Building Pressure: The Invisible Force Affecting Every Commercial Building

If a building's doors are hard to open, slam shut, won't close properly, or occupants complain of drafts and humidity, building pressure is often the cause.

Building pressure is the difference between indoor and outdoor air pressure. It's invisible, constantly changing, and has a major impact on comfort, energy efficiency, indoor air quality, and moisture control.

What Creates Building Pressure?

Three forces determine a building's pressure:

• Stack Effect – Warm air rises and escapes through the upper portions of a building, pulling outside air in at lower levels.

• Wind – Wind creates constantly changing pressure around the building envelope.

• HVAC System – The balance between outdoor air, supply air, return air, and exhaust air is the one factor that can be controlled.

Most commercial buildings are designed to operate at slightly positive pressure, allowing conditioned air to leak outward instead of drawing hot, humid, or contaminated outdoor air inside.

Common Signs of a Pressure Problem

• Doors are difficult to open or slam shut

• Doors won't fully close or stand open

• Drafts near entrances or windows

• Uneven temperatures throughout the building

• High indoor humidity or moisture issues

• Filters loading faster than expected

• Higher-than-normal energy costs

Negative pressure can also create indoor air quality concerns by allowing combustion gases or other contaminants to enter occupied spaces.

Why It Matters

Improper building pressure often leads to occupant complaints, moisture damage, increased operating costs, and unnecessary warranty callbacks.

For engineers, proper pressure verifies the design is performing as intended.

For general contractors, it reduces post-construction issues and helps deliver a building that performs correctly from day one.

For building owners, it improves comfort, protects the building envelope, and lowers long-term operating costs.

How It's Verified

Building pressure can't be confirmed by design drawings or damper positions alone—it must be measured.

A Testing, Adjusting, and Balancing (TAB) contractor verifies airflow, adjusts fan speeds and dampers, confirms pressure sensor accuracy, and ensures the HVAC system is maintaining the proper building pressure under real operating conditions.

The Bottom Line

A building may be designed for proper pressure, but only testing can confirm it's actually operating that way. Proper TAB helps ensure a building is comfortable, energy efficient, and performing as intended.