Building Systems & Energy Efficiency Flashcards

Which type of lighting control provides the greatest energy savings in private offices?

Answer: Daylight harvesting with continuous dimming

Daylight harvesting with continuous dimming reduces electric light output in proportion to available daylight, providing savings throughout occupied hours rather than only when spaces are unoccupied.

A chilled water system is being converted from a constant-flow to a variable primary flow system. The primary benefit is:

Answer: Reduced pump energy through variable speed operation

Variable primary flow eliminates the need for a primary/secondary decoupler and allows pump speeds to vary with load, drastically reducing pump energy via the affinity cube law.

What is the Solar Heat Gain Coefficient (SHGC) of a window?

Answer: The fraction of incident solar radiation transmitted through the window as heat

SHGC represents the fraction of incident solar energy (both direct transmission and absorbed/re-emitted) that enters the building as heat; lower SHGC reduces cooling loads.

An energy audit reveals that a compressed air system has a leak rate of 25%. What is the best first step to reduce this waste?

Answer: Conduct a leak detection survey and repair leaks

Leak detection (using ultrasonic detectors or soap solution) and prompt repair is the highest-priority, lowest-cost measure for compressed air systems, typically with paybacks under one year.

In energy modeling, what is the purpose of a 'baseline' building model under ASHRAE 90.1 Appendix G?

Answer: To establish a code-compliant reference against which proposed design savings are measured

The Appendix G baseline model represents a code-minimum building and is used to calculate the percentage energy cost savings of the proposed design for programs like LEED.

Which heat pump type is generally most efficient in climates with ground temperatures between 45–75°F year-round?

Answer: Ground-source (geothermal) heat pump

Ground-source heat pumps exchange heat with stable ground temperatures, avoiding the efficiency penalties of air-source systems during extreme outdoor temperatures.

A roof membrane with a solar reflectance of 0.75 and thermal emittance of 0.90 is classified as a 'cool roof.' This primarily reduces:

Answer: Cooling loads by reducing solar heat absorbed by the roof surface

High solar reflectance rejects most incident solar radiation before it converts to heat, reducing roof surface temperatures and the conductive heat flux into the building below.