CCP Building Envelope & Energy Audit 2 — Questions and Answers
Question 1: During a thermographic scan of a building envelope, which temperature differential between interior and exterior is generally considered the minimum for reliable results?
- 5°F (2.8°C)
- 10°F (5.6°C) (Correct answer)
- 20°F (11°C)
- 30°F (16.7°C)
Correct answer: 10°F (5.6°C)
A minimum 10°F (5.6°C) temperature differential is generally required for infrared thermography to reliably detect thermal anomalies in building envelopes.
Question 2: A blower door test on a commercial building reveals an air leakage rate of 0.40 CFM75/ft² of envelope area. How does this compare to ASHRAE 90.1 maximum allowances?
- It exceeds ASHRAE 90.1 limits (Correct answer)
- It meets ASHRAE 90.1 requirements exactly
- It is below the ASHRAE 90.1 maximum of 0.40 CFM25/ft²
- ASHRAE 90.1 does not specify envelope air leakage rates
Correct answer: It exceeds ASHRAE 90.1 limits
ASHRAE 90.1 requires commercial envelope air leakage no greater than 0.40 CFM75/ft² for continuous air barriers, so this reading is at or near the limit depending on exact test conditions.
Question 3: What is the primary purpose of a 'tracer gas' test in building envelope commissioning?
- Detecting combustion gas leaks from mechanical equipment
- Quantifying infiltration rates and identifying leakage pathways (Correct answer)
- Verifying HVAC duct tightness
- Measuring CO2 levels for IAQ compliance
Correct answer: Quantifying infiltration rates and identifying leakage pathways
Tracer gas tests inject a non-toxic gas (such as SF6 or CO2) and measure its decay to quantify air infiltration rates and locate leakage pathways in the building envelope.
Question 4: When conducting an energy audit for a facility with a large chiller plant, which metric is most useful for benchmarking chiller efficiency?
- EER (Energy Efficiency Ratio)
- kW/ton (Correct answer)
- SEER (Seasonal Energy Efficiency Ratio)
- COP at AHRI 550/590 standard conditions
Correct answer: kW/ton
kW/ton is the standard metric for benchmarking chiller plant efficiency, representing electrical input per ton of cooling produced, with lower values indicating better performance.
Question 5: In a Level II energy audit, a commissioning professional identifies that a roof assembly has a measured U-value of 0.065 Btu/h·ft²·°F. The design specified U-0.048. What is the most likely cause?
- Calculation error in the energy model
- Thermal bridging through metal fasteners or framing (Correct answer)
- Incorrect thermocouple placement during measurement
- The roof membrane UV degradation
Correct answer: Thermal bridging through metal fasteners or framing
Thermal bridging through metal fasteners, clips, or structural framing significantly increases effective U-value beyond the nominal insulation value, commonly explaining discrepancies between design and measured performance.
Question 6: Which ASTM standard governs the field measurement of air leakage through building envelopes using a calibrated fan pressurization method?
- ASTM E779 (Correct answer)
- ASTM E1186
- ASTM E283
- ASTM E2357
Correct answer: ASTM E779
ASTM E779 is the standard test method for determining air leakage rate by fan pressurization, widely used for commercial building envelope air tightness testing.
Question 7: A commissioning professional reviewing window specifications notes a center-of-glass U-factor of 0.25 but an assembly U-factor of 0.35. What accounts for this difference?
- Laboratory vs. field measurement variation
- Edge-of-glass and frame thermal bridging effects (Correct answer)
- Solar heat gain coefficient (SHGC) inclusion in assembly rating
- Condensation resistance factor adjustments
Correct answer: Edge-of-glass and frame thermal bridging effects
Assembly U-factor includes edge-of-glass conduction and frame thermal bridging effects, which are always higher than the center-of-glass value representing only the glazing itself.
CCP Building Envelope & Energy Audit 2
During a thermographic scan of a building envelope, which temperature differential between interior and exterior is generally considered the minimum for reliable results?