The information requested is as follows:
- Plans must specify whether all duct systems, air handling equipment and appliances will be located within the building thermal envelope. Including a note on the plans to the effect of “All duct systems (except intake and exhaust ductwork), air handling equipment and appliances are to be located within the building thermal envelope” would satisfy this requirement.
- Alternatively, if any portion of the duct systems (except intake and exhaust ductwork), air handling equipment and appliances will not be located fully within the building thermal envelope, the following information is also required to show compliance with exceptions 2 and 3 of ORSC 1105.3:
- A plan showing the proposed pathways of all ductwork. The recommendation is to provide gray scale floor plans with heavy black lines showing the duct pathways. The plan must identify all ductwork, air handling equipment and appliances as being located either inside the thermal envelope, outside the thermal envelope or deeply buried in insulation in accordance with exception 3 of ORSC 1105.3.
- Calculation on the plans demonstrating no more than 5 percent of the HVAC system ductwork is to be located outside the thermal envelope in accordance with exception 2 of ORSC 1105.3.
Requiring this information as part of residential permit submittals proposing new HVAC duct systems, air handling equipment or appliances aligns with the City of Portland’s goal to reduce the overall time it takes a customer to receive a building permit.
NOTE: Though not a requirement, applicants are encouraged to provide separate mechanical layout drawings within each submitted plan set. Mechanical drawings will be a useful and efficient tool during the plan review phase, during construction, and to facilitate efficient field inspections.
For reference, Section N1105.3 of the 2021 Oregon Residential Specialty Code reads as follows:
N1105.3 Installation of ducts. All new duct systems and air handling equipment and appliances shall be located fully within the building thermal envelope.
- Ventilation intake ductwork and exhaust ductwork.
- Up to 5 percent of the length of an HVAC system ductwork shall be permitted to be located outside of the thermal envelope.
- Ducts deeply buried in insulation in accordance [with] all of the following:
- Insulation shall be installed to fill gaps and void between the duct and the ceiling, and a minimum or R-19 insulation shall be installed above the duct between the duct and unconditioned attic.
- Insulation depth marker flags shall be installed on the ducts every 10 feet (3048 mm) or as approved by the building official.
The State of Oregon Building Codes Division provides two technical bulletins to offer guidance on this new code requirement:
For more information, please contact Permitting Services at 503-823-7357 or schedule a 15-minute question appointment with a residential building code reviewer.