HERS - Certified Home Energy Rating System Rater Blower Door & Duct Testing Questions and Answers 1 — Questions and Answers
Question 1: A HERS Rater is performing a blower door test on a 2,500 sq ft house with 8-foot ceilings. The final reading on the manometer is 1,800 CFM50. What is the approximate Air Changes per Hour at 50 Pascals (ACH50)?
- 4.82 ACH50
- 5.40 ACH50 (Correct answer)
- 6.00 ACH50
- 7.20 ACH50
Correct answer: 5.40 ACH50
To calculate ACH50, use the formula: (CFM50 * 60) / Conditioned Volume. First, find the volume: 2,500 sq ft * 8 ft = 20,000 cubic feet. Then, apply the formula: (1,800 CFM50 * 60) / 20,000 cu ft = 108,000 / 20,000 = 5.4 ACH50.
Question 2: According to ANSI/RESNET/ICC 380, what is the standard pressure difference that must be induced across the building envelope for a single-point blower door test?
- 25 Pascals
- 75 Pascals
- 50 Pascals (Correct answer)
- 100 Pascals
Correct answer: 50 Pascals
The ANSI/RESNET/ICC 380 standard specifies that blower door tests for measuring building envelope airtightness are conducted at a pressure difference of 50 Pascals (Pa) with respect to the outdoors.
Question 3: When performing a duct leakage to outside test, what is the primary function of the blower door?
- To pressurize the duct system to 50 Pa while the duct tester measures leakage.
- To create a neutral pressure plane between the house and the outdoors.
- To pressurize or depressurize the house to the same pressure as the duct system (typically 25 Pa). (Correct answer)
- To measure the total building envelope leakage simultaneously with the duct leakage.
Correct answer: To pressurize or depressurize the house to the same pressure as the duct system (typically 25 Pa).
In a duct leakage to outside test, the blower door is used to pressurize (or depressurize) the house to the same pressure as the duct system, which is typically 25 Pa. This equal pressure neutralizes any leakage between the ducts and the conditioned space, so the duct tester only measures air leaking to the outside of the conditioned envelope.
Question 4: A HERS Rater is preparing a home for a blower door test according to RESNET standards. Which of the following should be done to prepare the house?
- Seal all HVAC supply and return registers with tape.
- Close and latch exterior windows and doors, but do not apply extra sealing. (Correct answer)
- Turn off the water heater and seal its flue vent.
- Close all interior doors to isolate each room.
Correct answer: Close and latch exterior windows and doors, but do not apply extra sealing.
Per ANSI/RESNET/ICC 380, exterior windows and doors should be closed and latched as they would be normally, without extra sealing beyond the standard weatherstripping. Interior doors must be opened, HVAC systems turned off, and dampers must be closed but not sealed.
Question 5: Which of the following scenarios describes a 'Total Duct Leakage' test?
- A test using both a blower door and a duct tester to measure leaks to the attic and crawlspace.
- A test performed at the rough-in stage before drywall is installed.
- A test that measures all the air leaking from the duct system, regardless of whether it leaks into conditioned or unconditioned space. (Correct answer)
- A test where the duct system is pressurized to 50 Pa and compared against the building's CFM50 value.
Correct answer: A test that measures all the air leaking from the duct system, regardless of whether it leaks into conditioned or unconditioned space.
A 'Total Duct Leakage' test measures all the air escaping from the duct system, including leaks to the inside of the conditioned space and leaks to the outside (e.g., attics, crawlspaces). This is distinct from a 'Leakage to Outside' test, which isolates only the leaks to unconditioned areas.
Question 6: When performing a duct leakage test in accordance with ANSI/RESNET/ICC 380, the duct system is typically pressurized or depressurized to what pressure differential relative to the surrounding space?
- 50 Pa
- 75 Pa
- 10 Pa
- 25 Pa (Correct answer)
Correct answer: 25 Pa
The standard test pressure for both total duct leakage and leakage to the outdoors, as specified by RESNET standards, is 25 Pascals (0.10 inches water column).
HERS - Certified Home Energy Rating System Rater Blower Door & Duct Testing Questions and Answers 1
A HERS Rater is performing a blower door test on a 2,500 sq ft house with 8-foot ceilings.
The final reading on the manometer is 1,800 CFM50.
What is the approximate Air Changes per Hour at 50 Pascals (ACH50)?