BCAB #1849

July 16, 2020

Re: Vapour Barrier Paint applied to Spray Applied Polyurethane Insulation

Project Description

The project is house constructed under Part 9 of the BC Building Code. It is proposed that a latex vapour barrier primer be applied over ½ pound open cell foam plastic spray insulation to meet Article Required Barrier to Vapour Diffusion. The application of the ½ pound open cell foam plastic spray insulation in a roof assembly is not within the scope of this appeal.

Applicable Code Requirements

Sentences and Division A of the British Columbia Building Code 2018. Compliance with this Code shall be achieved by

a) complying with the applicable acceptable solutions in Division B (see Note A-, or

b) except as required by Sentence (3), using alternative solutions, accepted by the authority having jurisdiction under Section 2.3 of Division C, that will achieve at least the minimum level of performance required by Division B in the areas defined by the objectives and functional statements attributed to the applicable acceptable solutions (see Note A- All materials, appliances, systems and equipment installed to meet the requirements of this Code shall possess the necessary characteristics to perform their intended functions when installed in or serving a building.

Sentences and (5) of Division B of the British Columbia Building Code 2018. Vapour barriers shall have a permeance not greater than 60 ng/(Pa·s·m2) measured in accordance with ASTM E 96/E 96M, “Water Vapor Transmission of Materials,” using the desiccant method (dry cup). Where a coating is applied to gypsum board to function as the vapour barrier, the permeance of the coating shall be determined in accordance with CAN/CGSB-1.501-M, “Method for Permeance of Coated Wallboard.”

Decision being Appealed (Local Authority’s Position)

The local authority has determined the use of latex vapour barrier primer paint applied over ½ pound foamed plastic insulation may only be accepted using the application of an alternative solution, including appropriate documentation as may be required by Sentence of Division C. As relates only to the application of a vapour barrier coating applied to gypsum wallboard, an alternative solution is required when a vapour barrier coating is applied to any other substrate.

Appellant's Position

The appellant maintains that vapour barrier paint complying with Sentence, when applied over a substrate other than gypsum board, does not need an alternative solution to achieve compliance with Subsection 9.25.4.

Appeal Board Decision #1849

It is the determination of the Board that an alternative solution is not required to demonstrate Code compliance for the use of vapour barrier paint which complies with the performance criteria of Sentence, used over substrates other than gypsum board. However, in order to comply with Article of Division A, evidence may be required to indicate the system, (vapour barrier paint and the substrate), possess the necessary characteristics to perform their intended functions when installed in or serving a building.

Reason for Decision

The Code does not limit the materials used for vapour barriers, rather provides performance criteria that must be met. The vapour barrier must be compatible with the substrate it is applied to.

Lyle Kuhnert

Chair, Building Code Appeal Board