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9.32.3.13.(8)
ApplicationIntent
OH1OS1
ObjectiveOH1 Indoor Conditions
Attribution
[F42,F63-OH1.1]
Application
Application 1: 
Exhaust outlets, in self-contained heating-season mechanical ventilation systems serving single dwelling units with 5 or fewer bedrooms that are supplied with electrical power and a heating system, in buildings to which:
  • Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9], or
  • Part 6 applies [see Sentence 1.3.3.2.(1) of Division A for application of Part 6 and Sentence 6.2.2.1.(3)].
Exceptions: 
except:
  • for exhaust outlets that serve heat recovery ventilators, and
  • as stated in Sentence 9.32.3.1.(1), which applies to heating-season mechanical ventilation systems designed to comply with CAN/CSA-F326-M.
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Intent
Intent 1: 
To limit the probability of:
  • the entry of cold air into buildings (backdraft) through exhaust outlets that are subjected to positive wind pressure when fans are not operating, which could lead to the excessive cooling of exhaust ducts, which could lead to the condensation of water vapour on the exterior surfaces of such ducts, which could lead to the generation of pollutants from biological growth, or
  • the entry of vermin into buildings, which could lead to the introduction of disease organisms.
This is to limit the probability of negative effects on the air quality of indoor spaces, which could lead to harm to persons.
Intent 2: 
To exempt exhaust outlets serving heat recovery ventilators from the requirement to install backdraft dampers, on the basis that the internal resistance of the heat recovery ventilator core provides sufficient resistance to backdraft.
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