Introduction

The houses in the past were built to keep the rain, snow, and thieves out with hardly any attention given to heat losses and energy conservation. Houses had little or no insulation, and the structures had numerous cracks through which air leaked. We have seen dramatic changes in the construction of residential and commercial buildings in the 20th century as a result of increased awareness of limited energy resources together with the escalating energy prices and the demand for a higher level of thermal comfort. Today, most local codes specify the minimum level of insulation to be used in the walls and the roof of new houses, and often require the use of double-pane windows. As a result, today’s houses are well insulated, weatherproofed, and nearly air tight, and provide better thermal comfort.

The failures and successes of the past often shed light to the future, and thus we start this course with a brief history of heating and cooling to put things into historical perspective. Then we discuss the criteria for thermal comfort, which is the primary reason for installing heating and cooling systems. In the remainder of the chapter, we present calculation procedures for the heating and cooling loads of buildings using the most recent information and design criteria established by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE), which publishes and periodically revises the most authoritative handbooks in the field. This chapter is intended to introduce the readers to an exciting application area of heat transfer, and to help them develop a deeper understanding of the fundamentals of heat transfer using this familiar setup. The reader is referred to ASHRAE handbooks for more information.