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The Catch-22 here is that the more accessible a program’s user interface, the less customizable it is. In the case of simulation, the less customizable the interface, the less one can simulate the complexities of reality. “What is needed—and where encouraging progress is being made—are daylighting design programs that can simulate building designs in a matter of minutes, rather than hours. This will allow both architects and lighting designers to explore ‘what-if’ scenarios,” explains Ashdown.


The old workhorse of daylight modeling, the original highly accurate ray-tracing capabilities of Lawrence Berkeley National Laboratory’s Radiance software is still being built upon today to perform highly sophisticated daylighting modeling, and is one of the few programs capable of calculating newer Illuminating Engineering Society daylighting metrics.

One other issue, notes Speer, is that optimal daylight sensor placement and dimming/ switching strategies are still manually in the hands of the designer who must evaluate the annual daylight simulations. And due to proprietary design issues and undocumented performance characteristics for daylight photosensors and daylight harvesting controllers, this makes it exceedingly difficult to optimally design systems. As far as the “Holy Grail,” which Speer describes as accurately computing energy saved from daylight dimming and switching, this remains elusive and difficult to predict using a single software program.

Image courtesy: Graeme Watt, Synthesis Design & Visualisation Limited P



Daylighting best practices suggest another 20% energy savings can be accrued with comprehensive commissioning efforts, including careful attention to sensor location, orientation, shielding and gain/fade rates.

Targeting net zero for more than 40% of the year, the Gensler-designed PNC Plaza Tower in Pittsburgh is being outfitted with a double-skin façade incorporating Starphire ultra-clear and Sungate passive low-E glazing. In addition, laminated glass and dual-insulting glass units are being fabricated by J.E. Berkowitz.


The two-layer façade will also include a motorized outer layer and manually operable inner layer of louvers to draw fresh air through the building where it will be heated and then drawn through a “chimney” shaft to be exhausted through the roof. J.E. Berkowitz CIRCLE 297


Net Zero Buildings - June 2014  

Highlighting the Path Toward Net Zero Building Design.

Net Zero Buildings - June 2014  

Highlighting the Path Toward Net Zero Building Design.