scope:

Section 2 of Standard 62.2-2019 defines the scope of the standard. The section first describes the dwellings to which Standard 62.2 applies. The section then provides an overview of the content of Standard 62.2, which consists of the issues in dwelling units that affect IAQ. The section also identifies issues that are not covered in Standard 62.2, such as those that affect thermal comfort. Finally, the section lists some reasons acceptable IAQ might not be achieved, even if the dwelling unit meets all relevant provisions of Standard 62.2.

According to Section 2, Standard 62.2 applies to dwellings in which occupants are nontransient (i.e., they occupy the dwelling unit for more than 30 consecutive days). These dwellings include one- and two-family dwellings, townhouses, and dwelling-unit portions of multifamily buildings of any height. See Figures 2-A, 2-B, 2-C, and 2-D for examples of the types of dwellings covered by Standard 62.2.

For dwelling units in multifamily buildings, Standard 62.2 covers spaces that are in the daily control of the occupants. Standard 62.2 does not apply to common areas or service areas that are not part of an individual dwelling unit. In urban areas, buildings are often mixed use, meaning that they have retail or other commercial space on the first floor and residential apartments above. See Figure 2-D for an example of a mixed-use building with dwelling units to which Standard 62.2 applies. In that example, the commercial space, meeting room, and common laundry room would not be covered by Standard 62.2. These common and commercial-use spaces are instead covered by ASHRAE Standard 62.1.

Standard 62.2 does not apply to buildings with transient occupancy, including hotels and motels. These types of buildings are instead covered by ASHRAE Standard 62.1. When the transient or nontransient status of the occupants is not clear, the intent of the facility's managers usually serves as a good indicator. Halfway houses, for example, are not typically within the scope of Standard 62.2 if the occupants reside there for 30 days or less. A building used as a group home is within the scope of Standard 62.2 if it is designed and used as a private residence for children, adolescents, or adults who cannot live with their families or on their own because of developmental or long-term psychiatric disorders, intellectual or chronic physical disabilities, or addictions. Typically, these facilities house six or more residents and at least one caregiver who is on duty at all times.

For college dormitories, the characteristics of the dwelling unit as well as its occupancy must be considered. Many dormitories are designed to be occupied for longer than 30 days. However, not all dormitories are made up of dwelling units with facilities for living, sleeping, eating, cooking, and sanitation within each unit. For example, kitchen and bathroom facilities may be shared by several occupant rooms. In this case, the entire building would be covered by Standard 62.1.

Section 2.1 of Standard 62.2 states that the impacts of chemical, physical, and biological air contaminants on IAQ are included in the standard. Standard 62.2 does not address thermal comfort, which is covered by ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy.

Standard 62.2 includes provisions for dwelling-unit and local exhaust ventilation, and it specifies minimum ventilation rates for acceptable IAQ. To improve the performance of ventilation systems, Standard 62.2 includes other provisions that cover several topics, including the following:

• Control strategies

• Sound levels

• Make-up air

• Duct design

• Isolation of garages

• Duct tightness

• Alternative compliance for some existing buildings that have no or inadequate existing local exhaust fans

According to ASHRAE, these provisions of Standard 62.2 are the minimum requirements to accommodate ordinary residential air-contaminant sources and high humidity levels indoors. Water vapor is not itself a contaminant, but high humidity levels can cause biological growth, which can become an IAQ problem.

Implementation of the provisions of Standard 62.2 does not guarantee acceptable IAQ in a dwelling. Standard 62.2 lists several possible reasons (described here in more detail):

• The provisions provide minimum standards for ventilating typical dwellings. However, a variety of conditions in dwelling units might result in higher-than-typical contaminant loads. In such cases, a compliant mechanical ventilation system might not be adequate to provide acceptable IAQ at all times. Furthermore, occupants have varying levels of susceptibility to various contaminants. For example, a person who is sensitive to one contaminant might perceive the air quality to be unacceptable even though ventilation systems are operating in accordance with the standard.

• Research has shown that occupants who are uncomfortable or under stress are more likely to object to IAQ.

• The standard does not require cleaning of outdoor air, so the mechanical ventilation system can introduce contaminated air that might result in poorer IAQ if outdoor contaminant levels are high. This situation is common in dwellings near pollution sources, such as a busy highway.

• In buildings that meet the standard's provisions, the ventilation equipment might be turned off, performing poorly, or broken because of a lack of maintenance. The standard requires the delivery of information to the owner or occupant about proper operation and maintenance of the system, but not all occupants will choose to operate and maintain their systems as designed.

• On occasion, very odorous or extremely toxic contaminants or large amounts of contaminants might be released. For example, large amounts of pesticides, burned food, indoor barbequing, local forest fires, dust storms, or high outdoor pollutant concentrations are all high-polluting conditions or events. These types of activities and conditions can release air contaminants in such large quantities that systems designed to meet minimum ventilation standards cannot keep contaminants at acceptable levels.

Unvented space heaters are permitted in some jurisdictions and prohibited in others. Although these heaters are within the scope of Standard 62.2, the standard has no provisions specific to them. Users of unvented heaters should check applicable codes and manufacturer's instructions for guidance on their use.