Commercial Blower Door Testing – GreenBuildingAdvisor

By Jon Harrod | August 22, 2025

Code requirements for airtightness in commercial buildings are becoming more stringent. In 2019, the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) updated ASHRAE 90.1, “Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings,” to require blower door testing in most commercial buildings. In 2021, the International Energy Conservation Code (IECC) also made blower door testing mandatory for most occupancy types and climate zones. More recent editions of ASHRAE 90.1 and the IECC have extended the range of buildings that require blower door tests and reduced the maximum rates of air leakage allowed.

ASHRAE 90.1 and the IECC serve as model codes upon which most state energy codes are based. Many states still follow earlier editions of these codes, which treat blower door testing as an optional compliance path. In the older versions, air barrier requirements could also be met by using approved materials and inspecting the air barrier for continuity.

As states update their energy codes, commercial blower door testing will become more common. A blower door test measures the overall tightness of a building in a way that a visual inspection cannot. It also exaggerates air leaks, making them easier to find and seal. Testing benefits building owners and occupants, who will experience lower energy bills and more comfortable spaces. Improved airtightness will also reduce mold growth, structural rot, freezing pipes, and other building failures caused by air leakage.

For those already using blower doors in small residential buildings—energy auditors, raters, and home performance contractors—the new commercial requirements present a business opportunity. Many of the skills and building science principles used in testing one-to four-family homes carry over to commercial work. But there are also important differences. Here I’ll share my experiences as a residential contractor who’s moved into commercial testing. I’ll focus on buildings like offices, stores, laboratories, and…