Sentence 9.32.3.1.(2)

Intent 1:

[Clauses 9.32.3.1.(2)(a) and 9.32.3.1.(2)(b)] To limit the probability that the performance of heating-season mechanical ventilation systems will fall significantly below expectations.

This is to limit the probability of:

• inadequate ventilation, or
• the inadequate control of relative humidity.

This is to limit the probability of the inadequate control of:

• indoor air temperatures,
• airborne pollutants,
• oxygen and other components necessary for breathable air, or
• condensation, which could lead to the generation of pollutants from biological growth or from materials that become unstable on wetting.

This is to limit the probability of:

• negative effects on the air quality of indoor spaces, or
• the inadequate thermal comfort of persons.

This is to limit the probability of harm to persons.

Intent 2:

[Clause 9.32.3.1.(2)(c)] To limit the probability of excessive negative pressure, which could lead to:

• the ingress of soil gases (such as methane and radon),
• the spillage of combustion products from fuel-burning appliances that are susceptible to spillage, or
• moisture ingress from the ground.

This is to limit the probability of negative effects on the air quality of indoor spaces, which could lead to harm to persons.

Intent 3:

To direct Code users to Articles 9.32.3.3., 9.32.3.7. and 9.32.3.8., for requirements regarding required components of heating-season mechanical ventilation systems in dwelling units with 5 or fewer bedrooms.