CEA Energy Modeling & Simulation Tools 3 — Questions and Answers
Question 1: Which DOE-2 simulation engine component handles the calculation of hourly heating and cooling loads?
- SYSTEMS
- LOADS (Correct answer)
- PLANT
- ECONOMICS
Correct answer: LOADS
The LOADS module in DOE-2 calculates space heating and cooling loads using the weighting factor method before passing results to the SYSTEMS module.
Question 2: In TRACE 700, what does the 'Design Day' cooling calculation determine?
- Annual energy consumption for cooling equipment
- Peak cooling load used to size coils and air handlers (Correct answer)
- Chiller part-load performance at average conditions
- Seasonal energy efficiency ratio (SEER) of cooling equipment
Correct answer: Peak cooling load used to size coils and air handlers
TRACE 700's Design Day cooling calculation finds the peak load under worst-case summer conditions to properly size HVAC components.
Question 3: What is the purpose of 'parametric analysis' in energy modeling software?
- To calibrate the model against measured consumption data
- To systematically vary input parameters and compare resulting energy impacts (Correct answer)
- To import weather data from multiple climate zones simultaneously
- To generate LEED energy credit documentation automatically
Correct answer: To systematically vary input parameters and compare resulting energy impacts
Parametric analysis runs multiple simulations with varied inputs (e.g., insulation levels, window types) to identify which measures have the greatest energy impact.
Question 4: In EnergyPlus, what object type is used to model a variable air volume (VAV) terminal unit?
- AirTerminal:SingleDuct:VAV:Reheat (Correct answer)
- ZoneHVAC:FourPipeFanCoil
- AirLoopHVAC:UnitarySystem
- Coil:Cooling:DX:SingleSpeed
Correct answer: AirTerminal:SingleDuct:VAV:Reheat
The AirTerminal:SingleDuct:VAV:Reheat object models a VAV box with reheat coil that varies airflow based on zone demand.
Question 5: Which metric best describes how closely a simulation model matches measured building energy use?
- Energy Use Intensity (EUI)
- Coefficient of Variation of Root Mean Square Error (CV-RMSE) (Correct answer)
- Source Energy Site Ratio
- Peak Demand Factor
Correct answer: Coefficient of Variation of Root Mean Square Error (CV-RMSE)
CV-RMSE normalizes the root mean square error by the mean measured value, providing a percentage-based accuracy metric for model calibration.
Question 6: In Revit + OpenStudio workflows, what is the primary function of the gbXML export?
- To export HVAC schedules to a building automation system
- To transfer building geometry and space data from Revit to energy analysis tools (Correct answer)
- To generate code compliance reports for local jurisdictions
- To synchronize material properties with cost estimating software
Correct answer: To transfer building geometry and space data from Revit to energy analysis tools
gbXML (Green Building XML) is an interoperability format that carries building geometry, space boundaries, and construction data from BIM tools to energy simulation engines.
Question 7: What is the 'balance point temperature' concept used for in building energy analysis?
- The outdoor temperature at which a building requires neither heating nor cooling (Correct answer)
- The setpoint at which HVAC switches between heating and cooling modes
- The temperature differential across insulation materials
- The peak design temperature for mechanical equipment sizing
Correct answer: The outdoor temperature at which a building requires neither heating nor cooling
The balance point temperature is the outdoor temperature at which internal and solar gains exactly offset heat losses, below which heating is needed and above which cooling may be required.
CEA Energy Modeling & Simulation Tools 3
Which DOE-2 simulation engine component handles the calculation of hourly heating and cooling loads?