NCC 2019 Volume One
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Classification
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Part F6 Condensation management (DtS)

Part F6 Condensation management (DtS)

Deemed-to-Satisfy Provisions

F6.0 Deemed-to-Satisfy Provisions

(a)

Compliance with Performance Requirement FP6.1 is satisfied by complying with Deemed-to-Satisfy Provisions F6.1 to F6.4.

(b)

Where a Performance Solution is proposed, the relevant Performance Requirements must be determined in accordance with A2.2(3) and A2.4(3) as applicable.

ACT Appendix

Explanatory information:

Explanatory information:

The intent of these requirements is to assist in the mitigation of condensation within a building. The installation of a condensation management system may not prevent condensation from occurring.

Intent

To specify the minimum construction requirements to assist in the mitigation of condensation in buildings.

Where a solution is proposed to comply with the Deemed-to-Satisfy Provisions, F6.0 clarifies that compliance with F6.1 to F6.4 will achieve compliance with FP6.1.

Where a Performance Solution is proposed, the relevant Performance Requirements must be determined in accordance with A2.2(3) and A2.4(3) as applicable. (See commentary on Part A2).

F6.1 Application of Part

The Deemed-to-Satisfy Provisions of this Part only apply to a sole-occupancy unit of a Class 2 building and a Class 4 part of a building.

Intent

To clarify that Part F6 only applies to Class 2 buildings and a Class 4 part of a building.

F6.2 Pliable building membrane

(a)

Where a pliable building membrane is installed in an external wall, it must—

(i)

comply with AS/NZS 4200.1; and

(ii)

be installed in accordance with AS 4200.2; and

(iii)

be a vapour permeable membrane for climate zones 6, 7 and 8; and

(iv)

be located on the exterior side of the primary insulation layer of wall assemblies that form the external envelope of a building.

(b)

Except for single skin masonry and single skin concrete, where a pliable building membrane is not installed in an external wall, the primary water control layer must be separated from water sensitive materials by a drained cavity.

Intent

To set out the requirements relating to pliable building membranes that are installed as a sarking.

Sarking is considered to be a pliable building membrane. All pliable building membranes must comply with AS/NZS 4200.1 and be installed in accordance with AS 4200.2. In climate zones 6, 7 and 8 pliable building membranes must be vapour permeable to assist in the transfer of moisture from the internal to the external environment. This recognises the higher level of risk associated with the build-up of internal moisture in colder climates particularly due to the inadequate ventilation of internal spaces. Any pliable building membrane must be installed with suitable provision to allow for the drainage of accumulated condensate to a drainage point external to the wall.

Where a pliable building membrane is not installed a drained cavity must be provided. Alternatively, a design can be assessed using Verification Method FV1.1.

F6.3 Flow rate and discharge of exhaust systems

(a)

An exhaust system installed in a kitchen, bathroom, sanitary compartment or laundry must have a minimum flow rate of—

(i)

25 L/s for a bathroom or sanitary compartment; and

(ii)

40 L/s for a kitchen or laundry.

(b)

Exhaust from a kitchen must be discharged directly or via a shaft or duct to outdoor air.

(c)

Exhaust from a bathroom, sanitary compartment, or laundry must be discharged—

(i)

directly or via a shaft or duct to outdoor air; or

(ii)

to a roof space that is ventilated in accordance with F6.4.

Intent

To reduce risk of condensation associated with mechanical ventilation.

F6.3 requires that kitchen, bathroom, toilet and laundry exhaust fans achieve specified minimum airflow rates. Requiring higher minimum airflow rates for laundries recognises the potential for much greater air moisture in the room and therefore the increased risk of condensation. This provision also requires that the specified exhausts discharge to the external environment or into a ventilated roof space in accordance with F6.4.

F6.4 Ventilation of roof spaces

(a)

Where an exhaust system covered by F6.3 discharges directly or via a shaft or duct into a roof space, the roof space must be ventilated to outdoor air through evenly distributed openings.

(b)

Openings required by (a) must have a total unobstructed area of 1/300 of the respective ceiling area if the roof pitch is greater than 22°, or 1/150 of the respective ceiling area if the roof pitch is less than or equal to 22°.

(c)

30% of the total unobstructed area required by (b) must be located not more than 900 mm below the ridge or highest point of the roof space, measured vertically, with the remaining required area provided by eave vents.

Intent

To set out the ventilation requirements relating to roof spaces.

F6.4 requires that a roof space be ventilated where exhausts are discharged directly into the roof space. F6.4 sets out the minimum unobstructed vented areas and locations relative to the pitch of the roof. Providing regularly distributed vents at both lower and upper levels assists in providing adequate cross flow ventilation.