ago, I also have this requirement: Heat-treated glass shall be free of visible mosaic or pattern optical distortion (as opposed to slight waviness noticeable when viewpoint is moving), and from defects caused by roller pick. 'Roller pick' is not covered by ASTM C1048 and is hard to quantify, but can be a serious problem. The defect causes straight lines on nearby buildings viewed through the glass to be fuzzy or pixilated in appearance. anon (Unregistered Guest) Unregistered guest Posted on Tuesday, August 04, 2015 - 04:14 pm:    Chris, Your spec is tight, and covers what it should for roller wave distortion. You might also consider millidiopter requirement of no more than +/- 100 for glass 1/4 to 3/8 inch in thickness (from Viracon guide spec). Brett Scarfino (Unregistered Guest) Unregistered guest Posted on Friday, August 07, 2015 - 03:47 pm:    You might include a glass visual mockup - project size IGUs...including the necessary heat treatment (HS or FT). This would be for review/approval (retained as an approved standard throughout the project). You could take it a step further by requiring glass fabricator production measurements to be submitted for this mockup, providing quantifiable data for your qualitative visual review. You might also include color measurements. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1636 Registered: 03-2002 Posted on Tuesday, August 11, 2015 - 11:02 am:    But, are there any glass fabricators that can actually meet this requirement? If so, what fabrication techniques are they using that others are not? Having seen heat treatment being performed a couple times, it's not clear to me how this requirement can be met. anon (Unregistered Guest) Unregistered guest Posted on Tuesday, August 11, 2015 - 12:30 pm:    John, What requirement are you asking about, specifically? Bill Coady CSI, CCPR Senior Member Username: billcoady Post Number: 23 Registered: 06-2006 Posted on Tuesday, August 11, 2015 - 01:03 pm:    Chris, Roll wave distortion and "flat" glass is a complicated topic. I haven't seen anything in this post that is way off target. With that said, I would rather have a private conversation with you about this topic so if you want to do that please email me at bcoady@guardian.com or call me at 425-823-6514. I'm not going to try to "sell" you anything but believe it would be best if we had a detailed discussion about your project, your project needs, and your owner's expectations. I'd like to know where the project is located, what type of project it is, etc. Without understanding more about your project and needs it would be wrong for me to spout off that you should have .005" or .003" maximum peak-to-valley measurement in the main body of the glass, a maximum of .008" within 10-1/2" of the leading or trailing edge, and maximum 50% of the bow/warp tolerance in ASTM C 1048. There are also other considerations such as the orientation of the roll wave lines that should be discussed and included in a specification. So........as I said, it's complicated. By the way, there are glass fabricators across North America that can achieve these performance levels. Bill Coady CSI, CCPR- Architectural Design Manager- Guardian Industries- Northwest Region Chris Sawyer, AIA CCS LEED AP Senior Member Username: csawyer Post Number: 15 Registered: 02-2009 Posted on Tuesday, August 11, 2015 - 01:24 pm:    Bill, The project is complicated by security issues that require heat-treated laminated units compounding the issue. I'll email you directly. Thanks Chris Sawyer AIA CCS LEED AP John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1637 Registered: 03-2002 Posted on Tuesday, August 11, 2015 - 02:30 pm:    Bill, I appreciate your input as a manufacturer. It's interesting to know that some fabricators can meet a "flatter" standard for glass distortion than others. Can you fill us in on what kinds of things the fabricator does, or can do, to improve flatness? Bill Coady CSI, CCPR Senior Member Username: billcoady Post Number: 24 Registered: 06-2006 Posted on Thursday, August 13, 2015 - 12:25 pm:    John, I'm not a furnace operator or engineer so please consider that when reading my comments. A good furnace operator with good equipment and a good team will work in these basic areas: *Adjust the heat zones and time sequences to optimize heat absorption in the glass without over cooking it. This means that different low E coatings and different thickness substrates will be treated differently. Each has a "recipe" and that "recipe" is different for each furnace configuration. *Adjust quench air flow to flatten the glass and to minimize roll wave, center-kink, leading and trailing edge distortion, etc. *Monitor output to assure that it meets the required specification. Many fabricators are investing in on-line systems such as Light Sentry that optically scans each heat treated lite to ensure compliance with established specification. In addition to quality fabrication and good, tight, reasonable heat treating specifications, may architects and owners are moving to thicker outboard lites. Instead of the standard 6mm (1/4") thickness found in most US projects, moving to 8mm (5/16") or 10mm (3/8") for the outboard lite will improve the flatness appearance. Projects in Europe and, to a lesser degree, Canada, regularly use thicker outboard lites. There are, of course, many other factors that contribute to a well-made, good looking insulating glass unit but this forum isn't the place for that detailed discussion. Brett Scarfino (Unregistered Guest) Unregistered guest Posted on Friday, August 14, 2015 - 09:51 am:    John - Lite Sentry's literature (http://litesentry.com/) has some good information on glass distortion, as well as sample surface distortion maps. I understand the Osprey to be the most common (and perhaps most capable). One could imagine how the heat treat "recipe" could be optimized having this sort of information. Bill Coady CSI, CCPR Senior Member Username: billcoady Post Number: 25 Registered: 06-2006 Posted on Friday, August 14, 2015 - 03:27 pm:    Brett is absolutely correct about how the on-line measurement systems are used and that Osprey is the most common, to the best of my knowledge.