On Fri, 4 May 2012 05:17:18 -0700 (PDT), Limp Arbor
wrote:

On May 4, 8:04*am, DerbyDad03 wrote:
I'm looking for opinions about what I'm seeing when I smoke test my new
ridge and soffit vents.

I had my roof replaced and a ridge vent was installed. I also had full
soffits vents cut and then covered with perforated vinyl. My soffits are
about 6" wide, so there's about 4" of perforated vinyl showing.

The roof is framed such that I have about 3 feet of slanted ceilings in
the bedrooms, and the crawlspace attic itself is about 4 feet from the
top of the ceilings joists to the rim.

There is bat insulation on the floor of the ceiling that extends part
way down the rafter bays towards the soffit. When I pull the insulation
out of the rafter bays, I can see light from the newly cut soffit vents.
The contractor said that the soffits themselves are free of insulation.

I installed 4 feet of baffles in each rafter bay, pulling them back
about 4" from the soffits, per the contractor's instructions. I then put
the bat insulation back in the rafter bay making sure the tops of the
baffles are open. The insulation does not extend more than 2' beyond the
top of the baffle so I know it's not covering the soffit vent.

Last but not least, I have a 12" x 12" gable vent at each end of the
house, which I have not yet closed off.

I bought some smoke matches to check the air flow and this is what I found:

The weather conditions were mid-50's F, thunderstorm, breezy. The attic
itself was fairly cool. I closed the access staircase so the attic was
closed off as it will be under normal conditions.

Holding a smoke match up inside a rafter bay near the ridge, there was
some movement up and out, but also a lot of smoke spreading down and
across the top of the attic. The was certainly no indication of the
smoke being rapidly sucked up and out through the ridge vent.

Holding a smoke match inside a rafter bay near the top of a baffle,
there was movement up the rafter bay towards the ridge, but it seemed
more like natural up flow as opposed to strong breeze blowing it
upwards. If there was a breeze, it was not significant.

Finally, holding a smoke match within an inch of either gable vent
showed significant outflow through the gable vent. It was literally
being sucked out of the vent at a rapid pace. If I backed away from the
gable vent 4 to 5 inches, the smoke just floated upwards towards the
ridge vent.

I suspect that I need to cover the gable vents, but based on what I have
described, do I need to be concerned that the soffit and ridge vents are
not operating properly? Do I need to wait until it's really hot and try
another smoke test?

Thanks!

Not an expert but from what I've read about it you need the gable
vents closed off for the ridge vent to start the chimney effect. You
should be able to test by covering the gable vents with plastic.

The gable vents should permanently be closed off or the ridge vents will just
draw from them instead of the soffits.

When I recently re-wired my house I put fireproof caulk in all of the
holes in the basement and the attic where the wires were run. The
difference was amazing as far as temperature in the basement. The
chimney effect was obviously the culprit.

In the basement. Interesting. I've seen the wiring caulked in the attic but
not the basement.