Building Energy Simulation (BES)

Whole building energy simulation is the use of computer-based tools to simulate the energy use of a building throughout an entire year of operation. In many cases, architects and building owners are inexperienced with energy modeling and don’t know how to harness this powerful tool to inform the design and decision-making process. Properly used, energy modeling can help optimize the building design and allow the design team to prioritize investment in the strategies that will have the greatest effect on the building’s energy use.

Building Energy Simulation is used to:

  • Predict energy consumption during future operation of the building
  • Optimize building design by selecting cost-effective solutions to reduce yearly operation costs
  • Help design team to make informed decisions regarding energy conservation measures implemented in the project
  • Demonstrate code compliance
  • Achieve points in LEED EA credit 1 “Optimize Energy Performance”


Energy modelling is a continuous process that gets more detailed, refined and accurate as the design process progresses.

• During the conceptual design of the project, energy modeling can extremely valuable input. A skilled energy modeler can quickly create a simplified model, with for example a single zone per major occupancy type. The decisions made early in the design have the greatest impact on the overall building energy consumption, such as: building form, orientation, massing, windows area and envelope characteristics. This kind of feedback is rarely available early in the design process, which is ironic since this is often where the biggest opportunities are.

• During schematic design, energy modeling allows those involved in the design process to optimize their focus on the most promising energy-saving strategies. Seeing how the energy consumption of a building breaks down by fuel type, task, and building component allows the design team to focus on the major drivers of energy use. As an example, imagine that the schematic design model shows the output in the figure below:




In this case study, space cooling and interior lighting represent together more than 50% of the overall building energy consumption. Therefore, energy efficiency measures should focus on these two categories. It would be wise to look at strategies that reduce cooling loads. We know that if cooling loads drop, then the energy needed for fans and pumps will also drop, because less energy is moved around the building. We also know that lighting energy has to be removed by the cooling system, so reducing lighting energy will also reduce cooling energy.

A logical next step is to look at the breakdown of the cooling load for the building. In this case study, the two largest components of the cooling load are solar gain through the windows and heat gain from lighting. Strategies to examine may include: window area per orientation, efficient lighting systems and controls, glazing with a lower solar heat gain coefficient, shading and so on.



• During design development, energy modeling permits parametric studies to be done. Specific energy-savings measures can be developed by varying one component (for example lighting power density, insulation thickness, glazing SHGC, HVAC equipment efficiency, control strategy, etc.) at a time in order to estimate its impact on the overall building energy consumption.

• During construction document phase, energy modelling allows comparison of the proposed design to the minimally code-compliant base-case building.



Building Energy Simulation Software

GreenBIM Engineering’s energy modelers use state of the art software in order to perform accurate Whole Building Energy Simulation and give valuable input to the project design team.The energy modeling team uses Autodesk’s Revit in order to create a simplified 3D model of the building based on the project’s architectural drawings. The Building Information Model (BIM) created includes information about the spaces, HVAC zones, building envelope, internal loads (people, lighting and equipment) and schedules of operation.

Through the Green Building XML (gbXML) open schema, the building properties stored in Revit’s 3D model is exported to an engineering analysis tool. Detailed Whole Building Energy Simulation is then performed on dedicated tools such as:

eQuest v3.65, with simulation engine derived from the latest version of DOE-2.
Trane Trace 700
Energy Plus


LEED and Building Energy Simulation

Energy performance is a critical element of integrated design for green buildings. The U.S. Green Building Council’s Leadership in Energy and Environmental Design Rating System (LEED™) requires energy modeling to assess the energy use of a building and to quantify the savings attributable to the proposed design.

All energy models performed by GreenBIM Engineering team have been validated by the Green Building Certification Institute (GBCI) reviewers.