15 May 2003
Indoor Design Conditions.
2-2.2.1 Cooling. The indoor design temperature for comfort cooling will be 15
degrees F (8 degrees C) less than the 1.0 percent outdoor design temperature, but will
not be lower than 75 degrees F (24 degrees C) nor higher than 78 degrees F (26
degrees C). The indoor design specific humidity will not exceed the outdoor design
specific humidity; otherwise, the indoor design relative humidity will be 50 percent. The
indoor design temperature provided by evaporative cooling or comfort mechanical
ventilation will be 80 degrees F (27 degrees C); the above requirements for specific
humidity do not apply where evaporative cooling is used.
2-2.2.2 Heating. The indoor design temperature for comfort heating will be 68
degrees F (20 degrees C) in areas with low levels of physical activity and 55 degrees F
(13 degrees C) in areas with moderate to high levels of physical activity. The indoor
design temperature for freeze protection will be 40 degrees F (4 degrees C). Where the
indoor relative humidity is expected to fall below 20 percent for extended periods,
humidification may be added to increase the indoor relative humidity to 30 percent.
INFILTRATION. Design air distribution systems for central HVAC systems to
maintain a slightly positive pressure within the area served in order to reduce or
eliminate infiltration unless there is a valid need to maintain a negative pressure in that
INDOOR AIR QUALITY (IAQ). Ventilation for acceptable IAQ will be in
accordance with ASHRAE Standard 62.1. Successful application of IAQ principles and
criteria plays a role with regards to HVAC systems in ensuring occupant comfort and
health. Good IAQ design practice increases worker productivity.
Provide a complete IAQ analysis in each HVAC design analysis. The
analysis narrative should document a summary of all factors considered when making
design choices regarding IAQ, including alternative ventilation solutions considered and
reasons for the selection of the solution chosen. The IAQ analysis will also include a
room-by-room breakdown of the anticipated number of occupants, the amount of
ventilation air required, and any applicable adjustments such as multiple spaces factor,
intermittent or variable occupancy factor, the ventilation effectiveness factor, and any
other factors such as high relative humidity. Where adjustments to typical ventilation
rates are significant, explore design alternatives to reduce life cycle costs. Ventilation
for variable air volume systems will ensure proper ventilation rates at low and high
Provide a ventilation schedule on the drawings, perhaps combined with the
diffuser/register schedule. This schedule should assist the building occupants when
performing future renovations. List the total supply air and the number of anticipated
occupants for each room in the schedule. Add a footnote to each schedule indicating
that the number of occupants listed is for information purposes only.
Ventilation systems that are independent of the primary air supply and
distribution systems can provide benefits such as increased humidity control, reduced