• Some time ago, I did a blog about buildings that are unique and worth looking into for what they brought to the glazing world. So, nothing like pulling out the same slate again, but with a twist:  one’s a golden oldie, one’s recently completed, and one’s about to be built.  They each hold their own in what they contributed or will contribute to the industry.

    First, the eye-catching building that’s about to be built: Apple’s new headquarters: http://www.mercurynews.com/ci_24290808/apple-offers-sneak-peek-at-its-new-headquarters

    A reporter referred to it as a “spaceship – designed” structure.  The scale is huge:  a mile circumference (1/3 mile diameter) and four stories tall.  That works out to about 250,000 sq.ft. of curtainwall, at least on the exterior, and probably two-thirds of that on the interior side.

    The claim the building will be as innovative as any other Apple product can only be proved over time. It will be interesting to see how it’s received in the architectural press after it’s built, and whether it lives up to all the things the designers want it to do, like reducing air conditioning needs for 70 percent of the year and using 30 percent less energy that a typical Silicon Valley corporate building.  Two thoughts come to mind:  1) I’d like to get the glazing contract, and 2) if I worked there, I don’t think I’d enjoy walking to a meeting on the other side of the building.

    Now, let’s look at a classic all-glass building: Philip Johnson’s Crystal Cathedral in Garden Grove, Calif.  The former pastor there, Dr. Robert Schuller, started his ministry conducting services in a drive-in movie theater, and the building has what I describe as a hangar door that opened to allow those who still came to church in their cars to remain in them.

    This building is a towering symbol of 1970s architecture, with eight walls and the roof glazed over a steel space frame that limits interior structure, thereby enclosing a large, uninterrupted interior space.  Glazed with reflective glass (the product of choice in the halcyon days of yore and before low-E), the space is open, almost like being outside. At the time, it was one of the largest single structural silicone glazing jobs on the books.  The space frame and glazing were designed for an 8.0 magnitude earthquake.  I believe LOF was the glass manufacturer.

    This building was under construction just as I came out of school. You can see some good interior and exterior shots of it here.

    More recently, SOM completed the Christ the Light Cathedral in Oakland, Calif.:  http://www.youtube.com/watch?v=CNKlR_jkEo4.  Talk about the use of natural lighting!  The silhouette of Christ above the alter is actually metal panels with a dot pattern with a variety of different hole sizes and spacing that’s backlit by the exterior wall behind it.  Even the interior spaces are designed to appear as if they are naturally lit, even though the lights are clearly visible.  It’s easy to see why this building is getting so many accolades in the construction and architecture circles.

    One thing that jumps out with all of these projects, especially the last two is this: think about the radical change to these buildings if ASHRAE had its way and limited the glazing to 30 percent (knowing that the 40 percent vs. 30 percent limit probably isn’t applicable to these types of building).  It’s nice to see architects take on such unique challenges that open up their facades to let the sun shine in.  Hopefully, the glass biz will continue to help them along the way.

  • Look for ghouls, goblins and super heroes on your doorstep tonight, but don’t expect many miniature suit-wearing insurance underwriter wannabes.

    I’ve seen several comments recently regarding whether safety glass installed in storefronts prior to 1977 should be replaced, or if it is grandfathered. I’m surprised this situation isn’t caught and resolved through insurance underwriting.

    Don’t the insurance companies weigh in on liability insurance and inspect a business’s premises the same way they do homes? When my wife and I bought our current home, we had to schedule the insurance people to walk through it before closing so they could confirm the roofing type, distance to a fire hydrant and other details. They even pointed out one or two things that needed to be done in order for them to carry the policy.

    Isn’t this same thing done with business insurance coverage? For example, it seems like a lot of the reduction in job-related injuries over the years has been insurance-driven. The insurance carriers come in, inspect the premises, make recommendations for changes and underwrite what’s being done correctly. It’s a pretty pro-active process, making changes before someone gets hurt, not afterwards. I wonder if the storefront glass in a restaurant, in the old hardware store downtown, at Bill’s Barber Shop on the square, etc., is one of the things insurers inspect when they walk the premises.

    I’m not advocating that insurers be the safety police; it’s just curious how potential code compliance problems end up getting past them.

    On a different note, I was glad to see that the recent ill-informed suggestion to use wired glass as a bullet-resistant material was spit back out as quickly as it was put out there as the hokum it is. I was proud to see the reaction from some of our industry people who know the ins and outs of glass. Traditional wired glass is not impact or bullet-resistant, so it is not really a defense against school intruders.

    Compared to annealed glass, traditional wired glass was considered 50 percent weaker than annealed glass in some of the older codes. The wiring isn’t all that strong. I get the fact that the wires might remain captured around the edges, and that might be a deterrent. But with a gun, how does it block any subsequent shots after the first one that shatters it? The wire’s not strong enough or sufficient to stop bullets on its own. And the self-described “expert’s” statement didn’t come with any backup or testing, just that the wire had stayed in the opening.

    Lastly, in honor of Lyle Hill and his quotes of the week, I offer this one I heard recently from Loren Supp, AIA, lead designer with Gensler in Seattle: “Architects try to take science and synthesize it into art.”

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  • Or so I thought. Someone asked me recently if I knew how large a piece of glass needed to be to resist a certain wind load. I don’t know why I remembered I had it, but a chart from the 1970 UBC used to be what was used to figure out if glass was strong enough for wind loads.To use the chart, you found where the the thickness of the glass shown along the top row intersected with the wind load column on the left. That number was the maximum square footage of glass allowed for that wind load. Example: ¼-inch glass, 40psf wind load = 27 sq.ft. maximum glass lite size, regardless of the height and width. These values represented a “fresh off the float line” strength of annealed glass.

    Referring to another table, you could then increase the 27-square-feet allowable lite size by incorporating it into an insulated unit (27 x 1.5 = 40.5 sq.ft.), heat strengthening it (27 x 2 = 54 sq.ft) or tempering it (27 x 4 = 108 sq.ft). The factors could be combined, such that a heat strengthened, insulated unit could be, at 40 psf, 27 x 1.5 x 2 = 81 sq.ft. That’s assuming, too, if you heat treat one lite, both lites in the IGU had to be heat treated one way or another.

    These charts were developed primarily by glass manufacturers. Easy, right? Not so fast, kemosabe!

    The good folks at ASTM came along and developed ASTM E1300 “Standard Practice for Determining Load Resistance of Glass in Buildings,” which addressed more factors. According to Bill Lingnell, the old UBC charts didn’t take into account weatherability, and they used a statistical probability method following a normal distribution curve. By contrast, ASTM E1300 was developed using a failure prediction method, and also accounted for glass weathering. The IBC since has generally adopted ASTM E1300 as the glass strength standard.

    Currently, there are a lot of companies offering ASTM E1300 software that will confirm the glass construction – insulated or monolithic, heat treated or not, laminated, etc. – and whether it will work for a given wind load.

    Some programs will also calculate how much the glass deflects. If you’ve ever been in a completed building, and the occupants call in with a complaint that “the glass is about to fall out,” you know about this part of the discussion. Occupants aren’t used to glass that moves like a trampoline under certain exterior wind conditions. Glass deflects equally when annealed, heat strengthened or tempered. It takes approximately four times the force to break a tempered lite compared to one that was annealed, but both still deflect the same under the same load.

    Some architects ask about limiting the glass deflection to 1 inch. This is a human comfort thing, as there’s nothing in the codes and/or in the glazing industry that limits deflection. In most instances, the means to limit deflection on larger lites or in areas with greater wind load is to increase the glass thickness. Most framing systems don’t easily accommodate varying glass thicknesses (i.e. 1” IGU in typical vision areas, 1¼” thick in higher wind load zones). Vision and spandrel glass thickness differences used to be a common practice, but have virtually disappeared due primarily to energy constraints. The software, too, will allow one lite to be different than the other, be it tempered, heat strengthened, or laminated while the other lite stays annealed. The UBC charts didn’t do that.

    But that’s all the software will tell you. It won’t reveal whether the glass needs to be tempered, or if safety glazing is needed because it’s in a door, is adjacent to a door, or because it is adjacent to a walking surface where no handrail or horizontal is present. It also won’t tell you that safety glazing is required if the sill is lower than a certain height off the floor, or if there’s a horizontal or handrail 3’-0” to 3’-4” off the floor so that if the glass breaks, someone won’t fall through the opening.

    Software also won’t tell you if the glass should be heat treated at inside corners for sun-facing surfaces. Glass doesn’t always allow all of the sun’s energy to pass through it, some is reflected, and if that reflection is onto another glass surface, the lite on that adjacent surface may need to handle more than just direct thermal energy. Reflective metal panels may have reflective effects on adjacent glass, also.

    Other factors that affect glass substrate selection or make-up are reflective coatings and tintings, to name a few.

    The lesson here is you can trust software, just know what it’s doing, and more importantly what it’s not telling you. Although many of the old rules don’t work as well as they used to, one that still holds true is: when in doubt, call the glass manufacturer. Their tech staffs are able to help with these types of issues. It’s nice to have a second set of eyes to help get your project right, both in the estimating and execution phases.

    Lastly, PLEASE NOTE: Any comments on this blog that deal with my age, especially from Greg Carney, will be deleted with prejudice!

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