The California Energy Commission issued a clarification today on the procedure to be used in verifying outside-airflow measurements when using an exhaust fan with an inlet damper.

The 2013 Building Energy Efficiency Standards, Section 120,1, requires outside air ventilation. Section 120.5(a)1 requires testing in accordance with the Nonresidential Appendix, Section NA7.5.1. Section NA7.5.1.2 describes the requirements for Constant Volume System Outdoor Acceptance Tests. This letter provides guidance on how this acceptance testing is to be conducted.

Where a non-residential, high-rise residential, or hotel/motel building contains a mechanical ventilation system comprised of an exhaust fan and inlet damper system, the acceptance tests for outside airflow measurements for the ventilation system are to be obtained at the location of the inlet. This is where the outside air enters the building space. A measurement at any other location, including the exhaust fan, would not provide valid results because it would measure infiltration air from other parts of the building space as part of the total airflow measurement. It would not accurately measure outside airflow.

This procedure should be followed immediately, but in any event no later than January 1, 2016.

For more information regarding this clarification, please contact Alex Pineda at (916) 654-4077 or by email at