I have a cabin, and this trip, it was COLD up there. I noticed several
major air leaks, which I addressed with gaskets, wiper gaskets, and
I saw a program once where they used smoke to detect leaks. They had IIRC a
piece of cotton rope that gave out a wisp of smoke, and this wisp followed
any air flow.
Would I put a good sized fan outside blowing in to create positive pressure
inside, or put it exhausting out to create negative pressure in order to
follow the wisps of smoke and see where to chink and caulk?
Thanks in advance
My guess is you'd have better luck blowing in from the outside. It would
be more work; you'd have to aim the fan where you suspect there might be
a leak, then check it on the inside. But putting the fan inside would
likely cause so much turbulence it'd be hard to tell whether the smoke
wisps were being blown by the fan or by a leak.
Just as McDonald\'s is where you go when you\'re hungry but don\'t really
care about the quality of your food, Wikipedia is where you go when
Exhaust out, on a cool day. Put a $65 Kestrel 1000 air velocity meter in
a partially opened hallway window and open and close some doors to rooms
to find out where to airseal first, and watch the incoming air velocity
increase as you seal up leaks.
Google is your friend. I googled this up. You overpressure the house, and
then the smoke will flow right towards the leak. It showed a blower that
goes into a window space.
I looked at smoke pens, and boy, are they expensive. I think I will use a
cotton cord, or dig out some of the Patchouli incense sticks left over from
the hippie years.
Apparently your friend Google is putting you on. The way you mentioned
is contrary to the standard procedure, and for several reasons. This
is the standard way, and the US DOE isn't known for pulling your leg.
If you use a small fan it won't have as much effect in the far reaches
of the house, so generally they use very powerful fans which would drag
in a lot of undesired stuff along with the desired air pressure
differential and blow your stuff all over the place. Think dust storm.
If the house is put under negative pressure, all of those little gaps
and cracks work essentially as a filter to keep out most of the
undesired dust, pollen, etc.
Also think how the smoke is used in detecting the leaks. In your
scenario you can't hold the pencil right up against the suspected area
surface because the smoke movement wouldn't be as noticeable traveling
just a fraction of an inch. If the air is being sucked in to the house
the smoke travels inwards and there's a nice smoke plume.
There are definite advantages to the smoke pencils, pens, bulbs,
ampules and other dedicated devices. The pencil smoke is lighter and
is a more sensitive test and it won't stink up your house. There are
cheaper alternatives such as
but even if you buy a pencil that costs 50 bucks, you could sell it on
eBay when you're done with it and get most of your money back. Think
of the higher initial cost as a refundable rental deposit. Google
seems to be messing around with you today. ;)
Now, I'm confused. If air is being sucked into the house from outside,
wouldn't the pressure inside be greater, and the plume go towards the leak?
Wouldn't the fan have to be sucking air out of the house in order for the
smoke to travel inwards?
I guess it's this simple:
Do you want the smoke to blow towards you, or have it blow towards the leak?
Even on Google, I found directions stating to do it both ways.
Sorry. I should have made that sentence clearer. The fan is indeed
sucking air out of the house, and the leaks are allowing air to be
sucked in through them.
It's preferable to have the house in negative pressure as that is how
the air leaks work. Air infiltration, just as the name implies, is
unwanted air entering the building. So to recreate the leaks at an
amplified rate to make it easier to detect them, the house should be in
negative pressure with the fan sucking the air out of the house.
That's why Google, while being your friend, also hits on your
girlfriend sometimes. Never turn your back on Google.
Heck, I did a walkaround when it was 9 degrees outside, and I could feel
drafts. In some places along side the beams, I could actually see daylight.
This is going to be quite a long process, probably starting with the biggest
leaks and working back from there. Good news is that the way this was rough
finished, it is easy to pull off the trim pieces to get where I believe most
of the gaps are. Then just renail the strips, or even perhaps put some
better looking trim instead of the rough one by's.
Under "see daylight" you might appreciate this story. This summer a
buddy decided time to refinish the cabin. Figured he'd save some time,
picked up a power washer, and ... well ... was his wife pissed when she
came home and did that walkaround inside the cabin.
Dunno if this is useful, but I find those plastic grocery bags pack
very nicely into cracks and crannies stopping drafts. Just use a
trowel, putty knife ... probably an ordinary kitchen knife would be
ideal ... to work them in.
Before you do that, take one out back and hang it from the clothesline,
twisted up all tight, and light it. (Shove it in a pipe if you want to more
closely simulate installed conditions) Most cheap plastic like that supports
flame real well, and can wick it into crevices.
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