Estimate the Fan Configuration or Number of Fans Needed for Your Blower Door Test

When planning a blower door test for a large commercial or multi-unit building, knowing exactly how many fans you’ll need isn’t guesswork — it’s simple math.
At BEO Buildingscience, we take the uncertainty out of airtightness testing. Whether you’re working on a Green Star, Passive House, or compliance project, our engineers use precise airflow modelling to determine the optimal number of fans for your building’s size, pressure target, and leakage characteristics.

What Is a Blower Door Fan Calculation?

A blower door fan calculation determines the total airflow required to pressurise (or depressurise) a building during an airtightness test.
In simple terms, it tells you how many fans you’ll need to reach your target pressure — typically 50 Pa — without overloading or under-pressurising your system.

Understanding the Role of Fan Capacity in Airtightness Testing

Each fan model has a specific capacity, and larger buildings can require multiple fans to reach the desired test pressure. Knowing this in advance helps you plan logistics, avoid costly retesting, and meet your certification targets efficiently.

Why Accurate Fan Estimation Matters

Underestimating airflow can mean the test stalls before it reaches 50 Pa; overestimating wastes time, energy, and money.
Our team uses Passivehouse, ATTMA and ISO 9972-based calculation tools to strike the right balance, ensuring accuracy from the first setup.