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ABSTRACT
The life-cycle assessment (LCA) methodology is used in this paper to assess the environmental effects of air-handling units (AHU) over a 20-year life cycle. This assessment is based on quantify ing the consumption of resources (energy and materials), the harmful emissions into the environment (air, water, and soil), and the potential changes in the environment (climate change, acidification, and ozone production). A normal AHU, with a face velocity of 3 m/s (600 fpm), and a small AHU, with a face velocity of 4 m/s (800 fpm), are investigated with and without two types of air-to-air energy exchangers (plate and rotating wheel). The research demonstrates the following benefits of air-to-air energy exchangers: reduced energy consumption, reduced emissions to the environment, and reduced potential harmful changes in the environment. For both of the AHUs studied, these benefits are several times greater than the burdens arisingfrom the production and operation of the AHU, where the function of the AHU is to provide 2000 L/s (4200 cfm) of outdoor air to the building space for 2500 h/year, but not to condition this air. A larger AHU with an air-to-air energy exchanger of higher efficiency has the smallest harmful effect on the environment.
INTRODUCTION
Energy use in buildings has been of considerable interest for several decades, but only recently has interest in ecological aspects of buildings arisen among building owners and clients (Adalberth 1997'a, 1997b). The energy and materials used and waste produced during the construction, operation, maintenance, and demolition of buildings have significant financial and environmental implications. Since delivering outdoor ventilation air to building spaces has one of the greatest impacts on indoor air quality in many buildings and is also responsible for 30% to 50% of the energy consumed in buildings (Liddament and Orme 1998), it is the focus of this study. This paper describes a study undertaken in Finland to assess the ecological impact of ventilation units using the life-cycle assessment (LCA) methodology (Hakkinen et al. 1999).
Life-cycle assessment (LCA) deals with the impact that a product has on the environment during its entire life cycle, from production to disposal (Figure 1). This includes the extraction of basic raw materials and energy raw materials, production processes of materials and products, transportation, use, and recycle. LCA...