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.