Green Building Green Building
Guidelines for Design

HVAC Systems : Additional Outdoor Air Supply

HVAC Systems Introduction
Eliminate Indoor Air Pollution
Isolate and Exhaust Pollution Sources
Outdoor Air Intake Placement
Additional Outdoor Air Supply
Filter or Treat Ventilation Air
Effective Air Distribution
Eliminate CFCs and HCFCs
Energy Efficiency
ASHRAE Standard 62-1989 Table 2 sets minimum outdoor air supply rates for different occupancies, intended to ensure that the majority of occupants express no dissatisfaction with odors or experience sensory irritation. They are not intended to establish ventilation rates that ensure occupant health. The ASHRAE Standard 62-1989 outdoor air supply rates should be considered as minimum outdoor air rates supplied by mechanical systems.

Design supply air systems to allow the future supply of 150% of the outdoor air supply required by ASHRAE Standard 62-1989 Table 2. Wherever possible, provide additional outdoor air capacity in the supply air system to allow for future changes of occupancy, pollutant sources not known during design, and individuals with environmental sensitivities. Size outdoor air intake louvers and ductwork for this additional capacity, and provide space for future addition of coils, drain pans and equipment to condition this amount of air.

If air-side economizers are specified, this capacity is already inherent in the design. With the ability to provide large quantities of outdoor air, night ventilation can be used to precool building mass. This can have significant energy benefits.

  • Additional space in equipment rooms for intakes and coils may be required. May require more equipment room, duct or shaft space.
Last updated: Monday, 02/08/2010


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