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