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According to Marc Rosenbaum, Henri Fennell, and others who use the test all the time, it works very well, and the fog does not get hung up on insulation.
One main advantage of this trick: subcontractors rarely talk back when the energy consultant points to the fog. There isn't any arguing. The usual response is something like, "Holy Cow! Look at the fog pouring out of the soffit! Let's find the problem and fix it."
Cool. I'll have to look more into it. What a great excuse to own a theatrical fog machine, too. Lookout Halloween!
Charles, Even though the fog is oil-based, there's very little of it. the amount of actual oil used would be so small that any plate-out on the inside of the house would be almost unmeasurable. OTOH, it might be enough to make you fail a VOC test for LEED qualifications. That would bite.
All complex problems have a simple solution. That solution is invariably wrong.
Peter Engle, PE
Almost Home, Inc.
www.almosthome.com
what is the ASHRAE-accepted cutoff point in a blower door test at which mechanical ventilation would be required?
The Minnesota standard is minimum 1200 CFM50 (4.5 ACH50 for a 2000 sf house), and the Wisconsin standard is minimum 1500 CFM50 (5.63 ACH50 for a 2000 sf house). With both standards in their respective climates, the average new house would achieve approximately the ASHRAE minimum standard of 0.35 ACH natural.
They make non-oil based fogging solutions now. Glycerin maybe? I know ours is not oil. We use it for duct test training also.
Darrell, can you find out the make and model? A fog machine can be very usedful but not if it makes a mess of the home. If a home is contaminated with aerosolized droplets of anything that does not readily evaporate and attracts soiling particulates such as soot, starch, skin cells, etc. that show up as "soot" or Black Particulate Matter.
Thx,
Hearthman
Darrell, can you find out the make and model? A fog machine can be very usedful but not if it makes a mess of the home. If a home is contaminated with aerosolized droplets of anything that does not readily evaporate and attracts soiling particulates such as soot, starch, skin cells, etc. that show up as "soot" or Black Particulate Matter.
Thx,
Hearthman
That is part of the reason infrared is a much better option. Fog can also move somewhat like water. Meaning the leak is not always exactly where the fog is coming out of the structure. It is very visually exciting to see, but so is IR.
I've also heard from people who recommend performing both types of tests that pressurized (blowing out) tests are better for finding potential flashing mistakes and future water leaks, because sucking air often pulls flashing and construction layers together temporarily and obscures lurking problems.
Jesse Thompson
Kaplan Thompson Architects
http://www.kaplanthompson.com/
Portland, ME
IR thermography is a great tool but like all tools, it is not an end to itself and thus has its limitations. IR cannot show airflows unless that air has some sort of gas that is at a temperature above or below the surrounding surfaces. IR cameras are used from helicopters to spot high pressure gas leaks in transmission pipelines due to the frigid temps of escaping gas.
IR can demonstrate air or flue gases escaping only if there is sufficient latent heat in the water vapor therein or how this leak changes temps. of adjoining surface temps.
If you use a fog machine, you have to be scanning all over as you begin the test to spot leaks quickly. If you focus too long on any one leak, you may miss another only to find an entire compartment flooded making it very difficult to localize the leak. IR will show the temp. gradient so you can track it down.
Blower doors, micromanometers, TiCl4 puffers, fog machines, and IR thermography make an unbeatable team.
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