Green Giants: Design Community Focusing on Sustainable High Rises

Although "green" is not the first word that comes to mind when describing high-rise buildings, times are changing. The design community is beginning to embrace a trend already evident in such cities as New York, San Francisco and Tokyo.

By Robert L. Noble

Whether for residential or commercial use, building upward has become the only option for many densely populated cities, as land is limited and extremely expensive. While high-rises are one of the more inspiring architectural structures, they are often the most destructive.

Traditionally, high-rise design has focused on producing somewhat rational, engineered structural systems, resulting in "glass boxes" and "concrete cages."

Today, this focus is evolving. High-rise designers are beginning to address natural resource depletion, energy consumption, threatened ecology patterns, and global warming, while placing greater focus on occupant health, comfort and productivity.

Design Considerations

Several elements that are key to designing sustainable, bio-climatic high-rise buildings include:

• Service cores. A high-rise's service core has structural ramifications and also affects thermal performance, determining which parts will become openings and which will comprise external walls. Cores should be located on the warmer east and west sides of the building, providing buffer zones to insulate internal spaces.
  
  
• Orientation. High-rises are exposed to external temperatures and radiant heat. Arranging the building with its broader openings facing north and south gives the greatest advantages in reducing insulation and the resulting air conditioning load.
  
  
• Window openings. Generally, window openings should be orientate north and south. If not possible for aesthetic reasons, curtain walling may be used on non solar-facing facades. In temperate zones, transitional spaces can have adjustable glazing at the other face so that balconies or recesses can act as "sun spaces," collecting solar heat.
  
  
• Balconies. A window can be totally recessed to form a balcony or a small sky court, serving a number of functions. In addition to shading, placing balconies on hot elevations permits glazing to these areas.
  
  
• Transitional spaces. Located between the interior and the exterior, large air spaces and atriums serve as "in-between" zones. A louvered roof to encourage wind-flow through the inner areas of the building could shield their tops.
  
  
• Walls. External walls should be regarded as permeable, environmentally interactive membranes. In temperate climates, the external wall should be filter-like, providing insulation but openable in warm periods.
  
  
• Building plan. In addition to commercial intentions, the building plan should reflect the patterns of life and culture of the area and its climate. Focused attention should be given to the plan configuration, building depth, position and layout of entrances and exits, and means of movement through and between spaces.
  
  
• Planting and landscaping. Used for their ecological, aesthetic and cooling benefits, plants absorb carbon dioxide and generate oxygen, benefiting the occupants of the building and its surroundings.
  
  
• Passive shading devices. Solar shading is essential for glazed walls facing the sun and prevents heat penetration of the building all year round.
  
  
• Cross ventilation. Good air movement promotes heat emission from the human body surface and gives a feeling of comfort. Sky courts, balconies, atriums, and transitional spaces encourage wind flow. Side vents located at the facade's edges can operate as wind scoops, capturing and channeling wind into ceiling plenums to ventilate inner spaces.
  
  
• Insulation and heat stores. Good thermal insulation of the building skin reduces heat transfer from solar gain and loss of inside coolness. A second skin can be built over the inner wall with an air gap in between. In temperate climates, building mass can absorb solar heat during the day and release it at night. A water-spray system on hot facades promotes evaporation and cooling. Also, solar windows or a solar-collector wall can be located on the outer face of the building to collect the sun's heat.

Evolving LEED Standards

The U.S. Green Building Council's Leadership in Energy and Environmental Design rating system sets a national standard for achieving high-performance, energy-efficient, sustainable buildings. The updated Version 2.1 provides technical clarifications and streamlines the LEED certification requirements for new construction and major renovations. USGBC members and building industry stakeholders are encouraged to review the LEED Version 2.1 draft, which can be found at www.usgbc.org/LEED/leedv2-1.asp.

Significance to Public

Given the numerous residential, commercial, and mixed-use developments planned for the nation's urban cores, green high-rise design can have significant impacts on the health, productivity, and quality of life for downtown residents, professionals and visitors.

Local developers and designers should keep in mind that, as public demand increases, costs for alternative building materials and incorporation of sustainable elements will continue to decrease. Everyone will benefit from green high-rise design-from developers to office workers, residents, consumers, and the public at large.

Noble is CEO and design principal of Tucker Sadler, a San Diego-based architecture firm. He also chairs the San Diego chapters of the U.S. Green Building Council and the AIA Urban Design Committee.