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9.19.2.1.(3)
ApplicationIntent
OH1OS2OH2
ObjectiveOH1 Indoor Conditions
Attribution
[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.
Application
Application 1: 
Closures for access hatches to attic or roof spaces that measure:
  • not less than 3 m2 in area,
  • not less than 1 m in length or width, and
  • not less than 600 mm in height over an area that is not less than 3 m2 and not less than 1 m in length or width.
This applies where access to attic or roof spaces is:
  • from the exterior,
  • from interior heated space, or
  • from unheated enclosed space (e.g. garage).
This applies in buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9].
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Intent
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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