TABLE OF CONTENTS Accounting for internal heat gains involves specifying the expected peak heat gain for each hour of the day for each heat source. The 24-hour internal source schedule that results is a conservative estimate of expected hourly heat gains due to lights, equipment, people, and infiltration.
Heat gains due to lights and people can be reliably estimated on the basis of rated wattage and occupancy levels. Heat gains due to equipment, however, can be overestimated by a factor of two or more by summing the rated nameplate power consumption to obtain peak equipment heat gain levels. Recent studies indicate that peak equipment heat gains for most offices are under 2 W/ft 2. Equipment heat gains based on rated power consumption often result in estimated loads in excess of 5 W/ft 2 for the same offices (Wilkins 1991).
Infiltration also is difficult to estimate. Stack effects, wind pressure, and building envelope construction must be accounted for in the calculation. Chapter 7 presents the computational procedures and data required to estimate infiltration rates for various types of buildings and environments.
The significance of the internal heat gain profiles is largely dependent on the relative magnitude of solar and conductive heat gains. Consider the case where the peak internal heat gain due to lights and equipment is increased to 5 W/ft 2 by multiplying the equipment gains by three (Table 3.3).
Both loads are constant at the peak value from 8 a.m. to 6 p.m. The...
