Rooftop unit capacity should not be selected from floor area alone.

A proper equipment selection should consider the actual building load and the operating conditions of the project.

What affects rooftop HVAC capacity?

• Project location and climate
• Indoor design temperature
• Building orientation
• Roof and wall construction
• Glass area and solar exposure
• Occupancy
• Lighting and equipment loads
• Fresh-air quantity
• Operating schedule
• Building use

Why is oversizing a rooftop unit a problem?

A significantly oversized unit can result in unnecessary cycling, poor part-load operation and potentially weaker humidity control.

A unit that is too small may be unable to maintain indoor design conditions during peak outdoor temperatures.

What should be calculated before equipment selection?

For project applications, the building load, required supply airflow, fresh-air load and duct external static pressure should be reviewed together.