Back9.25.1.2.(4)

ATTRIBUTION:

Most technical provisions of the BC Fire Code describe how the code’s objectives and functional statements are achieved. However, some provisions, like this one, do not relate directly to a code objective. The following analysis is provided to assist in understanding of the provision.

 

APPLICATION:

Position of sheet and panel-type materials relative to the thermal insulation, in buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9], where:
  • the materials:
    • have an air leakage characteristic less than 0.1 L/(s•m2) at 75 Pa,
    • have a water vapour permeance less than 60 ng/(Pa•s•m2), and
    • are installed in a building assembly that is required to be insulated (see Article 9.25.2.1.),
  • the mild climate indicator determined in accordance with Sentence 9.25.1.2.(6) is greater than 6 300, and
  • the intended use of the interior space:
    • requires the indoor relative humidity to be maintained above 35% over the heating season, and the ventilating and air-conditioning system is designed to maintain that relative humidity, or
    • will result in an average monthly indoor relative humidity above 35% over the heating season, and the ventilating and air-conditioning system does not have the capacity to reduce the average monthly relative humidity to 35% over that period.

INTENT:

To limit the application of Clause 9.25.1.2.(2)(b) and to expand the application of Part 5 to building assemblies that:
  • incorporate low permeance materials other than as cladding or on the warm side of the assembly, and
  • are more susceptible to condensation due to moderate interior relative humidity and colder exterior temperatures over the heating season or an extended heating season.