BCAB #1558 - Alternative Insulation Values, Sentence 9.25.2.1.(2)

December 19, 2001

BCAB #1558

Re: Alternative Insulation Values, Sentence 9.25.2.1.(2)

Project Description

The subject building is a wood frame house. The exterior wall assembly is constructed with 38mm X 89mm studs with RSI 2.1 (R-12) fibreglass batt insulation in the stud cavity. The wall assembly also includes RSI 0.88 (R-5) polystyrene foam insulation exterior sheathing.

Reason for Appeal

Sentence 9.25.2.1.(2) states alternatives to the requirements of Table 9.25.2.1., "Minimum Thermal Resistance of Insulation" may be determined through the use of acceptable engineering principles.

Appellant’s Position

The appellant contends that ASHRAE heat transfer calculations should be an acceptable method when determining alternatives to the requirements of Table 9.25.2.1. The ASHRAE handbooks are referenced in the Environmental Separation part of the Building Code, particularly Sentence 5.2.2.1.(1) stating: Heat, air and moisture transfer shall conform to good practise such as described in the ASHRAE Handbooks. Using this method, the appellant's assembly would have an effective value greater than the effective value of a similar assembly using the insulation criteria of Table 9.25.2.1.

Building Official’s Position

The Building Official does not support alternatives to the insulation requirements of Table 9.25.2.1. derived by the use of ASHRAE calculations.

Appeal Board Decision #1558

It is the determination of the Board that ASHRAE procedures are an acceptable reference for determination of good engineering principles as referenced in 9.25.2.1.(2).

George Humphrey, Chair