California Green Building Code (CALGreen) – Filters

Air Filter system potentially removes solid airborne particles in a specific space, if inhaled in the lungs, it is generally harmful to human health. It protects their occupants against external and internal sources of air contaminants and improve their comfort, health and productivity with clean indoor air. It filters harmful particles such as germs, dust, pollen, powder, mold, fibers, etc. To minimize the number of contaminants in the air inside the building environment and to protect equipment components from any accumulation of debris and dirt. Every commercial space needs to have proper air filtration and ventilation for safety and hygienic purposes.  

CALGreen Code Section 5.504.5.3: Filters. 

In mechanically ventilated buildings, provide regularly occupied areas of the building with air filtration media for outside and return air that provides at least a Minimum Efficiency Reporting Value (MERV) of 13. MERV 13 filters shall be installed prior to occupancy, and recommendations for maintenance with filters of the same value shall be included in the operation and maintenance manual.

Exception: Existing mechanical equipment.

CALGreen Code Section 5.504.5.3.1: Labeling. 

Installed filters shall be clearly labeled by the manufacturer indicating the MERV rating.


The intent of this requirement is to filter particulate matter from the air by the use of at least MERV 13 rated filters, thereby improving air quality for building occupants.

Compliance Method:

Specify return and makeup air systems equipment that supports MERV 13 filters and install MERV 13 filters prior to occupancy. Refer to the California Energy Code, Section 120.1 (C) for specific requirements for ventilation and indoor air quality.


Plan intake: The plan reviewer should confirm in the construction documents that filters are specified to meet MERV 13 and labeling requirements as required by the Califoria Energy Code, Part 6 and the plans and specifications, or that the specified equipment qualifies for the exception for existing mechanical equipment.

On-site enforcement: The inspector should verify that HVAC filtration specified on the approved construction document is installed or is stored on site, with proper labeling. The inspector may check a sample of installed filters to verify the MERV rating and labeling requirements. 

(Excerpted from ‘Guide to the 2019 California Green Building Standards Code Nonresidential’ – Chapter 5)

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