Bath Vent Codes
- 1 cfm per square foot. Not. 
- Seed Eco-Home Floor 1 has a 5x9 bathroom = 45 sf.
- Not! The code requirement is a minimum of 20 cfm continuous, or 50 cfm intermittent. IRC - [M1507.4] - 
- Continuous means running 24/7
- Code does not stipulate bathroom size.
- Ducts are very specific - 3" smooth for 50 CFM is required, 3" flex is not allowed at 50 CFM Table M1506.2  - but 4" flex is allowed
- Section M1507.2  covers local exhaust fans, including bathroom. It stipulates only exhaust rates, not vent material.
- Does vent material matter?
- Bathrooms with bath facilities require minimum of 80 CFM here . It states pursuant to table M1507.3, which is not found in IRC 2020 or IRC 2016. Must be an older code? Yes, 2011 code, so it's outdated.
- Bathroom exhaust has been updated to 50 CFM minimum in 2016 and 2020 IRC editions.
- Note video shows 3" flex duct - appears to be not to code - https://youtu.be/hckMnenDU4s?t=503