© Copyright CalCERTS, Inc. 2019
Code Cycle: 2016 & 2019 Standards
Reference: 2019 CalCERTS New Construction Training Manual Chapter 6, Section 2
Compliance Form: CF3R-MCH-29-H
Verified Duct System Design
A well designed and installed duct system saves energy by having fewer ducts, shorter duct runs, higher duct R-value, ducts located in beneficial locations and improved airflow. Therefore, a compliance credit is available for the installation of duct systems to a layout based on an approved design methodology. The Verified Duct System Design Credit is also a prerequisite verification for duct surface area reduction and special R-value Compliance Credits (buried ducts and deeply buried ducts).
An installed duct system meets the Verified Duct System Design compliance criteria if it conforms to a duct design layout that meets all applicable requirements in RA184.108.40.206.1, summarized below and is verified by a HERS Rater per RA220.127.116.11.1.4. HERS verification requires a site visit after the HVAC system has been completely assembled but before sheetrock and insulation have been installed. Design and documentation requirements include the following details:
Duct Design Layout
The duct system design shall be documented on the Duct Design Layout, a scaled layout drawing that identifies the location of the space conditioning equipment, all supply and return registers/grilles, the size, R-value, and location of each duct segment. The Duct Design Layout shall incorporate all other duct details reported on the registered Certificate of Compliance, such as buried, deeply buried, not buried, etc.
The duct system design shall be based on an industry standard design methodology such as ACCA Manual D or an equivalent. There should be a statement on the plans indicating the methodology used.
Duct Design Layout Approval
The Duct Design Layout shall be included with the building design plans and the registered Certificate of Compliance (CF1R) submitted to the enforcement agency in conjunction with the application for the building permit. A copy of the Duct Design Layout approved by the enforcement agency shall be posted or made available with the building permit(s) issued for the building, and shall be made available to the enforcement agency, installing contractor, and HERS rater for use during the installation work and for all applicable inspections.
HERS Field Verification of Installation
The location of all supply and return registers shall be verified by inspection of the interior of the dwelling unit. The location of the space conditioning equipment and the size, R-value, and location of each duct segment shall be verified by observation in the spaces where they are located. Deviations from the approved Duct Design Layout shall not be allowed without a revised a Duct Design Layout approved by the enforcement agency.
In addition to matching the approved Duct Design Layout, during Field Verification, the HERS Rater should also confirm that the installed ductwork has no sharp bends, compressions, or other obvious installation defects and is constructed with approved ducting materials. Proper design is the first step but installed performance is the true measure of efficiency gains.
Example: HVAC Duct Design Layout