Building Systems & Energy Efficiency Flashcards
7 cards from real CEA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Building Systems & Energy Efficiency flashcards as text
A boiler operates at 78% thermal efficiency. If the boiler input is 1,000 MBH, what is the useful heat output?
Answer: 780 MBH
Useful output = input × efficiency = 1,000 MBH × 0.78 = 780 MBH; the remaining 220 MBH is lost through flue gases and jacket losses.
What does ASHRAE 90.1 primarily regulate for commercial buildings?
Answer: Energy efficiency design requirements for building envelope, HVAC, lighting, and service water heating
ASHRAE 90.1 is the Energy Standard for Buildings Except Low-Rise Residential Buildings, setting minimum efficiency requirements for envelope, HVAC, lighting, and SWH systems.
Which control strategy directly reduces plug load energy consumption in an office?
Answer: Occupancy-based power strip switching
Occupancy-based smart power strips cut power to workstation peripherals when a workstation is unoccupied, directly targeting plug and process loads.
In a heat recovery ventilation (HRV) system, what is the function of the heat exchanger core?
Answer: Transfer heat between exhaust and supply air streams without mixing them
The HRV core transfers sensible heat (and in ERV systems, moisture) from the warmer exhaust stream to the cooler supply stream, recovering energy that would otherwise be wasted.
What is the 'stack effect' in tall buildings and how does it affect energy use?
Answer: Warm air rises creating pressure differentials that drive infiltration and increase heating/cooling loads
Stack effect creates a buoyancy-driven pressure difference that forces warm air out at upper floors and draws cold outdoor air in at lower floors, significantly increasing heating energy in winter.
A facility manager wants to benchmark energy performance against similar buildings. Which tool should they use?
Answer: ENERGY STAR Portfolio Manager
ENERGY STAR Portfolio Manager is the EPA's free online tool for tracking and benchmarking energy and water consumption relative to similar buildings nationwide.
In demand-controlled ventilation (DCV), CO₂ sensors are used to:
Answer: Modulate outdoor air intake based on actual occupancy levels
DCV uses CO₂ as a surrogate for occupancy; when CO₂ rises above setpoint, outdoor airflow increases, saving fan and conditioning energy during low-occupancy periods.