Spacers at Insulating Glass Units

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Author Message John Hunter Senior Member Username: johnhunter Post Number: 121 Registered: 12-2005 Posted on Tuesday, May 19, 2015 - 04:42 pm:    We're doing a structural sealant glazed curtain wall system and the question is being asked about the visibility of the spacer at the butt joints. I honestly haven't done one of these for years, so I don't have an answer for the team. We'll be using black spacers, but otherwise is there a preferred type of spacer for this application? Clear glass, 1 inch units, Solarban 70X on the #2 surface. Wayne Yancey Senior Member Username: wayne_yancey Post Number: 743 Registered: 01-2008 Posted on Tuesday, May 19, 2015 - 05:34 pm:    I recommend the warn edge spacer in the black color you selected. Check out CRL YouTube instruction video. anon (Unregistered Guest) Unregistered guest Posted on Tuesday, May 19, 2015 - 05:53 pm:    you likely don't need the performance advantage of a warm edge spacer for an SSG system. SSG systems are inherently high energy performance systems. Just go with the standard aluminum spacer with whatever color you want (black is widely available). Guest (Unregistered Guest) Unregistered guest Posted on Tuesday, May 19, 2015 - 05:52 pm:    I think Wayne means *warm* edge spacer. Your choice of spacer material will affect the performance of the unit slightly so keep that in mind. Brett Scarfino (Unregistered Guest) Unregistered guest Posted on Tuesday, May 19, 2015 - 05:57 pm:    You rarely see the spacer itself, unless you're on the interior looking at the edge of the glass. If your standing outside, looking straight at the structurally glazed mullion, you do not see the spacer; you see the primary and secondary edge seals on the IGU spacer. The primary edge sealant, P.I.B., is typically black but I have see various shades of gray. The secondary edge sealant, structural silicone, comes in all kinds of different colors...but is commonly black to match the P.I.B. Then there is the exterior silicone weatherseal between the IGUs...also commonly black. http://glassmagazine.com/article/commercial/great-glazing-sacramento-international-airport-terminal-b-1412550 the horizontals are structurally glazed - gray/light gray sealants/gaskets were used vs. the traditional black scheme. Aside from the sealants I described above, you might also see the glazing gasket that is positioned between the glass and frame as well as the main bead of structural silicone...but this depends on your framing/glazing configuration. Guest (Unregistered Guest) Unregistered guest Posted on Tuesday, May 19, 2015 - 06:04 pm:    Also, keep in mind that warm edge spacers just mean warmer than aluminum spacers. So a variety spacers can be considered warm edge. Some are plastics, some are plastic coated metals, some are different metals that conduct heat less than aluminum. Stainless steel spacers can qualify as warm edge. http://glassmagazine.com/article/commercial/defining-warm-edge-commercial-market Greta Eckhardt Senior Member Username: gretaeckhardt Post Number: 9 Registered: 08-2013 Posted on Wednesday, May 20, 2015 - 10:03 am:    The thermal conductivity of stainless steel is far lower than for aluminum, and this can make a significant difference in thermal performance of the glazed fenestration assembly. Other warm edge spacer materials may be even less conductive, but one needs to make sure they will be strong enough to transfer the wind and other loads on the glass. IECC-2012 (C303.1.3) requires certification for fenestration products in accordance with NFRC 100, which should be looked into before CD specifications are issued. Thermal simulations required for NFRC certification take into account the spacer material, and can be used to compare the relative performance of glazing with different spacers. You can ask your fenestration framing manufacturer to help obtain this information. anon (Unregistered Guest) Unregistered guest Posted on Wednesday, May 20, 2015 - 11:33 am:    Greta, Can you elaborate on your comment about the spacer needing to be strong enough to transfer "wind and other" loads on the glass? What is the issue? Is there an available spacer that does NOT do this? I have never heard of any issues and do not specify performance requirements for the spacer for IGUs. Brett Scarfino (Unregistered Guest) Unregistered guest Posted on Wednesday, May 20, 2015 - 12:55 pm:    For structural glazing, the secondary edge seal carries wind pressures (this seal is an integral part of the spacer/edge construction of the IGU). For this reason, it must be structural silicone, and it should be designed for the anticipated wind pressures. The compressive forces are not really an issue; it is the negative wind pressures / tension in the edge seals that is critical. The spacer and edge seals are tested to ASTM E2190, and this tests the durability of the hermetic seals. This is needed for IGCC certification. NFRC deals with the energy performance, and achieving the desired U-factors. The warm edge spacers are one way to "tweak" the curtain walls performance/lower the overall system U-factor. Warm edge spacers are also commonly used to meet condensation resistance; the spacer improves the frame temperatures by several degrees. John Hunter Senior Member Username: johnhunter Post Number: 122 Registered: 12-2005 Posted on Wednesday, May 20, 2015 - 01:55 pm:    As has happened in the past, I start with an aesthetic question and the responses add one or two other issues to be aware of. Thanks to Greta and Brett for identifying the structural component - we'll make sure that's addressed as well.