Two-sided Structural Glazing for skylights gains popularity.
Two-sided Structural Glazing for skylights is popular in skylight design due to its water infiltration performance. This construction type. The two sloping edges of the glass unit are supported by the rafters. And retained by glazing caps. The two horizontal edges are secured to the purlins using a structural silicone joint. Typically applied from the exterior. This flush purlin detail minimizes water and dirt retention on the skylight.
Per the GANA Glazing Manual, 50th Anniversary Edition. Insulated glass units must be structurally retained on all four sides. Ideally, the horizontal edges would have two sealant joints. The weather seal would be on the edge of the unit, and the structural joint would be at the base, connecting the inboard light to the purlin.
In some cases,
it’s possible to use a single joint as both the weather seal, and the structural joint. However, this option offers many challenges. The joint must be ¼” deep minimum, it must remain at a depth to width ratio of one to one, and it must support the glass unit under wind uplift pressure. Depending on the situation, this joint may become unreasonably large to support the load. Other challenges with this setup include issues with the load path. Large joints have the possibility of coming in contact with the insulated unit’s edge seal, so this leads to compatibility issues between sealants. Also, as the load must travel from the IG unit to the purlin.
Also, designers should be conscience of this topic in the design of their skylight. If you have any questions about your skylight design, so please give us a call.
Matt Gorny, E.I.
JEI Structural Engineering Glazing Systems
Matt Gorny serves clients at JEI Structural Engineering, a Kansas City, Missouri based company focused on providing professional engineering P.E. calculations and also consulting in the United States.
JEI Structural Engineering
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