A contractor is designing a duct system for a new residential building. The total length of the return duct is 75 feet. According to the 2024 International Residential Code, what is the maximum allowable friction loss for this duct?
- A0.10 inches of water per 100 feet of duct.
- B0.12 inches of water per 100 feet of duct.
- 0.15 inches of water per 100 feet of duct.
- D0.18 inches of water per 100 feet of duct.
Exam tip
Be familiar with the maximum allowable friction loss for different types of ducts.
Why C is correct
Section M1503.5 of the 2024 IRC states that the maximum allowable friction loss for return ducts is 0.15 inches of water per 100 feet of duct.