Blower door testing with exterior vents sealed or unsealed?
Should all exterior openings be sealed or open during a blower door test?
When my GC did the first test (they had their own staff do the test) it was before drywall but all the exterior vents were sealed shut with Rissan tape. Now they want to do the final test but we still have the intake and exhaust air openings taped over and without the proper exterior hoods yet. They have scheduled it for this week but I’m not so sure.
I think it is pretty misleading to say a house is ___ ACH50 when the large holes the HVAC are sealed shut. As soon as the HVAC is completed with the exterior hoods and dampers, those openings will not be covered with Rissan tape so I don’t understand why they would be during the test.
Just curious what is standard practice, I’m not sure if it is unreasonable to tell my GC to reschedule the testing once exterior vents are unsealed.
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Hi Izzza,
I think it depends on what your testing. If your builder is testing his envelope and checking his work, it may make sense to keep the penetrations sealed up when he tests. If your testing for a code compliant test, then it needs to be done differently. You can do a simple Google search and find the code section. I could see an argument for doing it many different ways, depends on what your goal is in testing. Good luck!
Good point!
Well I think the mid-construction test was to check the work as that would allow them to locate any leaks with penetrations sealed. Since it achieved our goal of 0.6 it seemed fine.
My goal in paying for another blower door test is to find out the air leakage in the finished house, which is why I thought it made sense to have penetrations open like they will be during occupancy.
Normally you seal any atmospheric vents, such as those for naturally aspirated water heaters and the like. Assuming you mean things with dampers (bathroom fans, clothes dryers), I would run the test WITHOUT sealing those -- that way you test the effectiveness of the dampers too.
My preference here would be to have the test run twice on the same day. Get everything ready for the test the day prior, sealing up all the vents -- including those that have their own dampers. Run the blower door test. Immediately after getting a result, remove whatever you used to seal over any vents with dampers and run the test again. This shouldn't cost much more, since the tech is already setup and on site. Having two numbers like this will tell you how well the dampers are working, since you'll have "with" and "without" numbers for those. If the numbers with the dampers un-sealed are much worse, you know you have to do some work on those dampers.
Bill
Thanks Bill! We don’t even have the little exterior hoods on yet (for the ERV intake/exhaust) but it’s a pretty big opening to exclude completely.
I will suggest installing the hoods before testing so that way we could just tape those up to do an additional test.
I also wanted to test depressurization with the range hood running and that seemed like something we do with the blower door equipment (not sure). It would be good to see how the exhaust impacts the air at different speeds and maybe with a window open and shut. Seems like it’s best to just wait until we have the range hood situation figured out and do the testing all at once since I think we’re just paying hourly for the guy’s time to do it as they own the equipment.
Yeah, you need to install covers/flashing/etc. on any big holes prior to blower door testing. The idea with the blower door is to test air leakage for the final project configuration, or sometimes at stages as the project progresses. Big holes that "aren't quite done yet" will give inaccurate test results.
The manometer the blower door tech has should be able to tell you about depressurization with the range hook running, but you'd need to have everything pretty much done before that test could be run.
Bill