To limit the probability of:

• restricted air flow through the vented space, or
• excessive air flow through the insulation, which could lead to reduced thermal resistance.

This is to limit the probability of:

• condensation,
• the accumulation of moisture, or
• the formation of ice dams on sloped roofs.

This is to limit the probability of:

• the ingress of water, or
• compromised thermal performance of components intended to provide resistance to heat transfer.

This is to limit the probability of:

• 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, or
• deterioration, which could lead to compromised integrity of ceilings acting as environmental separators.

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.

To limit the probability of:

• restricted air flow through the vented space, or
• excessive air flow through the insulation, which could lead to reduced thermal resistance.

This is to limit the probability of:

• condensation,
• the accumulation of moisture, or
• the formation of ice dams on sloped roofs.

This is to limit the probability of deterioration, which could lead to compromised structural integrity of attic or roof assemblies or of elements protected by attic or roof assemblies, which could lead to harm to persons.