Capturing Required Airflow Values from a Heating and Cooling Loads Report

The Simple version of the Heating and Cooling Loads Report displays many values that are useful for designing HVAC systems. These are reported for:

  • the entire building
  • each Zone in the building
  • each Space within each Zone

The values that we’ll focus on are:

  • Peak Cooling Airflow (CFM)
  • Peak Heating Airflow (CFM)

Which Value to Use

The two values describe the same duct and diffusers at two different times of year. Peak Cooling Airflow is what the space needs on the summer design day, and Peak Heating Airflow is what it needs on the winter design day. The system never delivers both at once.

  • Specified Supply Airflow = max(Peak Cooling Airflow, Peak Heating Airflow)
  • Cooling usually governs. Cooling requirements are typically higher than heating in most cases, so expect cooling to govern in most spaces.
  • Ventilation sets a floor. If the maximum comes out below the space’s required outdoor air or a minimum air change rate, use the higher value instead.
  • Caveat for VAV systems:
    • VAV systems need more than one number.
      • Specified Supply Airflow holds a single value, which works as the box’s maximum (cooling) airflow.
      • The minimum (heating) airflows are specifed on the VAV box or air terminal parameters, not on the space.

Workflow

Copy the Specified Supply Airflow to Each MEP Space

The Heating and Cooling Loads tool runs on the energy analytical model. It writes results to the analytical spaces, the system zones and the Loads Report, not back to your MEP spaces.

To work around this limitation, you must copy the results back to your Space Schedule.

  • Read the CFM by zone or space from the Loads Report.
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    1. In this example, you’d use:
      • Space 3: 2,694 CFM
      • Space 4: 3,208 CFM
  • Open your Space Schedule.
    • If needed, add the field Specified Supply Airflow to the list of columns to display.
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  • Copy the values for each Space from the Loads Report to the Specified Supply Airflow cell.
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AI Prompts

You can use AI tools to copy the values for each Space from the Loads Report to the corresponding Specified Supply Airflow cell.

  • First, right-click on the Loads Report and choose Save As.
    • Save the report as a file of type Webpage, complete.
  • Copy the file created and paste it the AI chatbot’s prompt.
  • Enter this prompt.
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Copying Airflow Values