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Sustainable building systems require new design guidelines.

It is an exciting time to be an HVAC&R engineer or researcher because, at present, our society is highly motivated to make buildings energy efficient and environmentally friendly. This effort is different from the energy efficiency that was promoted as a result of the first energy crisis in the 1970s. For modern buildings, energy efficiency is insufficient if not accomplished with minimal impact on the natural environment. This new awareness of building environmental impacts is due to the number of buildings, which increases exponentially with the growth of human population. Therefore, new sustainable buildings are designed, built, and maintained to have low energy consumption per square foot while being integrated into the local climate. These buildings are much more difficult to design, as the integrated approach requires new design procedures that are not yet readily available. So building designers are mostly left to their own experiences and tools to create sustainable buildings--with variable success.

Systemic efforts to create design guidelines for different sustainable building technologies are underway. For example, new guidelines are available for underfloor and displacement ventilation systems. Also, new simulation tools and models are being incorporated into energy simulation and computational fluid dynamics software packages. Theses innovations are available as a result of systemic research throughout the past decade. Nevertheless, this is just a first step in introducing unconventional building systems. The research community, in collaboration with the HVAC industry, should shift current paradigms of building design, systems, and materials. An important shift would be to replace the "design day" with a "design month" or "design year" not only in the yearly energy calculations but also in HVAC system design decisions. This is evident when making decisions on integrating HVAC systems with natural ventilation via operable windows and window management procedures. It is impossible to decide if the investments in combining natural ventilation with more conventional ventilation systems are economical without calculating the seasonal energy savings, which are not yet standardized for natural ventilation.

The building envelope is another great system for building innovations, which can include novel building materials or active building envelopes that promote ventilation or collect solar energy. Recent interest in green roofs is sparking innovations for applications of biological building envelope materials. Green roofs are already being installed in buildings across the U.S. for their runoff-water retention capacity. However, integration of green roofs with conventional HVAC systems is not present because energy saving calculations for green roofs are still unreliable. Green roof energy savings come from decreased solar heat flux by evapotranspiration, shading, and insulation, which depend on water content as well as plant and soil material. All of these factors have to be taken into account when creating models designed to estimate annual energy consumption and sizing of the cooling systems for buildings with green roofs. Other than decreased roof heat flux and runoff water flow, benefits of green roofs include decreased heat island effect in cities, increased durability of roofs, improved air quality, and aesthetic appeal. Innovative building materials and HVAC systems that positively affect the performance of both energy and environmental parameters will be more pervasive in buildings as new design guidelines are developed.

J. Srebric is an associate professor of architectural engineering and adjunct professor of mechanical and nuclear engineering, Department of Architectural Engineering, Pennsylvania State University, University Park.

J. Srebric, PhD

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Title Annotation:Editorial
Author:Srebric, J.
Publication:HVAC & R Research
Geographic Code:1USA
Date:Jan 1, 2008
Words:556
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