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Employed to determine airtightness, the blower door test is an important tool during the retrofit process of any project. An initial test provides data on the existing structure and is integral to assisting in the redesign of the building. During construction, after upgrades to the air barrier are completed, a second test is conducted to verify that the work was done properly. This test may be repeated until the test shows conformance with the contract documents.
In the case of the OAA HQ Renew + Refresh project, four blower door tests have been conducted over the past seven years. In April 2012, airflow into the OAA Headquarters was approximately 0.91 L/s/m2 at 75 Pa. Airflow out of the building was approximately 0.92 L/s/m2 at 75 Pa. These initial results showed that the building was actually remarkably tight—it would more than meet the stringent target set by the U.S. Army Corps of Engineers for high-performance buildings. The results were largely the same in November 2016, when a blower door test was performed to gauge the building’s performance before the renovation project began.
Almost three years later, as the Renew + Refresh project was being completed, CoEfficient Building Science Ltd. set out to quantify the air leakage through the building enclosure and qualitatively identify the sources of air leakage with thermographic scanning. In October 2019, architects and members of the media were in attendance to view a blower door test at the headquarters building. The purpose of this test was to determine the post-retrofit air leakage rate at this point of substantial completion.
The average airflow rate through the building envelope was 1.40 L/s/m² @75 Pa. The latest blower door test occurred during other work that resulted in the high leakage rates, higher than the pre-renovation scores. This clearly indicates the deficiencies that must now be addressed to ensure the Headquarters can meet its intended zero net carbon performance. After these deficiencies are compiled and addressed, the intended end result is for the building to be equal to or better than the pre-construction test. To make certain the building is on track, another blower door test will be scheduled for the spring. We will keep you updated with our final results.
This type of test is important for determining the remaining air leakage deficiencies, as well as for informing the plan of action to address them. This is a critical step in the process as the OAA Headquarters also fine-tunes its building systems to reach the zero net carbon goals.
Airtightness tests are useful during the design process for new buildings as well as retrofits—they establish quantitative expectations for a very important aspect of building enclosure performance and provide a key input into the mechanical designer’s load and energy calculations. Blower door tests are an important tool for architects to consider, as they help confirm that airtightness targets are met and, if timed properly, afford the opportunity to identify and address efficiencies.To read CoEfficient Building Science Ltd.’s full report on the test, click here.