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Duct Systems — ICC M1 Practice Questions

10 questions · 8% of the ICC M1 exam

Worked questions

1. 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.

2. A contractor is designing a duct system for a new residential building. The total length of the supply duct is 100 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.
  • 0.15 inches of water per 100 feet of duct.
  • C0.20 inches of water per 100 feet of duct.
  • D0.25 inches of water per 100 feet of duct.

Exam tip

Be familiar with the maximum allowable friction loss for different types of ducts.

Why B is correct

Section M1503.5 of the 2024 IRC states that the maximum allowable friction loss for supply ducts is 0.15 inches of water per 100 feet of duct.

3. A residential building is being constructed with a forced-air heating and cooling system. The contractor has installed a supply duct that runs through an unconditioned attic space. Which of the following is a requirement for the duct insulation according to the 2024 International Residential Code?

  • AInsulation must be R-3 for all ducts.
  • BInsulation must be R-6 for all ducts.
  • Insulation must be R-8 for supply ducts and R-3 for return ducts.
  • DInsulation must be R-13 for all ducts.

Exam tip

Remember the specific R-values required for duct insulation in unconditioned spaces.

Why C is correct

According to Section M1503.3.1 of the 2024 IRC, supply ducts in unconditioned spaces must have insulation with a minimum R-value of R-8, while return ducts must have a minimum R-value of R-3.

4. A residential building is being constructed with a forced-air heating and cooling system. The contractor is designing the duct system. According to the 2024 International Residential Code, what is the minimum size requirement for a supply duct serving a single bedroom?

  • 4 inches in diameter.
  • B5 inches in diameter.
  • C6 inches in diameter.
  • D8 inches in diameter.

Exam tip

Know the minimum size requirements for ducts serving different areas of a residential building.

Why A is correct

Section M1503.2 of the 2024 IRC specifies that a supply duct serving a single bedroom must be at least 4 inches in diameter.

5. During an inspection of an existing home, you notice that the ductwork is not properly sealed. What is the minimum requirement for ductwork sealing as per the 2024 International Residential Code?

  • Seal all joints and connections with mastic.
  • BSeal all joints and connections with tape.
  • CSeal all joints and connections with foil tape.
  • DSeal all joints and connections with weather stripping.

Exam tip

Mastic is the preferred method for sealing ductwork joints and connections.

Why A is correct

Section M1503.4 of the 2024 IRC specifies that all joints and connections in duct systems must be sealed with mastic to prevent air leakage.

6. During an inspection of an existing home, you notice that the ductwork is not supported at regular intervals. What is the minimum spacing requirement for duct supports according to the 2024 International Residential Code?

  • AEvery 4 feet.
  • BEvery 6 feet.
  • Every 8 feet.
  • DEvery 10 feet.

Exam tip

Supporting ductwork at the correct intervals is crucial for maintaining structural integrity.

Why C is correct

Section M1503.6 of the 2024 IRC requires that ductwork be supported at intervals not greater than 8 feet.

7. You are inspecting the ductwork in an existing home and notice that the airflow is significantly reduced. What is the first step in troubleshooting this issue?

  • ACheck the air filter.
  • Inspect the ductwork for leaks and obstructions.
  • CMeasure the airflow at the registers.
  • DReplace the furnace fan motor.

Exam tip

Always start with a visual inspection when troubleshooting airflow issues.

Why B is correct

The first step in troubleshooting reduced airflow is to inspect the ductwork for leaks and obstructions, as per the general principles of HVAC system maintenance.

8. You are inspecting the ductwork in an existing home and notice that the supply ducts are located in the living room ceiling. According to the 2024 International Residential Code, what is the minimum height requirement for supply ducts in the ceiling space?

  • A6 feet.
  • B7 feet.
  • 8 feet.
  • D9 feet.

Exam tip

Ensure that ductwork is installed at the correct height to avoid interference with ceiling fixtures.

Why C is correct

Section M1503.1 of the 2024 IRC requires that supply ducts in the ceiling space must be at least 8 feet above the finished floor.

2 more in the bank

Answers and explanations for these are in the app.

  • A residential building is being constructed with a forced-air heating and cooling system. During the inspection, you notice that the supply ducts are designed to deliver air at a velocity of 1500 fpm. What is the minimum diameter required for the supply ducts according to the 2024 International Residential Code?
  • You are inspecting the ductwork in an existing residential building and notice that the return ducts are located in the attic. How should you address the presence of insulation around the return ducts according to the 2024 International Residential Code?

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