© Copyright CalCERTS, Inc. 2019
Code Cycle: 2016 & 2019 Standards
Reference: 2019 CalCERTS New Construction Manual Chapter 6, Section 3
Impact: Existing HERS Test
Residential Compliance Manual
RCM 188.8.131.52 Minimum Insulation
Ducts that are entirely in conditioned space must comply with an installed R-value of R-4.2. In all other cases, the minimum allowed duct insulation value is R-6. Higher values may be required by the prescriptive requirements, as described below.
RA 184.108.40.206.8 describes the duct leakage to outside test to help ensure that the ducts are within the pressure boundary of the space being served by the duct system. Passing the test alone is not enough to establish that the ducts are entirely within conditioned space.
The test procedure is in addition to a basic visual inspection of the ducts to ensure that no portion of the duct system is obviously outside the apparent pressure/thermal boundary. Once this has been established, the leakage to outside test verifies that the pressure boundary is intact and preventing leakage from escaping to the outside.
Applying this procedure to multifamily dwelling units poses a unique situation. In this case, leakage to outside means conditioned air leaking from the ducts to anywhere outside the pressure boundary of the space being served by the duct system, including adjacent dwelling units. Duct leakage to adjacent dwelling units is not desirable and should be
eliminated. When performing the leakage-to-outside test, it is necessary only to pressurize the dwelling unit served by the duct system being tested.
RCM 220.127.116.11 Duct Location
Standard residential construction practice in California is to place ducts and associated air handling equipment in the attic. When meeting the prescriptive requirements for the Energy Standards, there are two options for where this equipment can be located:
- If meeting the prescriptive requirements of the high-performance attics (HPA), the duct system and air handlers of HVAC systems are allowed to be located in the attic.
- If meeting the prescriptive requirements of the ducts in conditioned space (DCS) as explained above, the duct system and air handlers of HVAC systems must be located in conditioned space, which includes a joist cavity between conditioned floors, or in sealed cavity below attic insulation. If the DCS requirements are to be met, additional requirements apply:
- Air handlers containing a combustion component should be direct vent (sealed combustion chambers), and shall not use air from conditioned space as combustion air. Other types of combustion heating systems are possible given the system installer adheres to the combustion air requirements found in Chapter 7 of the California Mechanical Code.
- Duct location needs to be verified through a visual inspection per Reference Residential Appendix RA18.104.22.168.3.
- Duct leakage to outside needs to be confirmed by field verification and diagnostic testing in accordance with Reference Residential Appendix RA22.214.171.124.8.
- Ducts are insulated to a level required in Table 150.1-A.
2016 & 2019 Residential Reference Appendices
RA126.96.36.199.3 Visual Verification of Ducts Located Entirely In Conditioned Space.
A visual inspection shall confirm space conditioning duct systems are located entirely in conditioned space. If any part of the space conditioning duct system is outside of conditioned space, the system does not pass.
RA188.8.131.52.8 Verification of Low Leakage Ducts Located Entirely In Conditioned Space.
A visual inspection shall confirm the duct system location as specified by Section RA184.108.40.206.3. Additionally, ducts to have less than or equal to 25 cfm leakage to outside when measured as specified by Section RA220.127.116.11.4.