Exterior Glass for Retail

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Author Message Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1389 Registered: 05-2003 Posted on Wednesday, June 10, 2015 - 01:13 pm:    For retail work the architect wants us to specify the clearest glass possible, what property is most important Light Reflectance or Light Tansmittance? Curt Norton, CSI, CCS Senior Member Username: curtn Post Number: 229 Registered: 06-2002 Posted on Wednesday, June 10, 2015 - 01:30 pm:    Jerome, if they really want clear glass, then low iron would be best. http://www.ppgideascapes.com/Glass/Products/Starphire-Glass.aspx I would think high transmittance would be the most important. Steven Bruneel, AIA, CSI-CDT, LEED-AP, EDAC Senior Member Username: redseca2 Post Number: 488 Registered: 12-2006 Posted on Wednesday, June 10, 2015 - 01:32 pm:    Transmittance achieved through low iron content. Take a look at PPG Starphire products. Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1390 Registered: 05-2003 Posted on Wednesday, June 10, 2015 - 01:35 pm:    I specified PPG Starphire, GC came back with Oldcastle Sunguard as an "equal". Alan Mays, AIA Senior Member Username: amays Post Number: 217 Registered: 02-2003 Posted on Wednesday, June 10, 2015 - 01:41 pm:    Jerome, I was told quite a while ago that they want it as clear as possible so that the colors show correctly through the glass. The trouble with the other types of glass is that there is a tint and the product does not show correctly. The low iron glass is what they should be looking at. The energy performance of the glass is terrible. Both PPG and Viracon has glass for these kind of applications. You also want the least reflective glass. You have to be able to see the product. Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1391 Registered: 05-2003 Posted on Wednesday, June 10, 2015 - 01:53 pm:    Thanks, but I still need to know what property is most important Light Reflectance or Light Tansmittance? Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 1310 Registered: 03-2003 Posted on Wednesday, June 10, 2015 - 01:57 pm:    These are the low iron glass providers. Other manufacturers, such as Oldcastle and Viracon, will use these products in their assemblies: PPG = Starphire Guardian = UltraWhite Plikington = Optiwhite Ron Geren, FCSI, AIA, CCS, CCCA, SCIP www.specsandcodes.com Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 1311 Registered: 03-2003 Posted on Wednesday, June 10, 2015 - 01:58 pm:    Jerome: The Sunguard glass that was submitted is actually Guardian's UltraWhite glass with a Low-e coating. Ron Geren, FCSI, AIA, CCS, CCCA, SCIP www.specsandcodes.com Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 1312 Registered: 03-2003 Posted on Wednesday, June 10, 2015 - 02:22 pm:    If you want the glass to look clear from the outside, then visible light reflectance should be as low as possible with visible light transmittance as high as possible. Ron Geren, FCSI, AIA, CCS, CCCA, SCIP www.specsandcodes.com Alan Mays, AIA Senior Member Username: amays Post Number: 218 Registered: 02-2003 Posted on Wednesday, June 10, 2015 - 02:27 pm:    Ultimately, the architect needs to review samples of the glass. This is something that he has to determine. Ron is correct. The low iron glass is what they want. Projection windows use this type of glass. It is expensive glass. The trouble with Low-E coatings is that can change the tint of the glass. That is why the architect should review and approve a sample. Nathan Woods, CSI, CCCA, LEED AP Senior Member Username: nwoods Post Number: 674 Registered: 08-2005 Posted on Wednesday, June 10, 2015 - 02:35 pm:    I use PPG Starfire on all my retail project display case windows Steven Bruneel, AIA, CSI-CDT, LEED-AP, EDAC Senior Member Username: redseca2 Post Number: 489 Registered: 12-2006 Posted on Wednesday, June 10, 2015 - 04:26 pm:    Only a few years back low iron glass like Starphire was considered premium, but now I see it used everywhere. Our first application 15 years ago was for an enclosed pedestrian bridge to prevent car headlights reflecting right back at the drivers. It was treated as rocket science then. But now I have an office building in construction where it is in the typical vision glass assembly. I can see the difference too. When I go home at night down busy downtown streets the ground floor retail spaces look like stage sets, brightly lit up with no noticeable glass separating them from the sidewalk. Before, you saw mostly just reflections and glare from what was going on outside. J. Peter Jordan Senior Member Username: jpjordan Post Number: 843 Registered: 05-2004 Posted on Wednesday, June 10, 2015 - 05:04 pm:    For 6 mm glass, the difference in visible light transmittance between regular clear and low-iron is 89% and 91%. I would suggest that if you put these two together in a frame side by side, you would not be able to tell the difference. Given the premium paid for low iron glass (up to 30 percent more), I think this stuff is over valued. I think if you have a loose sample, the clarity of the edge of low iron glass gives the impression that it is clearer than it is. When you put two 6 mm lites together (as you would in an insulating glazing unit), regular glass has a VLT of 79% while low iron has 83% transmittance; still pretty close. What is not specified in the original posting is whether this is exterior glazing or interior glazing. If it is exterior glazing, then you are probably going to have a low-e coating with a pretty stiff SHGC. Visible light transmittance will be important, but the reflectance is critical as well. The appropriate low-e coating should be optimized between SHGC and reflectance values. Keep in mind that the reflectance is also a function of the differential in light levels on both sides of the glass. If the "show cases" behind the glass are well lit, and the outside pedestrian area is in a deep colonnade or arcade, reflectance may be less of a concern. Richard Howard, AIA CSI CCS LEED-AP Senior Member Username: rick_howard Post Number: 289 Registered: 07-2003 Posted on Wednesday, June 10, 2015 - 07:08 pm:    Schott Amiran glass has an anti-reflective coating that is really great for retail. Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1392 Registered: 05-2003 Posted on Thursday, June 11, 2015 - 05:00 am:    Peter, this is for exterior glass. Bill Coady CSI, CCPR Senior Member Username: billcoady Post Number: 20 Registered: 06-2006 Posted on Saturday, June 13, 2015 - 06:16 pm:    Jerome, as in many things in life, the answer to your question about which is more important, VLT or Reflectance is "it depends". For high end retail where the view from outside to inside is critical or in restaurants where the view from in to out at night is primary owner's sometimes consider incorporating an anti-reflective coating. Pilkington's OptiView and Schott's Amiran are used quite often. These products tend to get VE'd out on all but the most critical, high end installations. The comments by others seem to all be pretty much on target. Ron Geren's comments about who makes UltraWhite, Starphire, and OptiWhite are correct as is his general advice about looking from outside in and having low reflectance and high VLT. The actual reflectivity and visible light transmission numbers will be dependent more on the type of low E coating used than on what the substrate is, assuming this is an Insulating Glass Unit (IGU) with some type of low E. Whether you use low iron or standard clear substrate really is a matter of evaluating samples of low iron and clear with the selected low E coating and then deciding if the difference in appearance and performance of the low iron configuration is critical and worth the added investment. A large or full size mock-up comparison would be the relatively fool-proof way to decide, of course.