Intent 1:
To limit the probability of:
- 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.
Intent 2:
Where the intersection is between a shingle roof
and a chimney, to limit the probability of precipitation or meltwater
ingress, which could lead to damage to chimney liners from freeze-thaw
stresses, which could lead to flue gases leaking into living space,
which could lead to negative effects on the air quality of indoor
spaces [see analysis for Sentence 9.21.4.6.(1)].