Air Balancing

The Air Balancing pane is where you balance each space’s airflows. It sits between Configuration and Duct Layout in the System Design section.

Configuration works on central units and terminal units. Air Balancing works on spaces only, so it has no tab switcher and no diagram view — the sidebar lists every space in the project, and the pane always shows the floor plan. Pick the equipment mode in the selector at the top left of the plan before you edit, because design airflows are stored per mode.

Spaces come from the Building Model. Until the project has one, the sidebar shows No Spaces with a Create Spaces button that opens the Spaces pane.

Space Airflows

Select a space to balance its airflows in the Space Data panel. The Required column shows the calculator’s minimum. Most of the Design column is editable, and each edited cell resets back to its calculated value:

• Supply - Conditioned air the unit delivers to the space; defaults to the largest of the load-driven, code-driven (ACH/area), and ventilation requirements on a coupled terminal. A decoupled terminal takes its outdoor air directly, so ventilation does not raise its supply
• Return - Air drawn back from the space to be reconditioned
• Exhaust - Air discharged outdoors, driven by the space type’s exhaust requirement
• OA (VRP, Mixed) / OA (VRP, Direct) - Outdoor air required by the ASHRAE 62.1 Ventilation Rate Procedure. The label reads Mixed when outdoor air is blended into the supply at the unit, or Direct when a dedicated outdoor-air system (DOAS) delivers it straight to the space. Only Direct is editable; Mixed is calculated, and you raise it through the Supply row instead
• OA (IAQP, Mixed) / OA (IAQP, Direct) - Outdoor air from the ASHRAE 62.1 Indoor Air Quality Procedure, after crediting in-space air cleaning. This row appears only when the space has an IAQP result, and it is always read-only
• Transfer In and Transfer Out - Air moved to or from adjacent spaces
• Differential - Net balance: supply plus transfer in, minus return, exhaust, and transfer out. For a decoupled terminal, direct outside air also counts toward the plus side. A positive value pressurizes the space. This row is always calculated

HVAKR warns when a space is out of balance, and names the amount: adjust return, exhaust, or transfer air until supply (plus direct outside air, for a decoupled terminal) matches the air leaving the space.

Where the Supply Default Comes From

Below the table, Space Data reports the values the Supply default is built from. All of them are read-only:

• Area and Occupancy - The space’s floor area and design occupancy
• Total Space Sensible - The space’s sensible load
• Sensible from Direct OA - The share of that load carried by direct outdoor air. Shown for a decoupled terminal only
• Load-determined Supply - Airflow needed to carry the sensible load at the unit’s supply air temperature
• Required Minimum Supply - The code-driven minimum from the space type’s ACH and per-area rates

When the space has an IAQP result, the sidebar adds IAQP Air Cleaners, IAQP Air Cleaning (Vc), IAQP Outdoor Air, and IAQP Controlling Requirement. The controlling requirement names the individual compound or mixture that sets the minimum IAQP airflow. IAQP Outdoor Air reads Not achievable or Not evaluable when the procedure cannot produce a rate. An air cleaner with no linked product contributes nothing, and HVAKR says so.

Airflow Diagram and Psych Chart

Each selected space shows an airflow diagram above its data: supply entering on the left, return and exhaust leaving on the right, and the differential below. For a decoupled terminal, direct outside air also enters on the left.

Click the chart button (Open the airflow diagram and psych chart) in the panel header to open a larger dialog with the diagram and a psychrometric chart side by side. The chart plots the space type’s indoor setpoint against the supply air the serving equipment delivers, with the same comfort zones and Space SHR line the Configuration chart uses.