Certified Energy Auditor Building Envelope and Lighting Questions and Answers — Questions and Answers
Question 1: An energy auditor inspects the attic of a home in a cold climate and observes dark, dirty-looking patches on the fiberglass batt insulation directly above the interior ceiling joists. What is the most likely cause of this phenomenon?
- Radiant heat transfer discoloring the insulation.
- Air leakage through ceiling penetrations carrying dust and moisture, which is then filtered by the insulation. (Correct answer)
- Compression of the insulation, reducing its R-value and causing dust to settle differently.
- Natural degradation of the insulation material due to age.
Correct answer: Air leakage through ceiling penetrations carrying dust and moisture, which is then filtered by the insulation.
These dark patches are a classic sign of air leakage, also known as 'ghosting' or 'filtration soiling.' Warm, moist, and often dusty air from the conditioned space below leaks into the colder attic through gaps and cracks. The insulation acts as a filter, trapping the dust particles and creating the darkened appearance. This indicates a need for air sealing to reduce energy loss.
Question 2: Which of the following window performance metrics is most crucial for an energy auditor to consider when trying to reduce cooling loads in a hot, sunny climate?
- High Visible Transmittance (VT)
- Low U-factor
- A high Condensation Resistance (CR) rating
- Low Solar Heat Gain Coefficient (SHGC) (Correct answer)
Correct answer: Low Solar Heat Gain Coefficient (SHGC)
The Solar Heat Gain Coefficient (SHGC) measures how much heat from direct sunlight is transmitted through a window. A lower SHGC value means less solar heat is admitted, which is critical for reducing the building's cooling load and associated energy costs in a climate dominated by sun and heat. While a low U-factor is also important for reducing conductive heat transfer, SHGC directly addresses the impact of solar radiation.
Question 3: A lighting retrofit project involves replacing 400-watt metal halide lamps in a warehouse with 150-watt LED fixtures. Which metric best describes the energy efficiency of these light sources in terms of light output per unit of power consumed?
- Luminous Efficacy (lumens/watt) (Correct answer)
- Color Rendering Index (CRI)
- Correlated Color Temperature (CCT)
- Luminous Flux (lumens)
Correct answer: Luminous Efficacy (lumens/watt)
Luminous Efficacy is the standard metric for lighting efficiency. It is calculated by dividing the total light output in lumens by the total power input in watts (lumens/watt). A higher luminous efficacy value indicates a more efficient light source, as it produces more light for each watt of energy consumed.
Question 4: An energy audit of a commercial office building reveals that the perimeter offices, which have large windows, have their lights on at full brightness even on sunny days. Which lighting control strategy would provide the greatest energy savings for this specific situation?
- Ultrasonic occupancy sensors
- Astronomical time clocks
- Daylight harvesting with photosensors (Correct answer)
- Manual dimmers for each office
Correct answer: Daylight harvesting with photosensors
Daylight harvesting is a control strategy that uses photosensors to measure the amount of ambient natural light entering a space. When sufficient daylight is present, the control system automatically dims or turns off the electric lights, thereby saving energy. This is the most direct and effective solution for the scenario described.
Question 5: When calculating the overall heat transfer of a wall assembly, an auditor must account for the wood or metal studs that interrupt the insulation. This phenomenon, where heat flows more readily through the framing members than through the insulated cavities, is known as:
- Convective looping
- Thermal bridging (Correct answer)
- Air stratification
- Radiant coupling
Correct answer: Thermal bridging
Thermal bridging occurs when a more conductive material (like a wood or steel stud) creates a path of lower thermal resistance, allowing heat to bypass the insulation. This reduces the overall effective R-value of the assembly and must be accounted for in accurate heat loss or gain calculations. It is a significant factor in a building's thermal performance.
Question 6: What is the primary function of a low-emissivity (Low-E) coating on a window pane in a heating-dominated climate?
- To block the transmission of visible light to reduce glare.
- To increase the solar heat gain during winter months.
- To reflect long-wave infrared heat back into the conditioned space, reducing heat loss. (Correct answer)
- To increase the structural integrity of the insulated glass unit (IGU).
Correct answer: To reflect long-wave infrared heat back into the conditioned space, reducing heat loss.
Low-E coatings are microscopically thin, transparent layers of metal or metallic oxide applied to a window surface. Their primary function is to reduce heat transfer by reflecting infrared radiation (heat). In a cold, heating-dominated climate, the coating is typically applied to an interior surface of the glass unit to reflect long-wave infrared heat from furnaces and occupants back into the room, thus reducing winter heat loss.
