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9.26.6.1.(1)
ApplicationIntent
OH1OS2
ObjectiveOH1 Indoor Conditions
Attribution
[F61-OH1.1,OH1.2,OH1.3]
Application
Application 1: 
Materials for underlay used beneath shingles, on roofs of buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9].
Exceptions: 
except as stated in Sentence 9.26.6.1.(2), which applies to underlay used beneath wood shingles.
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Intent
Intent 1: 
To limit the probability of:
  • moisture-permeable underlay absorbing and retaining water, or
  • water- and vapour-impermeable underlay providing a surface where condensation can accumulate in roof spaces.
This is to limit the probability of long-term wetting of roof decking or sheathing, which could lead to damage to roofing, which could lead to:
  • condensation,
  • precipitation or meltwater ingress, or
  • compromised thermal performance of components intended to provide resistance to heat transfer.
This is to limit the probability of:
  • an inadequate control of relative humidity, temperatures of interior spaces or water accumulation,
  • the generation of pollutants from biological growth or from materials that become unstable on wetting, or
  • deterioration, which could lead to compromised integrity of roofs or assemblies protected by roofs.
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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