The Fans screen allows the user to describe mechanical ventilation in the building.

Fan Name:

The unique name of the fan.

Ventilated Area

This box brings up the Assign Spaces to Fan window.

  • Assign Spaces to Fan window: Only conditioned (heated or/and cooled) spaces may be assigned to a fan. Each fan may serve multiple rooms. Each room may be assigned to not more than one fan.
    • Heated or Air Conditioned Spaces Not Served by any Fan area contains the list of spaces that are specified as conditioned but not yet assigned to a fan.
    • Heated or Air Conditioned Spaces Served by This Fan area contains the list of spaces that are already assigned to this fan, along with their floor area entered on the Spaces screen.

The total ventilated area in square feet is shown below the table. The area is updated each time a space is added or removed from the right panel.

Select a space in the left panel and click > to move it to the right and attach to the fan.

Click >> to attach all the spaces in the left panel to this fan.

Select a space in the right panel and click < to detach the space from this fan.

Click << to detach all spaces from this fan. You will not be allowed to close the window if no spaces are assigned to the fan (if the right panel is empty), because each fan must control at least one space.

Click OK to confirm your selection or Cancel to discard the inputs.

Use Delete button on the Fans screen to delete a fan. All spaces that were served by the deleted fan will be available for a new assignment.

Ventilation Rate CFM:

A CFM value may only be entered after the Ventilated Area box is filled in. Default value for this field is the CFM equivalent of 0.35 ACH for all rooms served by this fan. To edit the value click the gray area and the Ventilation Rate window will open.

  • Ventilation Rate window allows the user to specify ventilation rate in CFM or ACH. Click Convert to ACH (CFM) button any time during the input to convert between the two. The Ventilation Rate may be entered as total for the fan or on room-by-room basis. To Set Total Ventilation Rate select the appropriate radio button and enter the value. The total ventilation rate is distributed between the rooms that are served by the fan in proportion with the room volume.

Note: When you close the Ventilation Rate window and return to the Fans screen, the ventilation rate will display in CFM.

To Assign Ventilation to Each Space select the appropriate radio button and enter ventilation rate for each space manually.

The method described in ASHRAE Standard 136 may be used to superimpose exhaust and supply ventilation. Enter the resulting mechanical ventilation rate on the Fans screen.

Click OK to confirm the inputs or Cancel to discard.

Heat Recovery Efficiency %:

This value is only entered if a heat recovery ventilator is used. Enter 0 if there is no heat recovery.

Hours per Day Fan is On:

The average daily fan run time in hours. Your input on the Fans screen does not account for the electric load of fan motors. To model the electric load of the fan motors, the motors must be entered on the Appliances screen. The Appliance Library contains a few sample fan motor sizes with yearly electrical consumption based on usage assumptions given in the library. Verify that the usage assumptions in the library apply to your model, and adjust yearly electric consumption as necessary.