Air Leakage

Section 5.4 Air Leakage

5.4.1 Air Barrier Systems

5.4.1.1. Required Resistance to Air Leakage (see Appendix A.)

1) Except as provided in Sentence (2), where a building component or assembly separates interior conditioned space from exterior space, interior space from the ground, or environmentally dissimilar interior spaces, the component or assembly shall contain an air barrier system .

2) An air barrier system is not required where it can be shown that uncontrolled air leakage will not adversely affect any of

a) the health or safety of the building users,
b) the intended use of the building , or
c) the operation of building services.

5.4.1.2. Air Barrier System Properties

1) Except as provided in Sentence (2), sheet and panel type materials intended to provide the principal resistance to air leakage shall have an air leakage characteristic not greater than 0.02L/(s • m 2 ) measured at an air pressure difference of 75 Pa.  (see Appendix A).

2) The air leakage limit specified in Sentence (1) is permitted to be increased where it can be shown that the higher rate of leakage will not adversely affect any of

a) the health or safety of the building users,
b) the intended use of the building , or
c) the operation of building services.
(See Appendix A.)

8) An air barrier system installed in an assembly subject to wind load, and other elements of the separator that will be subject to wind load, shall transfer that load to the structure.

9) Except as provided in Sentence (11), an air barrier system installed in an assembly subject to wind load shall be designed and constructed to resist 100% of the specified wind load as determined in Subsection 4.1.8.

10) Except as provided in Sentence (11), deflections of the air barrier system and other elements of the separator that will be subject to wind load shall not adversely affect non-structural elements at 1.5 times the specified wind load.

11) Where it can be shown by test or analysis that an air barrier system installed in an assembly will be subject to less than 100% of the specified wind load

a) the air barrier system is permitted to be designed and constructed to resist the less load, and
b) deflections of the air barrier system and other elements of the separator that will be subject to wind load shall not adversely affect non-structural elements at 1.5 times the lesser load.

9.25.3. Air Barrier Systems

9.25.3.1. Required Barrier to Air Leakage

1)  Thermally insulated wall, ceiling and floor assemblies shall be constructed so as to include an air barrier system which will provide a continuous barrier to air leakage

a)  from the interior of the building into wall, floor, attic or roof spaces , sufficient to prevent excessive moisture condensation in such spaces during the winter, and
b)  from the exterior inward sufficient to prevent moisture condensation on the room side during winter and to ensure comfortable conditions for the occupants.  (See Appendix A.)

9.25.3.2. Air Barrier Systems Properties (See Appendix A.)

1)  Air barrier systems shall possess the characteristics necessary to provide an effective barrier to air exfiltration under differential air pressure due to stack effect, mechanical systems or wind.

9.25.3.3. Continuity of the Air Barrier System

1)  Where the air barrier system consists of an air-impermeable panel-type material, all joints shall be sealed to prevent air leakages.

2)  Where the air barrier system consists of flexible sheet material, all joints shall be

a)  sealed, or
b)  lapped not less than 100mm and clamped, such as between framing members, furring or blocking and rigid panels.

3)  Where an interior wall meets an exterior wall, ceiling, floor or roof required to be provided with air barrier protection, the air barrier system shall extend across the intersection.

4)  Where an interior wall projects through a ceiling or extends to become an exterior wall, spaces in the wall shall be blocked to provide continuity across those spaces with the air barrier system in the abutting walls or ceiling.

5)  Where an interior floor projects through an exterior wall or extends to become an exterior floor, continuity of the air barrier system shall be maintained from the abutting walls across the floor assembly.

6)  Penetrations of the air barrier system , such as those created by the installation of doors, windows, electrical wiring, electrical boxes, piping or ductwork, shall be sealed to maintain the integrity of the air barrier system over the entire surface.

7)  Access hatches installed through assemblies constructed with an air barrier system shall be weatherstripped around their perimeters to prevent air leakage.

8)  Clearances between chimneys or gas bents and the surrounding constructon which would permit air leakage from within the building shall be sealed by noncombustible material to prevent such leakage.