They work well in commercial buildings, but not a lot of research has been done for multifamily.

What is a blower door test, you ask? Great question. I honestly didn’t understand what it was myself until recently. The first time I heard of blower door testing a few years ago, I (naively) thought it sounded easy. Conceptually, I loved the idea of the blower door test. A test to make my buildings more energy efficient? Yes please! However, the idea of the blower door test and the reality of it in practice are two very different animals.

Blower door testing is a test you can conduct on your building to see if you have any leaks in your building envelope. Leaks can occur through cracks, windows, wood walls, attics, attic doors and regular doors. Basically, anything in your entire building has the potential to sprout a leak.

“Why should I care?” you ask. Do you like money? If your answer is yes, then you do care. Think of how irritated you get with, say, your kids when they leave a window open in December while you’re heating the house. You think, “What a waste of money!” and use some terrific language as you shut the window and consider taking the energy bill out of your kids’ college fund. Maybe you get irritated when someone leaves the freezer door open while they scoop out ice cream on the kitchen counter. The scenario repeats itself. If this has happened to you, congratulations. You are a person with the potential to be passionate about blower door testing, and you’re curious how your conditioned air is leaving your building.

Blower door testing first appeared in several forms during the late seventies in Sweden, Canada, Texas and New Jersey to account for unidentified energy loss through leaks. The test essentially measures the air tightness of a building. Testing for air tightness has become part of the requirements for LEED Certification and some green loan programs. In some areas, it’s already integrated into the building codes.

So how does a blower door test work? It’s all about pressure. The test itself can be completed in a few different ways. The first way (and most common) is to take a sample of the units to test, open the unit door, set up a blower fan (which has plastic covering the entrance to the unit to seal it off), turn on the fan and use your manometer to measure pressure to determine if air is escaping in ways it is not supposed to (i.e. leaks). That is the most common method. You could also conduct a whole building blower door test which is similar, but instead of sealing the door to a unit, you pressurize or depressurize the entire building using multiple blower doors. All apartment unit doors have to be wide open. As you can imagine, this is not commonly done in apartments (imagine how exciting this test will be if your residents have cats). Then there is the guarded blower door test, which is technical and involves multiple blower doors running concurrently to measure leakage through the exterior wall only, negating any leakage between adjacent units.

Sarah Hill, Program Coordinator for the Association for Energy Affordability, Home Energy Rating System (HERS) rater and architect, has completed blower door tests on more than 600 units in the United States. “Most commonly (when conducting a blower door test) you find leaks in the detail work. A eighth-inch gap between the bottom plate and the subfloor around the perimeter of the unit begins to constitute a large leak when you add it up.” Sarah’s recommendations to property owners are to do a pre- drywall inspection and test early. “That way you can spot early on where the leak is during construction.”

As you can imagine, challenges often arise when conducting blower door testing in existing, occupied buildings. Jeff Shipley, community manager of the award winning 415 Premier Apartments in Evanston Illinois, a Portico managed community, recounted his experience conducting a blower door test on his property. “It was surprising to me just how invasive it was,” he related. “The test takes a couple of hours, so you are in the unit for a long time. Once you determine there is air penetrations you need to seal the leaks, and then perform the test all over again to make sure the leaks were sealed properly. Setting expectations with the residents was very important.” In addition to the unit being tested, it was important to communicate with the residents in adjacent units. “The testing was extremely loud; therefore, the residents in the adjacent units were affected by the testing as well,” he said.

But the challenges around testing on occupied buildings don’t end there. Angel Gutierrez, Regional Project Management of 550 Moreland in Santa Clara California, a Prometheus Real Estate Group managed neighborhood, shared his struggles. “Blower door testing is not as common in California for some reason. It was challenging to find a vendor who would conduct a blower door test on an apartment building. Just finding a testing facilitator was hard,” he shared. “Then it was difficult to find an experienced vendor to seal the leaks. Most indicated that our neighborhood (430 units) was too big.” It was critical to find a vendor who could effectively test in California. “You want to make sure they know what they are doing. If they don’t and you follow their recommendations, you could seal up air pathways that are engineered to be there. You could actually degrade indoor air quality and end up with a building that makes people sick.” It’s very important to have a qualified team complete the test to seal the leaks, not the designed air pathways.

Sarah Hill recounts one of her successes in blower door testing: “I did a blower door test with a fog machine on a historic building. We could actually see where the leaks were in the wall assembly. The owner was very engaged and sealed all of the leaks we identified. What was so great was not just the energy savings and health implications but by closing the leaks, the acoustics of the building changed. Residents were thrilled that not only were their units more affordable and comfortable, but they were quieter.” Happy residents equal a greater renewal rate in most markets.

Not all buildings have the same experience. Shipley explained, “415 Premier Apartments was built in 2008 and very well constructed. We really did not have significant leaks in our buildings so our residents and our owner did not have a dramatic improvement in energy savings or experience.” Gutierrez indicated that the jury is still out for 550 Moreland as his project is still in progress. “It will be interesting to find out.”

You may not have a choice in conducting a blower door test. Your renovation may trigger a code requirement, or you may be aspiring to green designation. Whatever the circumstances, I strongly encourage you to embrace this relatively new and effective way to ensure whether your building is up to par and leak-free. Make sure your test facilitator really understands what they are doing to ensure a positive outcome.


Mary Nitschke is passionate about utilities and should, perhaps, switch to decaf. She is the first president of the Utility Management Advisory Board, holds an Energy Resource Management Certificate from UC Davis, two BAs from U.C. Berkeley and is director of ancillary services for Prometheus Real Estate Group, Inc. Nitschke has the first law of thermodynamics posted by her office door, and a 1970 Lincoln Mark III with over 400 bhp in her driveway in Northern California.


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