OVERVIEW

Heating and cooling load calculations are the primary design basis for most heating and air-conditioning systems and components. These calculations affect the size of piping, ductwork, diffusers, air handlers, boilers, chillers, coils, compressors, fans, and every other component of the systems that condition indoor environments. Cooling and heating load calculations can significantly affect the first cost of building construction, the comfort and productivity of building occupants, and operating cost and energy consumption.

Simply put, heating and cooling loads are the rates of energy input (heating) or removal (cooling) required to maintain an indoor environment at a desired temperature and humidity condition. Heating and air conditioning systems are designed, sized, and controlled to accomplish that energy transfer. The amount of heating or cooling required at any particular time varies widely, depending on external (e.g., outside temperature) and internal (e.g., number of people occupying a space) factors.

Peak design heating and cooling load calculations, which are this chapter's focus, seek to determine the maximum rate of heating and cooling energy transfer needed at any point in time. Similar principles, but with different assumptions, data, and application, can be used when estimating building energy consumption, as described in Chapter 32, Energy Estimating and Modeling Methods.

This chapter discusses common elements of cooling load calculation (e.g., internal heat gain, infiltration, moisture migration, fenestration heat gain) and two methods of heating and cooling load estimation, heat balance (HB) and radiant time series (RTS).