While I still think it's possible the mold growing on my attic ceiling on
the roof sheathing may stukk be a special case scenario, such as snow
sitting on the roof on a winter day when the temp and humidity high, I'm
starting to agree that my attic does, in general, need more ventilation,
even if my adding the ventilation doesn't wind up solving the mold issue.

The reason is because my attic's internal temperature, as measured near the
attic's ridge, was 105 degrees today. Today, in the northeast, it's a
perfectly sunny day. Outside, the temperature is only 62 degree in the
shade, and the temperature in direct sunlight was measured at 96 degrees
(likely would be a bit higher without some breezes).

Is a 105 degree attic temperature (as measured near the attic's ridge), on a
day such as I just described, a normal attic temperature for a properly
ventilated attic? If not, what would my attic's temperature be if it were
properly ventilated. (My attic is a crawl space, meaning you can't stand up
in it.)

As for humidity, I haven't yet seen any indication humidity problem in my
attic, as measured by a hygrometer. I still think mold growth may be a
special case, such as a snow-sitting-on-roof scenario described above, or if
there were several very high humidity days in a row. In other words, I'm
not seeing much evidence of high humidity in my attic, although it likely
does need more ventilation as indicated by today's 105 degree attic
temperature.

Let me know what you think.

Thanks.

Jeff

105 is way to high for 62 , i was just in my attic its 74 out and maybe
78 in the attic. Of course you wont see high humidity , humidity goes
down as the temp rises. The concern is temperature Differential between
the attic and the outside. That is where conensation forms , at the
Coldest spot. Your roof deck. Just like windows condense water in the
winter the same is happening in your attic.
Ultimatly your attic should be no warmer in winter than the outside, or
condensation will form, than mold than rot. VENTILATE as others said
before. And bleach in a garden sprayer will kill the mold After you
ventilate.

jeff wrote:
While I still think it's possible the mold growing on my attic
ceiling on the roof sheathing may stukk be a special case scenario,
such as snow sitting on the roof on a winter day when the temp and
humidity high, I'm starting to agree that my attic does, in general,
need more ventilation, even if my adding the ventilation doesn't wind
up solving the mold issue.

The reason is because my attic's internal temperature, as measured
near the attic's ridge, was 105 degrees today. Today, in the
northeast, it's a perfectly sunny day. Outside, the temperature is
only 62 degree in the shade, and the temperature in direct sunlight
was measured at 96 degrees (likely would be a bit higher without some
breezes).

Is a 105 degree attic temperature (as measured near the attic's
ridge), on a day such as I just described, a normal attic temperature
for a properly ventilated attic? If not, what would my attic's
temperature be if it were properly ventilated. (My attic is a crawl
space, meaning you can't stand up in it.)

As for humidity, I haven't yet seen any indication humidity problem
in my attic, as measured by a hygrometer. I still think mold growth
may be a special case, such as a snow-sitting-on-roof scenario
described above, or if there were several very high humidity days in
a row. In other words, I'm not seeing much evidence of high humidity
in my attic, although it likely does need more ventilation as
indicated by today's 105 degree attic temperature.

Let me know what you think.

Thanks.

Jeff

Classic case of too little ventilation. Even low relative humidity
(like 40%) may be a serious problem when the roof is cold. You need to
figure the dew point. If the roof is less than the dewpoint you have too
much humidity.

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math

Wow...hard to believe your attic is only 4 degrees hotter than the outside
temperature. Is your attic's roof completely under direct sunlight and is
it a perfectly sunny day? I just find it hard to believe that an attic
could only be 4 degrees hotter than the "in-the-shade" temperature on a
perfectly sunny day if the roof were totally under direct sunlight with no
shade. Is your attic a screen porch? g Does your attic have white
colored shingles? Are you sure your attic's roof wasn't at least partially
in the shade?

While I agree it's getting too hot in my attic, keep in mind that, on an
overcast day, or at night, my attic's temperature gets, from what I can
tell, no more than 7 degrees higher than the outside "in-the-shade"
temperature. I do agree I need to ventilate to get my attic closer to the
"ultimate" level of zero degrees higher than the outside temperature on a
cloudy day or at night, and also to prevent those ultra-high over 100 degree
readings on perfectly sunny days. But my impression is that it's only
realistic to expect the attic temperature to be equal to the outside
temperature on cloudy days, or at night.

Of course you wont see high humidity , goes
down as the temp rises. The concern is temperature Differential between
the attic and the outside. That is where condensation forms , at the
Coldest spot. Your roof deck. Just like windows condense water in the
winter the same is happening in your attic.

Well, I agree this could potentially happen at night if the attic happened
to already contain very humid air and the roof deck were to cool off at a
faster rate than the attic's internal temperature. My attic seems to cool
off rather quickly at night though. For example, tonight, humidity in the
attic did not appear to be an issue. It's currently 11pm and the attic's
temperature has cooled off to only 55 degrees which is only 7 degrees higher
than the outside temperature. The attic's relative humidity is only 26% so
there doesn't currently appear to be a humidity problem as measured by the
hygrometer. The sheathing does not feel moist. If there's a humidity
problem in my attic, then I still suspect it may be a special case
scenario, such as snow sitting on the roof in the winter on a very humid and
very warm winter day. Or perhaps a hazy/hot/humid day in the summer, in
which the attic contains very hot air and suddenly there's a rain shower
which cools the roof off very quickly before the attic gets a chance to cool
off. In that case, then I agree that better ventilation would help the
moisture escape more quickly. Another special case scenario would be if
there were several consecutive days of hazy/hot/humid weather in the summer.
In 2003 we certainly had one of the most moist years ever in terms of rainy
and humid days.

Anyway, I do plan on ventilating more and very soon, but I'm just trying to
analyze and study the situation to try and pinpoint the exact scenario in
which the mold is growing.

Ultimatly your attic should be no warmer in winter than the outside, or
condensation will form, than mold than rot. VENTILATE as others said
before.

Well, I agree my attic could use more ventilation simply because the
temperature gets too hot on a very sunny day. Other than the fact that
mold is there, I still haven't seen any evidence of condensation happening,
or even evidence of too much humidity as measured by a hygrometer near the
attic's ceiling. I agree it can't hurt to ventilate more if only to make
my attic's temperature even closer than the 5-7 degree difference (when not
in direct sunlight).

And bleach in a garden sprayer will kill the mold After you
ventilate.

Okay, but I take it that I should I put plastic sheeting down on the attic's
floor to prevent drippage onto the insulation, right?

Thanks.

Jeff

I have large gable vents and the wind was really blowing across the
water so it was cooled. Bleach wont hurt insulation it evaporates

On Sun, 28 Mar 2004 19:32:51 GMT, someone wrote:

While I still think it's possible the mold growing on my attic ceiling on
the roof sheathing may stukk be a special case scenario, such as snow
sitting on the roof on a winter day...

I am not understanding how snow sitting on the roof causes this. Snow
sits on EVERYONE'S roof in the winter. Why is that special?


The reason is because my attic's internal temperature, as measured near the
attic's ridge, was 105 degrees today. Today, in the northeast, it's a
perfectly sunny day. Outside, the temperature is only 62 degree in the
shade....

That's whack. Of course the attice temp is not gonna be "exactly" the
outside temp, but that's a lot for a 62 degree day.

Vent NOW, then fart around with your speculations afterwards.

-v.

And bleach in a garden sprayer will kill the mold After you
ventilate.

You may have better luck with ammonia and water!

I doubt it. Ammonia to the mold will be a nutrient.

Kdbcarwile wrote:

And bleach in a garden sprayer will kill the mold After you
ventilate.

You may have better luck with ammonia and water!