Today I received a request to test 4 units for a small apartment building. He says the building is 32x52 which is 1560 SF. There is 4 apartments which are 1 bedroom and living room plus bath and small kitchen. If I test each unit, I suspect they are approx 400 SF. These units will have to be very tight. He wants me to open all the doors and test from one end of the hall. I have never done this is 10 years so not sure this is kosher.
Scott Katznelson In 2013, I had my HERS Field Review completed on a multi-family unit. I did and end unit, and my QAD set a blower door in the adjacent unit. We tested both units. The difference between guarded and unguarded was less then the +/- variance in the Multipoint Tests. I have been involved with 3 more multi-family units since then. I have tested at least one unit on a guarded / unguarded basis for comparison.I have consistently obtained results with this variance. If you observe the construction and air sealing before you test, you will eliminate the problems before you have to fix them. We do need to get a firewall determination for all of these firewalls about what products are acceptable for air sealing. That was the biggest problem I had with the 28 units this year.
Most of the work I do is retrofit of older buildings. Marriage wall leakage is often significant, although typically more through duct leakage between units than through the wall itself.
The way we'd normally do this is to mount one blower door in the hallway, then a duct tester blower door in the individual unit. You'd first test the total leakage of the unit with adjacent apt windows open which will give you the total leakage of the apt. Then you turn on the hallway blower door so the hallway pressure equaled the apt pressure the reduction you see if the wall to the hall. Then open one apt door and close the window and the change is the shared wall, repeat for apt on the other side and you see the reduction as the shared wall with that apt. Now you've got leakage to outdoors which has the leakage between floors included but that should be small.
Alternatively, one blower door in the hallway could be used to measure the total leaks of all four.
What's important is to understand what they/he want to measure. Once clear on that, we can come up with a way to measure it.
Thank You, Colin! Those are very good points and processes to do some Zone Pressure Diagnostics techniques applied to multi family buildings.
Interesting subject and many good answers. Thank you Jerry for the question.
I have never ran into this but have a good understanding of the concept My first thought was with as small as it is to simply test it as one unit. But Scott made a good point and the data might be good overall with a one door test for all. But five blower doors in 1500 sq ft seemed inefficient yet accurate.
Colin's approach which lets face it we are lucky to have his knowledge rolling onto the post made allot of sense. it use the tools in a basic professionals box which the only thing that might not be standard is a frame and cape for a duct tester and provide zone techniques with accurate measurements.
I have copied and pasted his answer in case I need it for future reference or I want to look exceptionally smart on a board one day in the future.
Great discussion and thank you to all.