Public demand is growing to make residential homes more airtight, which saves homeowners money and lowers carbon emissions. The same is true of large buildings—not only multi-family residential buildings, but also offices, hockey rinks, warehouses, factories, and garages. But is airtightness testing in larger buildings just a matter of scaling up the procedures for a family home?

While many of the same principles apply across all buildings, the consensus of experts in airtightness testing is that size does matter.

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Why test?

The main reason for airtightness testing in large buildings is not much different than for single-family homes: building owners want to save on costs. “The difference is that these buildings are typically owned by companies or individuals that rent out the spaces and are covering all those operational costs,” says our Director of Building Science, Mark Rosen. “Those energy losses may be directly impacting their budget.”

Building incentives offer another reason to conduct airtightness testing, says Kyle Anders, our Senior Project Manager for Large Building Testing. He points to a variety of standards that can qualify a building for incentives: “We’ve done a lot of compliance work for ENERGY STAR® that applies largely to smaller homes and low-rises but above three storeys it’s more about the commercial construction code and the ENERGY STAR® Multifamily Program.”

In the Canadian market, much of the demand for large building airtightness testing comes from building owners or builders who are working with commercial-scale energy modelers. There is also some demand from owners of existing buildings, particularly from industrial clients who want to benchmark the airtightness of their buildings for future comparison.

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Variety in large buildings

It might seem that testing larger buildings would just be a matter of scaling up a blower door test, but size can add to the complexity. There’s a huge variation in form: some buildings are skinny and tall, some big and square, some low and flat. This can produce a lot of variation in stack effect—the tendency of warm air to rise, causing heat to escape through the upper storeys, while cool air leaks in through the lower levels.

On the flip side, a million-foot-square Amazon warehouse might be only one and a half storeys, so while the stack effect isn’t an issue, keeping a building of this size airtight still has its many challenges, such as isolating parts of the building that are used for vastly different purposes, or ensuring airtightness when part of the building that is meant to be open, such as a garage. Measuring and modeling during the design and construction phase can avert some of these challenges, while benchmarking after the fact can help building owners keep on top of the issue—and even help with reselling the building.

Large buildings’ mechanical systems are frequently much more complex, so it’s also necessary to understand how they function, and what parts of them need to be sealed or left open for the test.

Finally, older large buildings can bring out some surprises that don’t often happen in single-family homes. In one memorable case, BKC technicians were trying to isolate a zone in a building, when we discovered a hidden connection through a bench and a subterranean tunnel that no one knew about: it led to another building altogether.

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Differences in testing

Given the variety of buildings, it follows that airtightness testing will be more complex at larger scales. First, the standards are different: the usual test for air changes per hour (ACH) in homes becomes normalized leakage rates (NLR) in large buildings. Second, larger buildings are usually tested at higher pressures. In low-rises, it’s usually 50 Pascal, but it goes up to 75 for commercial buildings.

In that case, a few fans at one door aren’t going to provide enough pressure. As Michael Gilezan, our Manager of Technical Field Services, puts it, “It’s similar equipment, but a lot more of it, and they have to work in concert through a central laptop. We’re potentially connecting 15 pieces together with specialized software.” Michael notes that such tests also have human complications: there will be more people on the job and 90% of it is done off-hours, so our technicians are in the building when it is not in use. Large buildings also require more support to prepare for the test.

Another unique aspect of testing large buildings is compartmentalization. While whole-building testing is important, it may be necessary to isolate individual zones, such as a single floor of an apartment building or an area of an industrial building where fumes must be contained. Compartmentalization is also important when there is a significant stack effect—which can be strong enough to hold doors shut on the ground level.

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Need to know more?

Building Knowledge Canada has extensive experience in airtightness testing on a wide range of large buildings and we help building owners and builders develop techniques and processes to make the systems and technologies in their buildings work—for increased comfort, energy efficiency, durability, and cost-effectiveness.

While we focus on measuring first and foremost, we also offer detection of air leakage locations (through smoke tracing, infrared scanning, sense of touch), so that you can know where the leaks are happening and then strategize internally on how to seal them.

Our Large Building Enclosure Testing page provides. more information about applicable codes and programs, as well as an energy-saving calculator.

If you have any questions about airtightness testing or our services, feel free to reach out to us directly.