Testing Large Buildings: Multi-Fan Airtightness Testing of a Factory

A Project Case Study: 11 Networked Fans, One Control Software

Introduction

Testing a house with a single blower door fan is routine. Testing a factory is a different problem. Industrial buildings have huge air volumes, tall roofs, large roller shutters, and long stretches of envelope. One fan simply cannot move enough air to bring a building this size to test pressure.

In this article we share how SANA Engineering handled this on a recent project: a large factory tested with 11 calibrated fans, networked together and controlled from a single software interface.

1. Why Large Buildings Are Different

The principle is the same: pressurize or depressurize the building and measure the airflow needed to hold the pressure. What changes is how hard it is to do this properly.

• Air volume: A big, leaky building needs far more airflow than one fan can deliver.

• Pressure uniformity: In a large open hall, one fan at one door can leave the far side at a different pressure, making the result less meaningful.

• Wind and stack effect: Large wall and roof areas are more exposed, so baseline pressures move more.

• Many openings: Roller doors, dock doors, louvers, and exhaust fans must all be identified and sealed or accounted for.

The answer is to spread the airflow around the building and make several fans work as one system.

2. The Project and the Solution

The client operated a large factory with a very large production hall. The airtightness test was one of the requirements for the project to meet LEED certification, so the client needed a measured value for the envelope, not a design assumption, and wanted to know where the main leaks were. Our planning showed that about 11 fans were needed to test the whole building in one go, as one zone.

We installed the fans in openings around the building, using adjustable frames and fabric panels to seal each one. Spreading them out kept the internal pressure as uniform as possible. All 11 fans were then connected in a network and operated from one computer through the test software. The operator sets one target pressure and the software coordinates the fans:

• One control point: A single operator runs the entire system.

• Synchronized fan speeds: The fans ramp up together and hold the target pressure steadily.

• Combined airflow: The software adds the flow from every fan to give total building leakage, with live monitoring of pressure and flow.

3. How We Ran the Test Multi-fan airtightness testing

We followed our usual methodology, in line with ASTM E779, ASTM E1827, and ISO 9972, adapted for a multi-fan setup.

Step 1: Plan and prepare

We defined the test Multi-fan airtightness testing

boundary, located the openings, and planned the fan layout. HVAC was switched off, intentional openings were sealed, and loose items were secured.

Step 2: Install and network the fans

The 11 fans were mounted, sealed, and connected to the control software. Every fan was checked, and the baseline pressure was recorded.

Step 3: Run the multi-point test

The target test pressure was 75 Pa, higher than the usual 50 Pa reference, which the large fan array made possible. The software stepped the building up to 75 Pa while the fans held each pressure steady, giving a reliable leakage curve instead of a single reading.

Step 4: Analyze, find leaks, and report

Results were converted to standard metrics such as air changes per hour (ACH) and air permeability per square meter of envelope, reported at 75 Pa and, where needed, at the 50 Pa reference. We then used an AirTracer smoke generator to see exactly where air was leaking, and the leaks we found were treated and repaired.

4. Challenges and Results

• Fan coordination: Eleven fans must act as one. Networked control made this practical.

• Wind and site conditions: We timed the test around calm weather, kept work areas clear, and secured dust and loose materials before pressurizing.

The client received a measured airtightness value for the whole building, visual smoke evidence of the leaks and their repair, prioritized recommendations, and a baseline to compare against after repairs, with test data that supports the project’s LEED documentation.

5. Why Work with SANA Engineering Co.

• Hands-on experience with multi-fan testing on large and complex buildings

• Professional, calibrated Retrotec equipment and networked control software

• Testing to recognized international standards, with clear, prioritized reports

Contact SANA Engineering Co. to discuss airtightness testing for your large building or industrial project.