NOVEMBER 19-20, 2010

Lawrence Berkeley National Laboratory: Integrated, High Performance Facade Solutions

Introducing the appropriate tools, tests and methods early in the design process can lead to more successful building facades.  The speaker, Eleanor Lee emphasized the importance of balancing HVAC loads, artificial lighting and day lighting to achieve optimal performance. She introduced several freely-available analysis tools that can be used at different scales of facade analysis to alert designers to potential human comfort issues (glare, solar heat gain, etc.)  Among these where COMFEN, a front end for Energy Plus;  BCVTB, a middleware used to integrate Energy Plus and Radiance; and DAYSIM, a Radiance based analysis program. More detailed descriptions of these tools can be found in the analysis tools blog entry here.

Eleanor also described research and testing performed through a partnership between LBNL and the New York Times on the Renzo Piano designed headquarters building in New York. LBNL performed extensive computational analysis and built a full scale mock-up in order to advise the client on the selection of appropriate automated interior sun-shading systems and optimal calibration.

Interior view looking west from within the daylighting mockup of the NYT headquarters building. Mockup of the NYT headquarters building elevation with exterior shading provided by ceramic tubes.

The results of their research can be found here.

Eleanor concluded by sharing data from tests performed on several different internal and external shading strategies. The results of the research showed both static and automated exterior shading louvers could be used to achieve a net-zero energy project, but some means of exterior shading was necessary to reach this level of performance.


– day lighting is effective at an average of 1.5 the height of the window wall. IE. for a 9’ tall window, day lighting can be an effective light source for 15’ of room depth
– light shelves increase day lighting penetration to 2.5 times the window height while also moderating light levels for occupants located near glazing
– contrast should be less than 10:1 for monitor comfort
– double skin buildings can perform poorly when not operated and maintained properly
– automated shading devices increase performance as occupants tend to leave shades down which in turn increases the energy used for artificial lighting. Automation with override control is optimal.
– 2000 cd/m2 is the mean light level where occupants lower shades.
– both static and automated exterior shading louvers can be used to achieve a net-zero energy project but some means of exterior shading is necessary.
– white ceramic frit on glass can be a source of glare and severe visual discomfort.
– SAGE Electrochromics produces glazing systems that can be adjusted via electric current to maximize   day lighting and reduce heat gain http://www.sage-ec.com/
– BCVTB  is middleware that can be used to connect other energy simulation tools such EnergyPlus and Radiance. https://gaia.lbl.gov/bcvtb
– DAYSIM  is a Radiance based analysis program mentioned in the Q&A. DAYSIM is capable of glare analysis and is readily compatible with Ecotect. http://www.nrc-cnrc.gc.ca/eng/projects/irc/daysim.html
– COMFEN  provides a graphic interface and easy-to-read graphical/ tabular output for EnergyPlus  http://windows.lbl.gov/software/comfen/comfen.html

Much of the material covered by Eleanor can also be seen here in a talk given by fellow researchers Delia Milliron of LBL’s Materials Sciences Division and Stephen Selkowitz of the lab’s Environmental Energy Technologies Division