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 A calibrated energy model should play a central role in building out a decarbonization plan because it provides insights on:

  • Current building energy and carbon profiles, and costs
  • Potential energy, carbon and cost savings of energy conservation measures (ECMs)
  • The impact of groups of ECMs, and the order in which they should be implemented over time.

The steps to follow include:

  • An initial energy model is developed using commonly available building information such as architectural floorplans, MEP schedule sheets, and BMS sequences of operation. 
  • The initial model is then refined and “calibrated” to the building’s real utility data for each utility consumed, creating a baseline condition that ECM’s will be compared against. 
  • The baseline energy model is used as a test bed for individual ECMs to understand potential energy, carbon and cost impacts. 
  • Evaluate the financial performance of each ECM. These results will be used to identify strategies that are economically viable and should be considered further.  
  • Those ECMs that are economically viable on their own may be grouped together with other ECMs to help build a holistic business case for system optimization and maximum carbon reduction. 
  • During the evaluation process, the project team should take the evolving emission factors associated with utilities such as electricity and steam, as well as the impact of rising average and design day temperatures/humidity, into account.

Key outputs from the energy modeling workflow should include data driven charts showing energy end use breakdown and costs, carbon footprint of each utility, building carbon emissions vs. LL97 targets and fines, and who "owns" the carbon footprint (i.e. tenants, building operations). It is important to note that not all energy models are created equal. For a deep energy retrofit project, the accuracy of the energy model should align with ANSI/ASHRAE/IES Standard 90.1. Code or LEED energy models that were developed for the building in the past are not appropriate for this effort.  

You can learn more about building energy modeling here.

Below is a selection of the energy modeling software packages used to support the case study findings presented in this Playbook, and throughout the industry. 

eQuest DesignBuilder DOE-2 EnergyPlus OpenStudio


Build and Calibrate the Initial Energy Model

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An energy model is developed in multiple phases. In the first phase, the energy modeler must build an initial model that captures the geometry, material attributes, occupancy types, MEP systems and basic information about the building’s operations. The energy modeler should also include surrounding buildings that may impact sun exposure on the different facades of the building under study. This initial model will produce a rough estimate of how the building performs every hour during the year. Then in the next phase, the energy modeler must hone the model’s accuracy by “calibrating” the initial model to measured utility data and detailed building operations information. Code or LEED energy models that may have been created for the building during its initial design and construction should not be used in deep energy retrofit study efforts because they do not reflect the actual performance of the building under study. 


Inputs for this task include the well-organized compilation of information and data collected during the Discovery Phase. Refer to the “Learn the Building” section for specific information of what should be collected.


Define and Understand the Purpose of the Energy Model

The purpose of energy modeling in this context is to provide high-accuracy estimates of potential energy, cost and carbon savings for energy conservation measures (ECMs) under consideration. The energy model should incorporate site weather data for a typical year as well as detailed information about building geometry, building construction, systems, operations, and occupancy. The energy model will use this information to simulate the building’s energy consumption for every hour of the year.  

Code or LEED energy models that may have been created for the building during its initial design and construction should not be used in deep energy retrofit study efforts because they do not reflect the actual performance of the building under study. 

The goal at this phase of the project is not to create an exact replica of the building—doing so would require modeling effort and investment in building metering that does not yield improvements in model accuracy that will improve decision making. Instead, energy models routinely include simplifications that maintain fidelity to metered data and an appropriate level of detail to form a basis of comparison for ECMs under consideration.

Create the Initial Energy Model   

The initial energy model should reflect the basic components of the building including geometry, HVAC systems, occupancy, and basic building operations. The initial model will generate an energy profile for the building that can be compared to measured utility data for calibration purposes.

Vornado Energy Model Image 1Vornado Energy Model Image 2