Certified Energy Auditor Certification Building Envelope and Lighting 4 — Questions and Answers
Question 1: Which factor most significantly reduces the effective R-value of a fiberglass batt insulation in a stud wall assembly?
- Moisture absorption by the batt
- Thermal bridging through wood studs (Correct answer)
- Convective loops within the batt material
- Radiant heat transfer across the stud cavity
Correct answer: Thermal bridging through wood studs
Wood studs have a much lower R-value than cavity insulation, and thermal bridging through studs typically reduces a wall's effective R-value by 15-25% compared to the cavity R-value alone.
Question 2: An energy auditor finds that a facility's T8 fluorescent lamps operate at 3,000 hours per year and consume 32W each. If replaced with 18W LED tubes producing equal lumens, what is the annual kWh savings per lamp?
- 21 kWh
- 42 kWh (Correct answer)
- 54 kWh
- 96 kWh
Correct answer: 42 kWh
Power reduction = 32W - 18W = 14W; annual savings = 14W × 3,000 hrs ÷ 1,000 = 42 kWh per lamp per year.
Question 3: What is the primary function of a low-emissivity (low-e) coating on window glass?
- Reduce visible light transmission to improve comfort
- Reflect long-wave infrared radiation to reduce radiant heat transfer (Correct answer)
- Absorb solar radiation to slow conductive heat transfer
- Block ultraviolet radiation to protect interior furnishings only
Correct answer: Reflect long-wave infrared radiation to reduce radiant heat transfer
Low-e coatings reflect long-wave infrared radiation, significantly reducing radiant heat transfer between the glazing surface and building interior, improving window U-factor.
Question 4: A daylight harvesting control system dims electric lights in response to:
- Time-of-day schedules
- Occupancy sensor signals
- Available natural daylight measured by a photosensor (Correct answer)
- Utility demand response signals
Correct answer: Available natural daylight measured by a photosensor
Daylight harvesting systems use photosensors to measure ambient light levels and automatically dim electric lighting to maintain target illuminance while maximizing use of natural daylight.
Question 5: What does the fenestration-to-wall ratio (FWR) describe in building energy analysis?
- The ratio of operable windows to fixed windows in a façade
- The percentage of gross exterior wall area that is glazed (Correct answer)
- The ratio of window height to wall height
- The proportion of south-facing to north-facing windows
Correct answer: The percentage of gross exterior wall area that is glazed
Fenestration-to-wall ratio (FWR) is the ratio of total glazed area to gross above-grade exterior wall area, a key metric in energy codes that limits heat gain/loss through windows.
Question 6: Which infiltration measurement technique uses tracer gas to determine building air change rates under natural conditions?
- Blower door depressurization test
- Duct blaster pressurization test
- CO2 tracer gas decay method (Correct answer)
- Thermographic infrared scanning
Correct answer: CO2 tracer gas decay method
The tracer gas decay method introduces a measured amount of tracer gas (such as CO2 or SF6) and monitors its concentration decay over time to calculate natural air change rates.
Question 7: In lighting retrofit analysis, simple payback period is calculated as:
- Annual energy savings divided by installed cost
- Installed cost divided by annual energy cost savings (Correct answer)
- Installed cost multiplied by annual operating hours
- Annual kWh savings divided by utility rate
Correct answer: Installed cost divided by annual energy cost savings
Simple payback period = installed cost ÷ annual energy cost savings, expressing how many years it takes for energy savings to recover the initial investment.
Certified Energy Auditor Certification Building Envelope and Lighting 4
Which factor most significantly reduces the effective R-value of a fiberglass batt insulation in a stud wall assembly?