How is Glass Selected?

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Author Message Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1611 Registered: 05-2003 Posted on Wednesday, March 02, 2016 - 12:56 pm:    Ok, this could be a stupid question, but these days glass selection seems to be totally up to the U Value and SGHC, at least in my neck of the woods, So Florida. On a current project, the Energy Calcs came in with some pretty bizarre numbers required a double coated laminated glass or insulated glass for a 8 story apartment project with no LEED requirements. The Architect feels I should select the glass, although I have explained I am not the AoR and fortunately my agreement calls for the AoR to select products. This project will be gray glass, as cheapest configuration as possible. So why is it the Architect can not select the glass? Because of time restrictions I reached out to several glass manufacturers and the process of selection is underway, but I am curious how do my peers handle actual glass selection? Chris Grimm, CSI, CCS, SCIP, LEED AP BD+C Senior Member Username: chris_grimm_ccs_scip Post Number: 353 Registered: 02-2014 Posted on Wednesday, March 02, 2016 - 01:20 pm:    Per your agreement it sounds like you can specify gray tinted glass and the performance requirements that you normally see, require samples, ask the architect to review and send markups if needed, and let the bid pricing sort it out? I do keep an Excel file of nearly every IGU makeup that I have specified and the performance, sorted by SHGC and filterable by several attributes espcially VLT which is inversely related to SHGC the main driver, so I can list the most likely mfr/fabricators as comparable products but I still do not "select the glass", as you say it is normally the DoR who chooses the BoD product. I recommend they get samples from their preferred reps during design. I used to sit together with them and work through this, in conference with mech engineer. More and more I do not see this type of collaboration happening since the designers just are not interested and they simply want to be removed from the spec process. If it is not a public bid project that also has emphasis on aesthetics for just the right tint/low-e combo then I do not see a problem with the performance spec/samples/beg for markups/get no markups anyway approach. Chris Grimm, CSI, CCS, SCIP, LEED AP BD+C Senior Member Username: chris_grimm_ccs_scip Post Number: 354 Registered: 02-2014 Posted on Wednesday, March 02, 2016 - 01:41 pm:    U value seems to be no problem to meet but I do track that too. Mainly so the Excel file can help me for when I'm doing public projects or others where competition is important (why not all of them, but sometimes I'm directed to not deal with that can of worms) to easily be able to put in the correct range of each performance attribute that all the listed mfrs/fabricators can meet. So far I have never had them not be able to meet a required U value, but very often they can not meet each others exact SHGC/VLT combo. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1667 Registered: 03-2002 Posted on Wednesday, March 02, 2016 - 04:08 pm:    Maybe the architect won't do the selection because it is very technical and difficult to get right. On the other hand, the visual impact glass selection makes for a building's appearance is huge. This sounds like the architect asking you to pick brick. I wouldn't do it. ken hercenberg Senior Member Username: khercenberg Post Number: 989 Registered: 12-2006 Posted on Wednesday, March 02, 2016 - 10:40 pm:    I'm with John, but I know how screwed up relationships can get down your way when dealing with Architects or developers. For South Florida you have to use laminated glass anyway. Is there a new Code requirement that is forcing you to look at new configurations to meet energy requirements? I can't imagine that winter U-Value is a big deal down there. So, presuming you have to go with insulated glass with a laminated outer lite, what's the problem with putting a Low-E coating on both the #2 and #4 surfaces? Heck, if the A/E is really out of their league on this, specify the performance requirements that have to be met, say that the glass units have to match someone's gray (maybe pick a PPG or Guardian high performance glass for at least one of the two outer lites), and leave the final selection to the Contractor. Maybe ask the A/E if they care how reflective the glass is (higher reflectivity usually performs better but you really have to like the way it looks to select it). Chris Grimm, CSI, CCS, SCIP, LEED AP BD+C Senior Member Username: chris_grimm_ccs_scip Post Number: 355 Registered: 02-2014 Posted on Thursday, March 03, 2016 - 08:38 am:    Correct Ken than can be done. For deep south + EPACT before I have had a double low-e and tint combo. Jerome, you certainly will want to find out the project's criterion for SHGC usually from the mech. engineer. It could be the prescriptive requirement, or they can alter it by using a different compliance path - so the spec writer is left in the dark usually and many an architect does not know how to ask the question correctly - they might say it is .xx but 99% of the time they have an IGU in mind that they are basing that on (not in your case though), and it can really be .0x points or even .x points different from that. Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 1389 Registered: 03-2003 Posted on Thursday, March 03, 2016 - 09:35 am:    The U-factor and SHGC are prescribed in the International Energy Conservation Code (IECC) or ASHRAE Standard 90.1 if either is adopted for the jurisdiction. U-factors and SHGCs are based on Climate Zones per the IECC or 90.1. Selecting glass that just complies with the U-factor is really not enough, since the entire assembly, including framing, is required to comply. U-factors vary between entrance doors, operable fenestration, and fixed fenestration. SHGC depends on orientation of the fenestration and projection factor from shading elements, such as overhangs. Ron Geren, FCSI, AIA, CCS, CCCA, SCIP www.specsandcodes.com Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1612 Registered: 05-2003 Posted on Thursday, March 03, 2016 - 10:18 am:    The MEP for my project came up with a U value of 0.98 and SHGC of 0.73, per recommendation of a colleague I went to construct.ppg.com using the calculator I came up with an uncoated glass configuration better than MEP's criteria (SHGC of 0.53). A simple solargray laminated glass configuration. Of course its gonna cost a mint to cool these apartments, but the Developer does not care, he does not have to meet any other energy requirements...which infuriates me, but hey I am the lowly spec writer - any comments Ron or Ken or Chris. Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 1390 Registered: 03-2003 Posted on Thursday, March 03, 2016 - 10:41 am:    The FBC indicates that Florida is mostly a Climate Zone 2A and that some areas are 1A. However, requirements for fenestration are the same for both Climate Zones for the most part. So, for fenestration U-factors, here's what is required: Fixed Fenestration: U-0.50 Operable Fenestration: U-0.65 Entrance Doors: U-1.10 (Climate Zone 1A); U-0.83 (Climate Zone 2A) Fenestration SHGC is a maximum of 0.25. The SHGC can be increased 10% to 60% depending on the projection factor calculated per Section C402.3.3 and the orientation per Table C402.3.3.1. Ron Geren, FCSI, AIA, CCS, CCCA, SCIP www.specsandcodes.com Chris Grimm, CSI, CCS, SCIP, LEED AP BD+C Senior Member Username: chris_grimm_ccs_scip Post Number: 356 Registered: 02-2014 Posted on Friday, March 04, 2016 - 10:33 am:    Jerome, I have never heard of such high values being allowed, especially for SFla. Normally I see values like what Ron is saying or a tad higher if instead of the prescriptive 0.25 they decide to do a trade-off method or modeling that allows them higher SHGC as long as they insulate more to make up for it, or similar strategies. It depends on whether 90.1 is referenced directly and what edition, or IEC (or IECC?) and what edition, which might also in turn reference the 90.1 but can have more options. It depends on how the architect and engineers decide to go about the design. But I would be surprised if there was any way to work it so a SHGC of 0.73 would be allowed. Insane. Ellis C. Whitby, PE, CSI, AIA, LEEDŽ AP Senior Member Username: ecwhitby Post Number: 266 Registered: 03-2003 Posted on Friday, March 04, 2016 - 10:48 am:    Of course, the donations from the developers to the politicians at the State and local level would have no effect on any exceptions granted from National Building Codes and Standards. Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1615 Registered: 05-2003 Posted on Friday, March 04, 2016 - 12:32 pm:    Chris, it is insane, the Architect is a new client and has close ties with his Consultants, the last time I challenged one of their Consultants, I got my head handed to me. So I have to thread lightly, I expect by end of next week prior to my issuing Permit specs someone will come to their senses. But you are correct in SFL, the SHGC should never be over 0.40. Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1616 Registered: 05-2003 Posted on Friday, March 04, 2016 - 12:33 pm:    Ellis, are you on the wrong thread? I have no idea what your post has to do with this discussion? Enlighten me. Ellis C. Whitby, PE, CSI, AIA, LEEDŽ AP Senior Member Username: ecwhitby Post Number: 267 Registered: 03-2003 Posted on Friday, March 04, 2016 - 12:58 pm:    If the developer can get assemblies that do meet International Energy Conservation Code (IECC) or ASHRAE Standard 90.1, then it is likely that the local codes have been "softened" beyond all reason. Political influence is the likely cause. Otherwise how can an exterior wall with poor performing glass be selected? Of course, perhaps the building will fail it's first pass at getting a permit.