9.25.1.2.

(1) Sheet and panel-type materials shall be installed in accordance with Sentence (2), if the material,

(a) has an air leakage characteristic less than 0.1 L/(s∙m²) at 75 Pa,

(b) has a water vapour permeance less than 60 ng/(Pa∙s∙m²) when measured in accordance with ASTM E96, “Water Vapor Transmission of Materials”, using the desiccant method (dry cup), and

(c) is incorporated into a building assembly required by Article 9.25.2.1. to be insulated.

(2) Sheet and panel-type material described in Sentence (1) shall be installed,

(a) on the warm face of the assembly,

(b) except as provided in Sentences (3) to (5), at a location where the ratio between the total thermal resistance of all materials outboard of its innermost impermeable surface and the total thermal resistance of all materials inboard of that surface is not less than that required in Table 9.25.1.2., or

(c) outboard of an air space that is vented to the outdoors and, for walls, drained.

(3) Wood-based sheathing materials not more than 12.5 mm thick and complying with Article 9.23.16.2. need not comply with Sentence (1).

(4) Where the mild climate indicator, determined in accordance with Sentence (6), is greater than 6300, the position of low air- and vapour-permeance materials within the assembly relative to the position of materials providing thermal resistance shall be determined according to Part 5 where,

(a) 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

(b) the intended use of the interior space will result in an indoor relative humidity above 35% over the heating season and the ventilating and air-conditioning system does not have the capacity to reduce the relative humidity to 35% for any period over that period.

(5) Where the mild climate indicator, determined in accordance with Sentence (6), is less than or equal to 6300, the position of low air- and vapour-permeance materials within the assembly relative to the position of materials providing thermal resistance shall be determined according to Part 5 where,

(a) the intended use of the interior space requires the indoor relative humidity to be maintained above 60% over the heating season and the ventilation and air-conditioning system is designed to maintain that relative humidity, or

(b) the intended use of the interior space will result in an indoor relative humidity above 60% over the heating season and the ventilating and air-conditioning system does not have the capacity to reduce the relative humidity above 60% for any period over that period.

(6) The mild climate indicator (MCI) shall be calculated according to the following formula:

MCI = abs(2.5% JMT) ∙ 200 + DD

where,

abs(2.5% JMT) = absolute value of 2.5% January mean temperature, and

DD = degree-days

(7) For walls, the air space described in Clause (2)(c) shall comply with Clause 9.27.2.2.(1)(a).

(1) Sheet and panel-type materials shall be installed in accordance with Sentence (2), if the material,

(a) has an air leakage characteristic less than 0.1 L/(s∙m²) at 75 Pa,

(b) has a water vapour permeance less than 60 ng/(Pa∙s∙m²) when measured in accordance with ASTM E96, “Water Vapor Transmission of Materials”, using the desiccant method (dry cup), and

(c) is incorporated into a building assembly required by Article 9.25.2.1. to be insulated.

(2) Sheet and panel-type material described in Sentence (1) shall be installed,

(a) on the warm face of the assembly,

(b) except as provided in Sentences (3) to (5), at a location where the ratio between the total thermal resistance of all materials outboard of its innermost impermeable surface and the total thermal resistance of all materials inboard of that surface is not less than that required in Table 9.25.1.2., or

(c) outboard of an air space that is vented to the outdoors and, for walls, drained.

(3) Wood-based sheathing materials not more than 12.5 mm thick and complying with Article 9.23.16.2. need not comply with Sentence (1).

(4) Where the mild climate indicator, determined in accordance with Sentence (6), is greater than 6300, the position of low air- and vapour-permeance materials within the assembly relative to the position of materials providing thermal resistance shall be determined according to Part 5 where,

(a) 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

(b) the intended use of the interior space will result in an indoor relative humidity above 35% over the heating season and the ventilating and air-conditioning system does not have the capacity to reduce the relative humidity to 35% or less over that period.

(5) Where the mild climate indicator, determined in accordance with Sentence (6), is less than or equal to 6300, the position of low air- and vapour-permeance materials within the assembly relative to the position of materials providing thermal resistance shall be determined according to Part 5 where,

(a) the intended use of the interior space requires the indoor relative humidity to be maintained above 60% over the heating season and the ventilation and air-conditioning system is designed to maintain that relative humidity, or

(b) the intended use of the interior space will result in an indoor relative humidity above 60% over the heating season and the ventilating and air-conditioning system does not have the capacity to reduce the relative humidity above 60% for any period over that period.

(6) The mild climate indicator (MCI) shall be calculated according to the following formula:

MCI = abs(2.5% JMT) ∙ 200 + DD

where,

abs(2.5% JMT) = absolute value of 2.5% January mean temperature, and

DD = degree-days

(7) For walls, the air space described in Clause (2)(c) shall be drained and ventilated and be not less than 10 mm deep behind the cladding, over the full height and width of the wall.