Building Owners Are Under Pressure To Maintain Proper Pressure
The signs that a building is not operating as desired can be subtle, but we recently heard from a building owner with a very clear indicator that something was wrong: his tenants were wearing winter coats and gloves at their desks because the ambient temperature was hovering in the 30s. Because it was his first winter in his new building, he was worried that the mechanical system was undersized.
We had other suspicions that were confirmed when we broke out our infrared camera and our blower doors and got to work. Turns out the whole fascia and rake edge of the roofing system had not been tied into the weather-barrier system at all, letting outside air flow freely into the building (as heated/cooled air moved out freely as well). In the building business, we call this “a problem.” In the commissioning discipline, we call this “unfortunately routine.”
The process of designing, building and delivering a fully functional building is incredibly complex, drawing upon the expertise and efforts of multiple disciplines, from architects and engineers to construction teams and all of their subs. There are times when details fall into the cracks and little things like holes in a vapor barrier big enough to walk through can occur. Fortunately, the commissioning discipline is available to ensure the smoothest possible integration between all involved.
One of the key tests used to confirm the readiness of a building for occupancy is the “building airtightness” (BA) test which gives an overall view of the weather-barrier’s integrity (its ability to withstand penetration by rainwater or the loss of heated/cooled air) and the resulting likelihood it will stay on operating budget over time. Passing one of these tests with the proper airflow reading is an all-hands effort that starts and ends with close coordination.
We start the testing process with a meeting of all involved, ranging from the owner and architect to the contractor and HVAC installer. We discuss the steps to a successful test, including checks on typical points of failure and deciding ownership of systems and their fixes.
Key pointers we discuss include:
- Confirming the actual square footage of the building and identifying which standard of measure will be applied. (Depending on building ownership, different rates of “allowable air leakage” may be acceptable.)
- Ensuring the weather-barrier has been installed properly, in compliance with the design. The rules dictate that there can be no tweaking to this system once the test begins.
- Paying close attention to areas where the disciplines interact. For example, if the design calls for a plumber to punch through a wall or roof during an install, the air barrier/roofing contractor will need to verify that penetration has been properly flashed.
- Focusing on key transition points in the structure, whether it’s the joints between substrates or areas where vertical & horizontal surfaces intersect. The transition between the roof and wall system requires significant coordination to ensure proper drainage and airtightness are achieved together. This is often overlooked causing inadequate integration.
- Targeting all mechanical penetrations of the building envelope for sealing, whether that’s with plastic or mechanical dampers. Exhaust fans are another key point of focus.
- Checking floor drains to ensure no one is opting to tape them over as a pre-testing shortcut, instead of addressing the system configuration that might limit their integrity.
- Ensuring the actual doors and thresholds are in place (experienced contractors often leave doors off or use cheaper temporary doors during construction to reduce wear & tear by the crew.) They need to fit properly as the testing protocol doesn’t allow for them to be taped or covered with a temporary plastic sheet.
After that, we pursue consensus on the BA testing schedule so as to minimize impact on the activities of the occupants. If we test with occupants in the building, their ability to leave or enter the building will be limited to certain times when it won’t impact the results. Our longtime preference is to do these tests on a weekend so we can minimize our impact on the occupants’ activities. We ask the builder to get the word out on the testing schedule so there are minimal interruptions of the building’s routine or ours.
With those details dialed in, the target set and the team ready to test, we get rolling. Buildings don’t always pass the first time, but our techniques and equipment generate a punch list of areas where repairs are needed. This allows our project partners to jump in and tweak those systems so we can re-test, and hopefully pass on the next round.
A building with a passing BA test doesn’t just mean fewer air drafts. It can also mean reduced noise penetration in a classroom or hospital room, more consistently comfortable environments for tenants and more predictable operating budgets over time. Owners who hold off on the testing because of the cost too often find themselves with bigger problems later, so we always advocate for the “as soon as practical” option when scheduling testing.
Thinking back to the windy building at the beginning of our post, I’m happy to report that the construction contractor realized the problem had originated in his shop, so he fixed it and the owner moved forward. These days, the occupants of that building enjoy typing with their bare hands and shedding their winter coats when they reach the office. That’s what we in this business call “a success.”
By David Burks, CxA, BECxAP/CxA+BE, CAPM
David Burks is a Building Envelope Commissioning specialist who has implemented building envelope tests on over 1,500,000 sq. ft. across Kentucky.