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Introduction

In large commercial and residential buildings, energy management control systems (EMCS) play a major role to maintain good control of temperature, human comfort, and overall operational and energy efficiency. In a typical situation, heating, ventilation, air-conditioning, and refrigeration (HVAC&R) systems provide a central air supply at a controlled temperature and a flow rate for heating or cooling a particular unit or zone or entire building complex. The two main requirements of any HVAC&R system is first to provide satisfactory indoor comfort (temperature and relative humidity) conditions to the building housing both humans and equipment and, at the same, time minimize the overall energy consumption. Another important requirement is to prevent the spread of any chemical or biological species from any point where these species are released to the rest of the building. The primary professional organization responsible for all activities of HVAC&R systems is the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), which is located in Atlanta, Georgia, USA, and has been engaged in publishing and updating industry-wide standard handbooks such as ASHRAE (2005, 2006, 2007, 2008). It has been reported that the energy consumption due to HVAC&R systems in commercial and industrial buildings constitutes nearly half of the total world energy consumption according to Payne (1984) and Imbabi (1990b).