1. OH1
  2. OS2
  3. OH2


OH1 Indoor Conditions


[F42-OH1.1][F61-OH1.1,OH1.2,OH1.3]Applies where access is from the exterior.
[F42-OH1.1]Applies where access is from an unheated enclosed space.
[F51-OH1.2]Applies where access is from an interior heated space.


Intent 1:

To limit the probability of openings in environmental separators, which could lead to:

  • the ingress of precipitation,
  • the ingress of insects or vermin,
  • excessive heat transfer,
  • condensation,
  • the accumulation of moisture or the ingress of water backed up by ice dams,
  • drafts, or
  • the ingress of pollutants from adjacent attic or roof spaces.

This is to limit the probability of:

  • compromised thermal performance of components intended to provide resistance to heat transfer, which could lead to an inadequate control of the temperature of interior spaces or relative humidity,
  • the generation of pollutants from biological growth or from materials that become unstable on wetting,
  • deterioration, which could lead to compromised integrity of ceilings acting as environmental separators, or
  • water accumulation in interior spaces.

This is to limit the probability of:

  • negative effects on the air quality of indoor spaces,
  • the inadequate thermal comfort of persons, and
  • contact with moisture.

This is to limit the probability of harm to persons.

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