TABLE OF CONTENTS Infiltration has already been discussed. However, most building codes require positive ventilation in public buildings, with a fixed ventilation rate which relates to occupancy. While older codes used rates of 5 to 10 ft 3/min per person, current requirements use two or three times that amount. Most local building codes use all or part of ASHRAE Standard 62 as a basis. This Standard undergoes continuous modification the current issue is dated 2001. Some codes may allow for automatic adjustment of outside air quantities, based on measurement of indoor air quality. Measured values may include CO 2 and/or volatile organic carbons (VOC) as appropriate.
In addition, many processes require large amounts of exhaust, for which makeup air is required. Outside air for ventilation and makeup must be introduced through an air-handling unit, where it can be filtered and tempered (brought to design condition for heating or cool- ing). This whole matter is further complicated by the knowledge that outdoor air quality may not be acceptable in many indoor environments, so that special treatment to remove contaminants may be necessary (see Chaps. 5 and 21).
Thus, while the ventilation load is not a part of the space load, it is reflected in the air-handling unit and central plant capacity. For heating, it is the minimum outside air quantity multiplied by the design temperature difference and the proper air factor. Thus,
| (3.7) |  |
where <i class="emphasis">q</i><sub<i class="emphasis">h</i></sub> = ventilation load for heating, Btu/h<i class="emphasis"> t</i><sub<i...
