Your red arrows should indicate inward leaking air at the windows if the house is being depressurized by a blower door.
Needs work.
Don’t try to re-invent the wheel. There are hundreds if not thoussands of good graphics about air leakage and blower doors.
poor illustration…
An anigif with infrared showing the correct airflow would whoop it up some!
Thousands. Really? Where?
If I had a gun to my head, I couldn’t find five, online, equivalent to http://www.nachi.org/gallery/insulation_and_energy/general/blower-door.jpg, which BTW is excellent.
I think this new image is much better (at least for my purposes). I needed an image that can be used in marketing pieces or InspectorPages sites to quickly convey (in layman’s terms) what a blower door is… and… the image had to look good.
Now for member purposes, the other reason we need our own good-looking images is so that members can use them (without fear of copyright infringement).
It fails, Nick.
Prettier picture of a house, indeed…but the information it conveys is incomplete and incorrect.
In the training manuals and some government online stuff…more about the air leakage sites though!
Jim, how is the information it conveys “incorrect?”
Just for starters…during a blower door test all buffer zones (garage, attic, unconditioned basement, porch, crawlspace) should be open to the outside.
Remember, Nick…a blower door test quantifies the air exchange rate between the conditioned area of the home and the outdoors. For proper measurement, all unconditioned space should be allowed to match exterior pressure.
There is much more…but takes too much time to post.
How could we convey that in an image? What if we removed the word “leaking” from the yellow arrow in the key? In other words, change “Inward Leaking Air” to “Inward Air” or “Incoming Air.” ??
Would that help?
Starting with a full understanding of what a blower door test actually measures, I think your illustration should show a cross-section of the interior (not exterior) of the home. It might point arrows at common leakage points between conditioned and unconditioned spaces, perhaps, but the entry points are secondary to the blower door test and the information it is designed to provide.
Using an exterior view of the home is of no value since air actually leaks through construction materials during a blower door test. 5/8" OSB will leak at the rate of .09 CFM for ever 100 sq ft when the blower door is depressurizing at 50 Pa.
Hm. But does the purpose of a blower door test have anything to do with the leaks through construction materials such as OSB… or is it to find leaks the home owner can do something to address?
The purpose of the blower door test is to measure the exchange of air between conditioned and unconditioned spaces. That is all that it does. In the depressurization mode, it will draw air from wherever it can…through OSB, drywall, air barrier paper, windows, attic bypasses, etc. It is measuring the exchange of air with the outdoors through all sources of entry and exit so, yes, the leaks through construction materials is relevant.
The 2009 IRC requires builders to use a blower door test to measure ACH under certain circumstances for this reason and others.
During the blower door test, with the use of thermal imaging and other devices, points of air leakage can also be identified and documented for sealing the leaks. After the leaks have been sealed, additional blower door testing is necessary to (1) measure the effectiveness of the weatherization efforts and (2) ensure that a sufficient amount of ventilation is still present for health purposes and proper venting of fossil fuel burning devices, if present.
Blower doors work just as effectively in providing their intended data by pressurizing the house as they do in a depressurizing mode. In the pressurization mode, your arrows would be reversed.
So would you say that it’s main purpose isn’t to identify leaks, but rather test to see how successful actions to seal leaks were?
It’s main purpose is to measure the exchange of air between conditioned and unconditioned spaces.
This is done prior to and after weatherization efforts.
Are you able to come up with a reason (in text) for a home owner to have one done? From there I might be able to figure out a graphic that represents it.