segunda-feira, 12 de outubro de 2009

HIGH-PERFORMANCE COMERCIAL BUILDING FAÇADES


Debis Headquarters, Berlin


Automated translucent glass louvers at the Environmental Building, Building Research Establishment, Garston, UK


Heat recovery


Heat extraction



Cross section through the ventilation stack (UP) and the glazed façade (DOWN).


Automated tubular grid skylight controls daylight at Munich Airport.

BACKGROUND

This study focuses on advanced building façades that use daylighting, sun control, ventilation systems, and dynamic systems. A quick perusal of the leading architectural magazines, or a discussion in most architectural firms today will eventually lead to mention of some of the innovative new buildings that are being constructed with all-glass façades. Most of these buildings are appearing in Europe, although interestingly U.S. A/E firms often have a leading role in their design. This "emerging technology" of heavily glazed façades is often associated with buildings whose design goals include energy efficiency, sustainability, and a "green" image.

While there are a number of new books on the subject with impressive photos and drawings, there is little critical examination of the actual performance of such buildings, and a generally poor understanding as to whether they achieve their performance goals, or even what those goals might be. Even if the building "works" it is often dangerous to take a design solution from one climate and location and transport it to a new one without a good causal understanding of how the systems work.

In addition, there is a wide range of existing and emerging glazing and fenestration technologies in use in these buildings, many of which break new ground with respect to innovative structural use of glass. It is unclear as to how well many of these designs would work as currently formulated in California locations dominated by intense sunlight and seismic events. Finally, the costs of these systems are higher than normal façades, but claims of energy and productivity savings are used to justify some of them. Once again these claims, while plausible, are largely unsupported.

There have been major advances in glazing and façade technology over the past 30 years and we expect to see continued innovation and product development. It is critical in this process to be able to understand which performance goals are being met by current technology and design solutions, and which ones need further development and refinement.

The primary goal of this study is to clarify the state-of-the-art of the performance of advanced building façades so that California building owners and designers can make informed decisions as to the value of these building concepts in meeting design goals for energy efficiency, ventilation, productivity and sustainability.

What is a high-performance commercial building façade?

“Glass is a remarkable material but its functionality is significantly enhanced when it is processed or altered to provide added intrinsic capabilities. The overall performance of glass elements in a building can be further enhanced when they are designed to be part of a complete façade system. Finally, the façade system delivers the greatest performance to the building owner and occupants when it becomes an essential element of a fully integrated building design. This work examines the growing interest in incorporating advanced glazing elements into more comprehensive façade and building systems in a manner that increases comfort, productivity and amenity for occupants, reduces operating costs for building owners, and contributes to improving the health of the planet by reducing overall energy use and environmental impacts. We explore the role of glazing systems in dynamic and responsive facades that provide the following functionality:

  • Enhanced sun protection and cooling load control while improving thermal comfort and providing most of the light needed with daylighting;
  • Enhanced air quality and reduced cooling loads using natural ventilation schemes employing the façade as an active air control element;
  • Reduced operating costs by minimizing lighting, cooling and heating energy use by optimizing the daylighting-thermal tradeoffs;
  • Improved indoor environments leading to enhanced occupant health, comfort and performance.

In addressing these issues, façade system solutions must of course respect the constraints of latitude, location, solar orientation, acoustics, earthquake and fire safety, etc. Since climate and occupant needs are dynamic variables, in a high performance building the façade solution must have the capacity to respond and adapt to these variable exterior conditions and to changing occupant needs. This responsive performance capability can also offer solutions to building owners where reliable access to the electric grid is a challenge, in both less-developed countries and in industrialized countries where electric generating capacity has not kept pace with growth. We find that when properly designed and executed as part of a complete building solution, advanced facades can provide solutions to many of these challenges in building design today.”

— Stephen E. Selkowitz, Building Technologies Program Head, Lawrence Berkeley National Laboratory.

http://gaia.lbl.gov/hpbf/documents/LBNL50502.pdf

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