• As sure as the sun comes up in the East, every BEC or GANA Annual Meeting deals with code developments relating to energy. Tom Culp does a great job of keeping in front of this for GANA. His presentations this year highlighted several developments worth mentioning. After the “Battle for the Wall” with ASHRAE last year about reducing the window-to-wall ratio, ASHRAE’s got some other areas that will require the glazing industry’s attention over the coming months and years. Unlike the wall battle, these changes are more reasonable.

    Energy-related issues the glazing industry will need to watch include:

    Climate zone map changes

    ASHRAE 90.1 is slated for an update in 2016. Climate zone maps are changing, so if you work in areas near the borders between climate zones, you might want to look to see if your area is changing. There’s also a reduction of U-values slated to be in the 10-14-percent range in the colder zones (4-7), which Tom felt were realistic and practical. Also, solar heat gain coefficients (SHGC) in Zones 1-3 will be revised to 0.25, and possibly to 0.22 in Zone 0.

    Spandrel glass and building orientation

    There’s some discussion about using different technologies, such as highly insulated, opaque, spandrel glass to allow higher percentages in vision glass areas. Also, do different glass types and/or glazing systems need to be installed on the North / South / East / West elevations in response to different thermal constraints (mostly solar that vary by compass direction)? We’re seeing some of that now, but this will be primarily driven by the architectural design, so we’ll have to see if this practice becomes more widespread.

    Thermal bridging

    Thermal bridging will get a lot of attention in the coming weeks and years. A couple presentations, most notably that of Stéphane Hoffman of Morrison Hershfield, hit it out of the park.

    Let’s preface this by looking at a common condition of condominium projects I’ve seen over the years. Namely, designs in which the building floor slabs extend through the exterior walls, primarily to form balconies. Curtainwalls on these projects aren’t really curtainwall in the true sense because they are discontinuous, with each floor slab interrupting the curtainwall, thus becoming a series of 1-story ribbon windows, extending from the top of one slab to the underside of the floor above.

    That floor slab becomes a thermal bridge, with no thermal break between exterior and interior. HVAC systems heat the interior in winter, including that slab, which becomes a conduit for heat transfer to exterior, colder conditions. And, the reverse in summer: the sun heats the slab, which conducts the heat to the interior, where the cooling system has to deal with the load.

    A similar type of thermal bridging happens in windows and curtainwalls. When insulation in adjacent walls isn’t aligned AND tied to the thermal breaks in the window or curtainwall system, a thermal break occurs, and energy “leaks” in or out of the building. The question of how much energy isn’t known yet, but since window and curtain wall perimeters tend to be large, the loss numbers might be huge. If they are, then the logic for addressing any heat transfer in these areas will require more attention.

    Take for example a typical head, jamb or sill detail and draw a line representing the thermal separation from the glass thru the thermal break in a framing system, and then connect it to the insulation in the adjacent wall. Any time you have to lift your marker because there’s not a material to connect any two of the materials, there’s the thermal break. If the material you’re drawing a line through isn’t thermally isolated from the exterior, a thermal bridge has occurred and that portion of the wall can transfer energy through the wall system. And, for the line to be energy and material efficient, it should be straight, not zig-zag.

    Often the glass and building wall insulation don’t align, or the line you just drew zig-zags through the detail. The glass might be at the exterior of the framing system, and generally, it aligns with the thermal break in the framing. Additionally, insulation in the adjacent wall is near the back of that construction. How do you tie the two together when they don’t align? Going back to the condominium example, for the head can receiver, where’s the thermal break in the extrusion in relation to the glass? Does it align with insulation in the adjacent construction? If that adjacent construction is a floor slab, there’s no insulation, hence a bridge has occurred.

    The over–simplified answer to the thermal bridging issue would be to extend the building insulation into the glazing cavity and tie it to the glass or to the thermal break in the framing system.  That might require zig-zagging the insulation along the perimeter of the window to get it to tie to the adjacent wall insulation.

    But there’s a catch. How do you tie the two together when there’s a water barrier to be crossed? Most framing systems currently use the glass pocket as the pressure equalized or rain screen cavity to help drain water from the glazing system, tying that off to the adjacent surrounding substrates with sealant joints, or flexible flashings, etc.

    Putting insulation into the glazing cavity might be a start, and sealing it to the glass edge might become standard operating procedure in the years to come. Rigid board products come to mind, since they usually won’t deteriorate in the presence of water. But, incorporating them with a water barrier, and then tying that to the surrounding building insulation will require the system designers to be really creative.

    This is one of those issues where the extent of the problem isn’t known, but potentially can be huge. Educating the architects on how window and wall systems have to change their design intent when it comes to perimeter detailing is equally as large.

    Finally, as Tom noted when contemplating changes to standards and codes, how long they take to get adopted into the local building code is a 2-10 year window. Changes first have to get placed in the model IBC codes, then local governments have to adopt them, which is a lengthy process.

    Stay tuned sports fans: we’re in for a bumpy ride if the thermal bridging issue takes flight.

  • chairchuckSitting through 4½ days of industry trade meetings is not what I would call a vacation, even if the weather in Vegas was ideal. Hotel chairs not being the most comfortable, the joke in the hall on Sunday morning, a little more than halfway through the Glass Association of North America (GANA) Annual Meeting and Building Envelope Contractors (BEC) Conference schedule, was that we were going to see if we could find a sponsor for a Sitz pillow (remember the “doughnut” new mothers take home from the hospital?). We even came up with a name for it, in honor of Greg Carney: “The Glass Hole.” Any takers on the sponsorship for next year?

    As always, there was A LOT of ground covered.  Just two of the biggest items were:

    **Tempered glass handrails are all but gone. In some cases they will be still be permitted, but for the most part, laminated glass is going to take their place. Edge offset tolerances likely will be set by individual fabricators, much like roller distortion. The fabricators who can minimize the offset will tend to have a leg up on the competition. And, edge fabrication is another fabricator-driven issue: how to finish the edge, how will it look compared to tempered glass options (knowing the architects are going to want something to match what they’ve been used to seeing on tempered glass – you know how that goes).

    **The GANA Laminating Division will be updating their GIBs to include a post-breakage requirement. The intent is to prevent someone / something from falling through a broken glass lite. If you think about it, that’s almost a necessity. One glazing contractor I talked with mentioned that they’re seeing some of this coming to them for future work. He said caps might play a part in this since caps have to span multiple lites to aid in not only keeping the glass in the opening, but preventing fall through.

    My take on this: The typical 200-pound point load/50-pound linear load now in the codes will have a fall-through load, which will have to be verified. The laminated glass has to stay intact and remain in the opening when a load of X pounds breaks the glass, and leans on it, the equivalent of cycling it for the impact testing, similar to the large/small missile impact testing we’re all familiar with for hurricane testing. The big question is, “when?” That’s not known at this point.

    Regarding the material used to support the glass in extruded aluminum or metal shoes in exterior handrail application: There’s some question about the gypsum based fill material being compatible with laminated glass, but that doesn’t appear to be a concern. But, its deterioration when exposed to water is another matter. Substitute materials are available, but there’s a concern about epoxy being able to deal with glass and metal expansion/contraction due to thermal loading. Epoxy and polyurethane fillers are out there, but they’re more expensive. One manufacturer has a dry/continuous shim system that may be the way to go with this type of installation. Further development is likely, but make sure whatever you’re doing works long term.

    Another big topic was whether ceramic frits weaken glass. This is still early on – there are more unknowns than knowns, at this point, and experts on either side of the issue are weighing in. Some believe that adding ceramic frits is a thermal stress issue, similar to what happens to glass because of edge damage, or heat absorption. Others believe the process of firing the frit onto the glass lessens its capacity to resist wind or other loading that may be placed upon it.

    Presently, there’s a DIN/European standard that says ceramic frit weakens glass. The ASTM E1300 “Standard Practice for Determining Load Resistance of Glass in Buildings” is being reviewed to add ceramic frit to the types of glass not included (or covered) by the standard, lumping it in with the likes of wired glass, acid etched or sand blasted glass. However, that change is not likely to pass the balloting process.

    Some of the issues appear to be coming from installations in temperate climates, where daily thermal cycles are at their extremes (e.g., the glass is extremely hot during the day, and much colder at night, with that cycle duplicated over several/many days in a row).

    Confusing the issue even more is that presently not a lot of testing has been done on new glass, or for that matter, on weathered glass, to see what impact age has, if any.  Data that formed the basis of the DIN European standard hasn’t been published.  The consultants vary on their positions, and the manufacturers are not commenting yet on whether or not this is a concern. As more info becomes available, that’s likely to change with time.

    In my opinion, since most spandrel glass is at least heat strengthened for thermal loading, it may be that these materials will have to be tempered to offer a higher level of resistance. But then the question still is, as mentioned above, if the glass is first tempered before the frit is applied, does the act of heating the glass to fuse the frit to the glass weaken the compressive stresses in the glass used to determine its strength per ASTM E1300? Sounds a bit like chasing your tail, doesn’t it?

    This another one of those issues that’s developing, and the verdict’s not anywhere close to being carved in stone. For now, it might be a good idea to ask the fabricator what they know when discussing potential orders and quotes.

    Lastly: if you ever have an opportunity to listen to Jim Abbott, don’t pass it up. Jim is the major league pitcher and Olympic gold medalist born without a right hand, who rose well beyond that challenge. I don’t know where to start describing his keynote address. His parents certainly got him pointed in the right direction. And, he clearly took their lessons of perseverance to heart. His courage, determination, accountability, and trusting in himself and others –was inspiring. At the end of his talk, the room jumped to its feet; I was glad to join in.

    More later on other topics covered at Annual Conference and BEC.

  • Field Notes 26.02.2015 2 Comments

    It’s easy to write about what goes on at GANA’s Annual Conference and/or BEC after they occur. But, since the annual conference starts next week (March 5), and BEC occurs right on its shirttail, here are some interesting developments, discussions, and other items of general interest I’m looking forward to hearing about what’s happened to since the last set of meetings. Read on, and let me know what you’re looking forward to at these meetings.

    One rumbling that appears to be getting some legs: a discussion about whether ceramic frit weakens glass. Since ceramic frit is commonly specified for spandrel glass applications, this is getting some serious attention – as it should. IGMA discussed this at length last month at their annual meetings, and now it’s going to be discussed in the Tempering Division meeting.

    The Insulating Division, in conjunction with IGMA, is working on cold forming or warping glass. There’s a lot of crazy architectural designs out there that don’t want flat glass any more, but altering glass in these ways has its limits before damage occurs to the IGU edge seals.

    The Insulating Division is also putting together some recommendations for use of insulated glass units without frame members behind them. Typical cable or point supported glazing applications are doing this now. There’s no metal at the glass-to-glass joint, but some glass fabricators are not allowing the use of IGUs without a back framing member supporting the glass edge.

    As sure as the sun sets over the Olympic Mountains in Seattle (assuming it’s not raining), if the architects catch wind that frame members don’t need to be behind every glass joint, they’re going to ask (and we at TGP have had some requests) to delete the horizontals. To carry the dead load of the glass, setting blocks at the corners, hidden in the glass-to-glass joints, has to be addressed, given the common industry practice of putting the blocks at 1/8 or 1/4 points.

    Laminating glass in handrails is still pressing its way to the fore. The Canadian standard is about to be issued any day, and how that will translate to the rest of North America will be interesting. A meeting last week of GANA’s task group within the Laminating Division looked at this, but a lot of the effort has been to address the risk of falling glass. A question that needs to be addressed just as importantly is: How do the codes need to change so that someone doesn’t fall through a glass handrail?  Keeping the glass from falling and hitting pedestrians below is only one-half of a very important question, but keeping the glass intact and strong enough that someone who trips on something on a balcony, doesn’t fall through the handrail even though the glass may break.  It’s analogous to a blast or hurricane load that may result in broken glass, but doesn’t evacuate the opening, which in the case of a handrail, then prevents the occupant from being on the wrong side of the rail.

    We’re going to review a lot of these and any other points discussed during annual conference in the Technical Committee that kicks off BEC on Sunday, March 8. But, it’ll only be a cursory review. Also, Dr. Dudley McFarquhar is going to review the challenges faced in the New Parkland Hospital construction project recently completed in Dallas.

    I hope you’ll join us there.  And, please let me know if there’s any perspective you think should be represented that isn’t. We can certainly use and always appreciate the feedback, and will promise NOT to assign you to any committee. Others at GANA might entice you to do so, but I can’t speak for them.

    See you in Vegas, baby!

USGlass Magazine

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