What is Building Envelope testing?

The Clark County Portal list this as “Building Envelope” but the full name of this should be “Building Envelope Testing”. This is a “Condition of Approval” that many contractors see in their Citizen’s Access Portal in the Clark County jurisdiction.

The thermal envelope generally consists of all the walls that have the “Conditioned Space” on one side of the wall, and that have either the

• Outdoors

• Garage

• Attic

• Crawlspace

The goal of this test is to ensure that a “small amount” of air in capable of leaking through the building’s thermal envelope. The test involves temporarily installing a powerful fan in an exterior door frame of a building, which is then used to depressurize or pressurize the building. By measuring the airflow required to maintain a certain pressure difference between the inside and outside of the building, technicians can determine the air leakage rate.

During the test, the technician typically closes all windows, doors, and other openings in the building except for the one with the blower door. The fan creates a pressure difference between the inside and outside of the building, causing air to flow through any leaks in the building envelope. The airflow rate is measured using a pressure gauge, and the results are typically expressed in air changes per hour (ACH) or in cubic feet per minute (CFM) at a certain pressure difference.

Blower door testing helps identify areas of air leakage in a building, which can lead to energy loss, discomfort due to drafts, and decreased indoor air quality. Once these areas are identified, they can be sealed to improve energy efficiency, comfort, and indoor air quality. Additionally, blower door testing is often used to assess the effectiveness of air sealing measures after they have been implemented.