NABCEP Energy Efficiency & Conservation Techniques 4 — Questions and Answers
Question 1: Which lighting efficiency metric describes the amount of visible light produced per watt of electrical power consumed?
- Candela
- Lux
- Lumens per watt (efficacy) (Correct answer)
- Color Rendering Index (CRI)
Correct answer: Lumens per watt (efficacy)
Luminous efficacy (lumens per watt) is the standard measure of how efficiently a light source converts electrical energy into visible light.
Question 2: Earth tube (ground-coupled heat exchanger) systems pre-condition incoming ventilation air by:
- Using solar energy stored in roof panels
- Exchanging heat with the relatively stable ground temperature (Correct answer)
- Compressing air to raise its temperature before distribution
- Filtering air through activated carbon media
Correct answer: Exchanging heat with the relatively stable ground temperature
Buried tubes allow incoming air to exchange heat with stable ground temperatures (55–65°F), pre-warming air in winter and pre-cooling it in summer.
Question 3: A heat recovery ventilator (HRV) differs from an energy recovery ventilator (ERV) primarily because an HRV:
- Also transfers moisture between exhaust and supply air streams
- Transfers heat only without moving moisture (Correct answer)
- Uses a heat pump compressor to boost efficiency
- Only works in heating-dominated climates above 5,000 ft elevation
Correct answer: Transfers heat only without moving moisture
An HRV transfers sensible heat only, while an ERV additionally transfers latent energy (moisture), making ERVs better suited for humid climates.
Question 4: In the context of energy-efficient building design, what does 'thermal bridging' refer to?
- Connecting separate HVAC zones with shared ductwork
- A conductive path through insulation that bypasses its thermal resistance (Correct answer)
- Using thermal mass to bridge seasonal temperature differences
- Linking solar thermal collectors to a building's domestic hot water system
Correct answer: A conductive path through insulation that bypasses its thermal resistance
Thermal bridges are high-conductivity elements (like metal studs or concrete columns) that allow heat to bypass insulation, reducing overall envelope performance.
Question 5: Which metric is most appropriate for comparing annual energy costs of different heating fuel types?
- BTU content per unit of fuel
- Cost per million BTU (MMBtu) of useful heat delivered (Correct answer)
- Seasonal Energy Efficiency Ratio (SEER)
- Annual Fuel Utilization Efficiency (AFUE) alone
Correct answer: Cost per million BTU (MMBtu) of useful heat delivered
Cost per MMBtu of useful heat accounts for both fuel price and equipment efficiency, enabling a true apples-to-apples comparison across fuel types.
Question 6: Retrocommissioning (RCx) of an existing building is best described as:
- Demolishing and rebuilding the building to current energy codes
- Systematically investigating and correcting operational deficiencies to restore designed performance (Correct answer)
- Installing new high-efficiency equipment to replace all original systems
- Applying for ENERGY STAR certification for the first time
Correct answer: Systematically investigating and correcting operational deficiencies to restore designed performance
Retrocommissioning optimizes existing systems by identifying control faults, scheduling errors, and maintenance issues without major equipment replacement.
Question 7: Which measure would most effectively reduce baseload electricity consumption in a commercial building operating 24/7?
- Installing programmable thermostats with nighttime setback
- Replacing server room equipment with more efficient models and improving IT cooling (Correct answer)
- Adding exterior solar shading on south-facing windows
- Switching from natural gas to electric heat pumps for space heating
Correct answer: Replacing server room equipment with more efficient models and improving IT cooling
Server rooms and IT loads run continuously; improving equipment efficiency and precision cooling directly cuts 24/7 baseload consumption.
NABCEP Energy Efficiency & Conservation Techniques 4
Which lighting efficiency metric describes the amount of visible light produced per watt of electrical power consumed?