ABSTRACT This paper describes the sustainability concept of HVAC systems and discusses how underfloor air conditioning systems can be used to enhance the sustainability performance of commercial buildings. Possible benefits, flexibility and economic issues of underfloor air conditioning are discussed. Important design considerations of such approach are explained. Like many other sustainable features or HVAC technologies, careful planning and holistic design are needed to effectively apply underfloor air conditioning in the building. The benefits of the underfloor approach can be fully recognized when all the influencing factors in the building life cycle are taken into account, including construction costs, life cycle costs, controllability, indoor air quality, and energy performance. Keywords: Sustainability of buildings, HVAC systems, underfloor air conditioning. 53437
1. INTRODUCTION Sustainability of heating, ventilating and air conditioning (HVAC) systems has become a growing concern for building owners and building designers (Hui, 2001). Usually, the energy intensity of buildings is mostly in the HVAC systems that create indoor comfort by compensating for outdoor climatic conditions. Sustainability principles and green building performance characteristics are pushing building designers to investigate climate-responsive designs and innovative HVAC systems. New strategies for providing comfort in buildings are progressing rapidly but still have much room for improvement. A new approach to provide air conditioning in buildings is to make use of a raised access floor for air distribution. This concept of underfloor air conditioning has been studied and implemented in many green or sustainable building projects in a number of countries around the world. Underfloor air conditioning systems are becoming a popular alternative to traditional overhead systems for many office and commercial buildings in Japan, Europe and USA (Matsunawa, Iizuka and Tanabe, 1995; Sodec and Craig, 1990; McCarry, 1998; Terranova, 2001). The use of raised access flooring systems for office environments, whose cavity can be used as a supply air plenum, has become much more frequent in recent years (Loudermilk, 1999). These underfloor air conditioning systems can provide opportunities for improving space ventilation and reducing installation and operating costs. This paper describes the sustainability concept of HVAC systems and discusses how underfloor air conditioning systems can be used to enhance the sustainability performance of commercial buildings. Possible benefits, flexibility and economic issues of underfloor air conditioning are discussed. Important design considerations of such approach are explained. It is hoped that better understanding of underfloor air conditioning systems can be developed and suitable application of the systems can help enhance the sustainability performance of buildings.
2. SUSTAINABILITY OF BUILDINGS AND HVAC SYSTEMS Sustainability of buildings covers a wide range of issues including economy of resources, building life cycle design and humane design factors. To achieve sustainable and better performance buildings, it is important to consider the various aspects of building design and their interrelationship holistically and systematically. In most commercial buildings, the HVAC system is a key component determining the quality of the indoor environment and the economy of the building project. HVAC system design is a key feature of sustainable buildings and the equipment associated with climate control, such as fans, pumps, motors, ducts, pipes, etc., significantly affect capital and operating costs, energy use, indoor air quality, and environmental impact. Thus, HVAC systems will greatly impact how “sustainable” or “green” a building is (Hui, 2001).
To enhance the sustainability, consideration of the building life-cycle is vital, as all too often energy-saving and sustainable design features are rejected to reduce capital cost, thereby increasing energy use and total cost of ownership. In addition, pressures to complete projects on time and under budget regularly might produce decisions that are penny-wise but pound-foolish. A good example is the design for flexibility to accommodate future changes in the building. If modular planning and flexible building infrastructures for HVAC are not used due to a higher first cost, then significant penalties in operating costs might be incurred over the whole life cycle of the building. Sustainable design requires an integrated, whole-systems approach to succeed and innovation is often needed to formulate effective design solutions. But unfortunately, traditional HVAC design process is often separated from architectural design process and many HVAC designers are reluctant to innovation. Unfamiliar approaches, new and more efficient technologies, and innovative designs are frequently rejected lest they slow a project down or increase the risk to one of the participants. To achieve sustainable buildings, it is important to put HVAC design and system selection in a more integrated, open-minded perspective. 3. UNDERFLOOR AIR CONDITIONING SYSTEMS Underfloor air conditioning systems were introduced first in 1950s in Europe for rooms with high heat loads (typically 190 to 950 W/m2) such as computer rooms, control centres and laboratories; then later in 1970s, offices in South Africa, Germany, Japan and USA adopted these systems to cope with modernisation and increasing use of electronics equipment. An underfloor air conditioning system is set up based on a raised-access flooring system that is supported on vertical supports approximately 300 to 400 mm above the slab floor. The concept of underfloor air distribution has been implemented and studied in Japan, Germanyand USA (Hanzawa and Nagasawa, 1990; Sodec and Craig, 1990; Bauman, Pecora and Webster, 1999). A famous bank building in Hong Kong has also adopted a ducted underfloor air distribution system since 1984. 利用地板下的空气提高建筑的可持续性空调系统英文文献和中文翻译:http://www.751com.cn/fanyi/lunwen_57541.html