Biodesign Institute brings shading solutions inside
Each 750mm deep louvre is divided vertically into four sections each of which may be operated independently.
by Jim Taggart
Solar control is one of the most critical aspects in the design of green buildings. From a building science perspective, exterior shading systems seem the logical choice as they intercept direct solar radiation before it strikes the building envelope and so effectively control heat gain.
However other considerations may come into play. Exterior louvres strongly influence the character of a building façade, particularly where continuous glazing systems are used. Shadows cast on the glass can reduce views into the building, creating an impassive architecture - an effect not always consistent with the design objectives. Yet the alternative approach of bringing the louvres inside also has its problems.
Such was the case at the Biodesign Institute at Arizona State University in Tempe, Arizona where the client was concerned about the impact of exterior louvres on the appearance of the building. With a prominent site and sweeping views of the Sonoran Desert, the university wanted the facility to appear light and welcoming to visitors - a quality workplace capable of attracting scientists of the highest calibre. This presented the joint venture architects, with a difficult challenge.
The sensitivity of scientific experiments to light and heat have tended to limit the options for the daylighting of research laboratories. The Biodesign Institute achieves its unusually high light levels through a multi-faceted approach. Plan depth is reduced by arranging program spaces around a central sky-lit atrium, and ceilings are sloped to further increase light penetration. Fixed exterior louvres have been used in some areas, but on the most prominent facades the architects used motorized interior louvers to maximize transparency and views into and out of the building.
The institute is a complex of four connected buildings, of which Buildings A and B are complete. An exterior sun screen assembly is used to shade the south wall of Building A and the west wall of Building B, and also used at high level on the east side to connect the two buildings visually.
Below it, a system of motorized interior louvres has been used. These interior louvres are 125mm deep aluminum aerofoil sections and are installed along the length of the east curtain wall façade. In the early morning the louvres close to reduce glare. As the sun rises throughout the day the blinds open to admit natural light and allow views out, before closing again at night for privacy.
The lower half of the system [which directly corresponds to the occupied zone of the building], while responding automatically to solar position, can also be controlled manually by the occupants. A desktop icon on each computer controls the louvre position, and can even override the upper louvers to protect sensitive research.
The positioning of the interior louvres relative to the curtain wall was determined by a thermal comfort study, the results of which were tested on a mock-up. The ASHRAE prediction of thermal comfort includes considerations of ambient temperature, humidity, occupant activity level and the insulation value of clothing. Also of significance is the mean radiant temperature of adjacent surfaces.
Initially, the louvres were designed to be mounted in short lengths within the 200m-deep boxes formed by the mullions and transoms of the curtain wall with incoming air “washing” down the windows from above. However, a CFD (computational fluid dynamics) analysis showed that, with the louvres in the closed position, there could be unacceptable heat build up. While cool air could be introduced between the louvres and the upper glass panel of the curtain wall, it was prevented from reaching the lower part of the wall by the transom. This resulted in high surface temperatures, excessive radiation and occupant discomfort.
With construction fast-tracked, it was too late to change the position of the perimeter in-slab air diffusers, so the team experimented with moving the louvers. The optimal solution was to have the louvers span the full width of the 3.3m office bays, coupled through holes drilled in glass fins projecting from the mullions. This configuration permitted the air movement necessary to keep surface temperatures and hence direct thermal radiation within reasonable limits. Architecturally, the long uninterrupted runs of louvres bring a strong geometric character to the workspaces while maintaining high levels of visual transparency.
The main entrance to the complex is via a two storey atrium on the north façade of Building B. Although the sun never strikes this façade at an angle greater than 30 degrees, some form of solar shading was required to counter early morning glare. Here a system of vertical wood louvres communicates the research focus of the building to those approaching along the main pedestrian spine.
The 9.5 m high louvres are mounted internally, and have an aerofoil section formed by bending plywood sheets around a light gauge steel armature. Each louver is 750mm deep and divided vertically into four sections, each of which can be operated independently. The louvres serve as an adaptable lining that is controlled manually. As people adjust these louvres, it changes the appearance on the exterior of the building creating random band patterns. These patterns are meant to be seen as abstracted protein gel arrays, one of the tools used in genetic research.
The emphasis now being placed on daylighting in sustainable design has opened up new opportunities for the designer, but has also brought new challenges, most critically the impact of the solar ray on the designed environment. Projects such as the Biodesign Institute demonstrate that we now possess both the science and the technology to maintain architectural flexibility while advancing the environmental agenda.
Jim Taggart, MRAIC , is editor of Sustainable Architecture & Building magazine.
The author gratefully acknowledges the assistance of Jay Silverberg and Barbara Hendricks of Gould Evans Architects in the preparation of this article.
Credits
- Architect: Gould Evans of Phoenix AZ, and Lord Eck Sargent of Atlanta GA in joint venture
- Mechanical Engineer: John Hill, Atlanta GA
- Horizontal Louvres: Nysan Shading Systems
- Vertical Wood Louvres: Nysan Shading Systems
- Curtain Wall Contractor: Walters and Wolfe
- Wood Louver Installation: HCI Resources
- Photos: Mark Boisclair - Timothy Hursley