Decision making | Decision making criteria | Typical scenarios and outcomes | Post-construction issues | Highlights of interviews | Round table at SCE | Workshop at SCE
Highlights of interviews made with architects, engineers, and owner representatives
Interview with Kelly Jon Andereck, Environmental Coordinator, and Bernie Gandras, Technical Director, Skidmore Owings and Merrill (SOM), Chicago, IL, January 2002.
We discussed several of the regulatory issues that architects face when doing innovative façade designs.
We should start out discussion with a quote from a recent white paper by the Development Center for Appropriate Technology (DCAT): “… the most commonly stated reasons for denying green alternatives were lack of adequate supporting information (71.4%), and insufficient technical knowledge about the alternative (53.6%).” In fact, most if not all, leading edge building technologies in the U.S. are slow to come on line because of the lack of quantifiable analysis and case study histories.
The double-skin curtainwall is a typical example of breaking through the obstacles of disinterest, fear and the unacquainted. Although a series of excellent plate books and semi-technical references have been published mostly through the European Union, no definitive case study has clearly documented the entire development, process, measurement and verification of a double skin curtain walls in the U.S..
Currently, we’re moving towards permit of a double-skin curtainwall in Massachusetts where temperature extremes are the norm and designing for winter is standard practice (we’ve been in design for over a year). The speculative office building uses approximately 93% glass, a double-pane low-e curtain wall exterior assembly, between-pane vertical blinds, and an interior monolithic clear glass. The air cavity between the interior and exterior glass layers is ventilated with room-side air and exhausted through the plenum via natural thermal buoyancy and room-side air pressure induced by the air-handling unit.
We initially championed this design because of the sound attenuation qualities, since the site is located near an airport. We made an additional assumption that the thermal characteristics could be of benefit to the overall energy performance of the building. Throughout the course of developing the envelope design, we used DOE-2.1E to conduct whole building energy simula-tions, first using gross areas and basic default values. Over time, we developed a more detailed DOE-2 model and have conducted continuous iterations with this model ever since.
The challenge of implementing this system appeared insurmountable because of the difficulty in meeting the requirements of the energy code. During design development, the state building code was amended. But unlike the state of California, this regulatory agency is only supported by a small technical staff and by an advisory committee of interested building professionals and representatives of other interested parties. In January 2001, the Massachusetts commercial energy code requirements allowed the use of whole building simulations to model the operation of the building. Its annual operating schedules were required with “…sufficient detail to permit the evaluation of the effect of system design, climatic factors, operational characteristics, and mechanical equipment on annual energy usage”. The calculation procedure was based on 8760 hours of operation and incorporated the techniques recommended in the ASHRAE Handbook, 1997 Fundamentals Volume. In addition to these requirements, the revised energy code required that the fenestration thermal indices, U-value and solar heat gain coefficient (SHGC), be determined using procedures defined by NFRC 100, 301 and/or 200.
Determining the U-value and SHGC posed problems since there is no NFRC method to determine these values for the system we were considering. We would have to exclude the benefit provided by the venetian blinds and the ventilated air cavity, if we were to use standard NFRC procedures to demonstrate conformance with the code. To obtain credit, we needed to establish compliance through technical interpretation, addendum and/or revision of NFRC 200.
As we mentioned previously, the most commonly stated reasons for denying green alternatives or in this case, a double-skin curtainwall by any regulatory body may be lack of adequate supporting information. When both NFRC 200 and the state’s energy code requirements were introduced, insufficient technical knowledge about double-skin facades prevented the state from having an alternative method to address these types of complex facades.
Consequently and in consult with the state’s energy consultant, we decided to collaborate with a EU façade curtainwall manufacturer, the Permasteelisa Group, in order to both engineer and manufacture the curtainwall system as well to demonstrate compliance with NFRC 200 through technical interpretation. Permasteelisa used their own applied software to determine the U-value and SHGC of the façade assembly. In addition and as required, a full-scale mock-up was constructed, tested and evaluated. We then sent the testing methodologies, data and supporting documentation to NFRC for validation.
References
Eisenberg, D., R. Done, L. Ishida. 2002. “Breaking Down the Barriers: Challenges and Solutions to Code Approval of Green Buildings.” Development Center for Appropriate Technology, Tucson, AZ.
Commonwealth of Massachusetts . 2001. Energy Code for Commercial and High-Rise Residential New Construction, Secretary of State, Commonwealth of Massachusetts, January 2001.
NFRC-200. 1995. NFRC-200: Procedure for Determining Fenestration Product Solar Heat Gain Coefficient at Normal Incidence, National Fenestration Rating Council, Inc., July 1995.
Question/Information: eslee@lbl.gov