Did you make it to the excellent webinar Tysen Gannon and Technical Glass Products presented during our November Live Event? There were many really good questions from "How New Building Envelope Technologies Help Deliver Sustainability Goals/LEED Points for Commercial Buildings" that we just did not have time to talk through. Our thanks to Tysen for taking time to respond.

Q. Rebecca & Terry: Can we get the links for the case studies posted somewhere?
A. Tysen: The referenced case studies can be dowloaded from the Heschong Mahone Group's website: (http://www.h-m-g.com/projects/daylighting/projects-PIER.htm)

Q. Jon: Am I wrong in stating that ICC Energy standards via using the commercial Comcheck system would like to have its glazing to have a minimum of 0.3 SHGC? If so, how does this standard compare with Channel Glass?
A. Tysen: Channel glass insulated with a 16mm panel filled with Lumira aerogel has a SHGC value of .42 and channel glass insulated with a 25mm aerogel filled panel will have a value of .31.

Q. Jon: Any stats or analysis to backup the use of steel curtainwall?
A. Tysen: Thermal performance simulations are available to substantiate the performance values of steel curtainwall systems.

Q. Nancy: Which fabrication process is more environmentally preferable, steel or aluminum?
A. Tysen: This is an excellent question and can be complex to address depending on how one defines "environmentally prefereable." One possible metric is embodied energy. The embodied energy of virgin steel is lower than that of virgin aluminum. Recycled content is also an important factor. Aluminum fenestration profiles would typically have higher levels of recycled content than specialty steel curtainwall systems, which would also reduce the overall embodied energy of the aluminum profiles. Information regarding true life cycle assessments or a comparitive LCA of aluminum and steel profiles is not presently available, however we are able to offer that TGP's supplier of steel curtainwall profiles is ISO 14000 certified for environmetal management practices in the production of these (and other) materials).

Q. Ugochukwu: How about the comparison between the Heat conduction of Aluminum and that of Stell, with respect to indoor comfort.
A. Tysen: Condensation resistance in steel systems is better than aluminum assemblies since there is nometal in the glazing pocket, as compared to aluminum systems that typically have tongues in the unheated space that can conduct heat through the wall. Heat transfer through steel is also lower than through aluminum. For an additional barrier to heat transfer, the steel system does not have metal in the cold space of the glazing pocket and it is kept completely behind the air and water gasket barrier. Depending on the glass, the Condensation Resistance Factor (CRF) for steel curtain wall ranges from 40 (45 mm wide system, stainless caps, 1” IGU / clear glass) up to 63 (triple glazed Solarban 60, argon gas-filled air spaces).

Q. Anthony: Can a channel glass system be use for a solar hot air heat system?
A. Tysen: TGP is not aware of channel glass being used for a roof mounted solar hot air heat system, but past projects in Europe have used the Profilit glass channels in ventilated facade design with a very similar design intent. A case study of this application is available here: http://www.pilkington.com/resources/facade_brochure_2005.pdf

Q. Jan: Can channel glass be used in diagonal glazing systems?
A. Tysen: Diagnonal Glazing may be possible, a review of details and layout would have to be performed to answer with certainty for a given application. Non linear applications of channel glass have been installed in the past.

Q. Jan: How is rust mitigated in steel framing systems?
A. Tysen: All galvanized steel profiles in a steel curtainwall system are located interior to the air and water barrier. The design of the system is such that all gaskets are custom fit to the steel extrusions and are continuous: the pre-gavanized steel sections do not come into contact with water in a properly installed system. Generally, SteelBuilt Curtainwall Systems are weeped through the sill of the verticals only. There are no zone dams in these steel systems, as is typical with aluminum pressure plate systems. This eliminates the need for the steel system to be weeped at every horizontal member. Pressure plates and cover caps exposed to the exterior are generally made from aluminum, but are also available in stanless steel.