Attention: residential designers, builders, installers, and raters.


When constructing multifamily homes under the 2019 Building Energy Efficiency Standards (Energy Code) documentation of continuous supply or continuous exhaust ventilation installations must be accompanied by a compartment leakage (i.e., blower door) test. For many active projects, this test is not listed on the certificate of compliance (CF1R-PRF-01-E), as it is not a measure. However, the test procedure described in RA3.8 is necessary to complete the compartment leakage worksheets (MCH-24) at the installation and verification (CF2R and CF3R) stages. 

Projects modeled using compliance software prior to the release of CBECC-Res 2019.2 should be revisited immediately to clarify expectations. Energy Code plans do not need to be revised or re-registered. 

Current versions of approved compliance software make this expectation clearer. In the HERS feature summary on the CF1R-PRF-01-E form, there is a new detail under building-level verifications: "Enclosure air leakage for each dwelling unit." Note that the HERS data registries will require a user to complete the MCH-24 worksheet once a dwelling unit's MCH-27 worksheet has been started. The MCH-24 must be completed before the MCH-27 can be registered.

Two compliance options are given in Section 150.0(o)1E:

Multifamily attached dwelling units shall have mechanical ventilation airflow provided at rates in accordance with Equation 150.0-B [ASHRAE 62.2:4.1.1], and comply with one of the following subsections i or ii below. When subsection ii below is utilized for compliance, all dwelling units in the multifamily building shall use the same ventilation system type.

  1. A balanced ventilation system shall provide the required dwelling-unit ventilation airflow, or
  2. Continuously operating supply ventilation systems, or continuously operating exhaust ventilation systems shall be allowed to be used to provide the required dwelling unit ventilation airflow if the dwelling-unit envelope leakage is less than or equal to 0.3 cubic feet per minute at 50 Pa (0.2 inch water) per ft2 of dwelling unit envelope surface area as confirmed by field verification and diagnostic testing in accordance with the procedures specified in Reference Residential Appendix RA3.8.

More about this topic can be found in the Residential Compliance Manual section 4.6.3. Builders are reminded to coordinate early with installing contractors and HERS raters to plan for field tests and verifications.

The Home Energy Rating System (HERS) Program addresses problems in insulation, installation, and poor quality equipment installation for heating, ventilation, and air-conditioning (HVAC) systems. Studies have shown that the heating and air-conditioning ducts in the average home leak 30 percent of the conditioned air in the system. Incorrectly installed insulation does not provide the resistance to heat flow listed on the label.

The Energy Commission requires licensed contractors to seal and test the ducts of a home when an HVAC system is installed or replaced. After the licensed contractor seals the ducts, a HERS rater will verify the leakage amount of the duct system.


BEES Hotline

Toll-free in California: 800-772-3300
Outside California: 916-654-5106


Building Energy Efficiency Standards