Is mechanical ventilation (in accordance with Section 403) required by Section 401.2 in either of the following examples:
1) In an R-2, R-3, or R-4 dwelling unit regardless of the number of stories where blower door test results are greater than or equal to 3 air changes per hour and natural ventilation in accordance with Section 402 is provided for the occupied space(s)?
2) In the dwelling units of an R-2 regardless of the number of stories where the building thermal envelope complies with Sections C402.5.1 through C402.5.8 and natural ventilation in accordance with Section 402 is provided for the occupied space(s)?
Interpretation #8703
Published December 02, 2022
Original Request
- Code Version
- 2021
- Code
- MECHANIC
- Code Description
- Chapter
- Section
- 401.2
- Topic
- Mechanical and Natural Ventilation
Question
Answer Published 12/02/2022 at 12:54 PM
The question is on the Mechanical Code. As such, section 401.2 states ventilation by natural means in accordance with Section 402 OR by mechanical means in accordance with Section 403 of the mechanical volume is required.
The Energy code comes into play with in this scenario when the mechanical ventilation section is where the air infiltration rate in the dwelling unit is less than 3 air changes.
The second question is regarding FBC-EC Sections C402.5.1 through C402.5.8. FBC-EC C402.5 provides methods to comply with building envelope tightness, method #1 is to comply with all requirements from Sections C402.5.1 through C402.5.8 and method #2 is to perform a blower door test. If complying with method #1 you must comply with C402.5.5 (Air intakes, exhaust openings, stairways and shafts). This section requires that air intakes and exhaust openings comply with C403.2.4.3.
Section C403.2.4.3 (Shutoff dampers) Requires dampers with automatic controls be installed in outdoor air intakes and exhaust openings and configured to close when the systems or space served is not in use or during unoccupied periods. Natural ventilation could be used if the openings to the outdoor are provided with dampers.
The Energy code comes into play with in this scenario when the mechanical ventilation section is where the air infiltration rate in the dwelling unit is less than 3 air changes.
The second question is regarding FBC-EC Sections C402.5.1 through C402.5.8. FBC-EC C402.5 provides methods to comply with building envelope tightness, method #1 is to comply with all requirements from Sections C402.5.1 through C402.5.8 and method #2 is to perform a blower door test. If complying with method #1 you must comply with C402.5.5 (Air intakes, exhaust openings, stairways and shafts). This section requires that air intakes and exhaust openings comply with C403.2.4.3.
Section C403.2.4.3 (Shutoff dampers) Requires dampers with automatic controls be installed in outdoor air intakes and exhaust openings and configured to close when the systems or space served is not in use or during unoccupied periods. Natural ventilation could be used if the openings to the outdoor are provided with dampers.
Commentary
None.