Attic fan/humidistat question
 

Hello,
An attic fan has died (moment of silence). The device that is
currently installed is a thermostat-driven electric exhaust fan. I'm
looking to determine whether the fan even needs to be replaced or to
simply leave the opening as-is as a passive vent (it looks like the
motor cannot be removed without going on the rooftop, which may not be
an option). The details a

- The house is in Western NY.
- Insulation was professionally installed in June into the attic.
- Last summer, the temps climbed into the high 80's-90's for maybe a
week or two with the attic reaching ~110-120 for maybe a handful of
days.
- The winters can be cold for a few months.
- There appears to be adequate soffit vents to the attic area.

I'd like to determine the need before the brutally cold weather hits,
but I am looking for more specific information related to temperature,
humidity, etc. With the additional insulation and the short time
within the house, I do not have current visual gauges regarding
previous moisture. There does appear to have been previous moisture
issues but the insulation that was in the house had been improperly
installed.

My questions a
1. I understand from other posts that temperatures that reach ~120 or
higher can be the beginning of the damage-inducing range. Is this
over generally considered the norm in hot climates (i.e., 120 all
summer), or an "if it ever reaches, assume the worst" guideline?

2. Is the rule-of-thumb in the NE to get a humidistat? I was
thinking of buying a bare-bones humidistat and just recording the
values over a few weeks, but have not found a guideline (i.e., if it
is consistently above x%). Or, would visual inspection be enough
(i.e., if you see moisture, get a humidistat, if not you should be
fine)?

Am I overanalyzing this to to death? Probably. I apologize.

TIA,
Dave

In winter passivly vent, if you have signs of condensation or mold
increase venting, attic temps should be near outside level. A drawback
of powered vents is removing conditioned interior air because makeup
vents are to small and most attics are not sealed from the lower area.

Dave wrote:
Hello,
An attic fan has died (moment of silence). The device that is
currently installed is a thermostat-driven electric exhaust fan. I'm
looking to determine whether the fan even needs to be replaced or to
simply leave the opening as-is as a passive vent (it looks like the
motor cannot be removed without going on the rooftop, which may not be
an option). The details a

- The house is in Western NY.
- Insulation was professionally installed in June into the attic.
- Last summer, the temps climbed into the high 80's-90's for maybe a
week or two with the attic reaching ~110-120 for maybe a handful of
days.
- The winters can be cold for a few months.
- There appears to be adequate soffit vents to the attic area.

I'd like to determine the need before the brutally cold weather hits,
but I am looking for more specific information related to temperature,
humidity, etc. With the additional insulation and the short time
within the house, I do not have current visual gauges regarding
previous moisture. There does appear to have been previous moisture
issues but the insulation that was in the house had been improperly
installed.

My questions a
1. I understand from other posts that temperatures that reach ~120 or
higher can be the beginning of the damage-inducing range. Is this
over generally considered the norm in hot climates (i.e., 120 all
summer), or an "if it ever reaches, assume the worst" guideline?

2. Is the rule-of-thumb in the NE to get a humidistat? I was
thinking of buying a bare-bones humidistat and just recording the
values over a few weeks, but have not found a guideline (i.e., if it
is consistently above x%). Or, would visual inspection be enough
(i.e., if you see moisture, get a humidistat, if not you should be
fine)?

Am I overanalyzing this to to death? Probably. I apologize.

TIA,
Dave

I suggest first making sure you have good passive venting and that
leaving the fan in place is not going to short circuit the passive venting.
In most situations passive venting does a very good job if properly
designed. Power venting is seldom required except where the passive venting
was not properly designed or is defective in some way.

Next time you re-roof eliminate the old fan.

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math

"Joseph Meehan" wrote in message ...
Dave wrote:
Hello,
An attic fan has died (moment of silence). The device that is
currently installed is a thermostat-driven electric exhaust fan. I'm
looking to determine whether the fan even needs to be replaced or to
simply leave the opening as-is as a passive vent (it looks like the
motor cannot be removed without going on the rooftop, which may not be
an option). The details a

- The house is in Western NY.
- Insulation was professionally installed in June into the attic.
- Last summer, the temps climbed into the high 80's-90's for maybe a
week or two with the attic reaching ~110-120 for maybe a handful of
days.
- The winters can be cold for a few months.
- There appears to be adequate soffit vents to the attic area.

I'd like to determine the need before the brutally cold weather hits,
but I am looking for more specific information related to temperature,
humidity, etc. With the additional insulation and the short time
within the house, I do not have current visual gauges regarding
previous moisture. There does appear to have been previous moisture
issues but the insulation that was in the house had been improperly
installed.

My questions a
1. I understand from other posts that temperatures that reach ~120 or
higher can be the beginning of the damage-inducing range. Is this
over generally considered the norm in hot climates (i.e., 120 all
summer), or an "if it ever reaches, assume the worst" guideline?

2. Is the rule-of-thumb in the NE to get a humidistat? I was
thinking of buying a bare-bones humidistat and just recording the
values over a few weeks, but have not found a guideline (i.e., if it
is consistently above x%). Or, would visual inspection be enough
(i.e., if you see moisture, get a humidistat, if not you should be
fine)?

Am I overanalyzing this to to death? Probably. I apologize.

TIA,
Dave

I suggest first making sure you have good passive venting and that
leaving the fan in place is not going to short circuit the passive venting.
In most situations passive venting does a very good job if properly
designed. Power venting is seldom required except where the passive venting
was not properly designed or is defective in some way.

Next time you re-roof eliminate the old fan.



I agree, it depends on what other outlet vents there are besides the
power fan. I think a ridge vent combined with soffit vents is the
best solution. If you only have two gable vents, then it's likely the
fan will be a help in the summer. As far as humidity goes, you can
get by with less ventilation than that required for heat removal. In
a northeast climate, I have yet to see an attic where a fan was needed
for humidity issues. If you have any humidity issues, I'd check to
make sure there is no source for humidity, like bathroom or dryer
vents that improperly terminate in the attic.

And I'd have to disagree with an earlier post that said the attic
temps should be near outside temps. On an 85 degree day in full sun,
this isn't realistic. The temp goal of attic ventilation is to
prevent extreme temps, like 120+, which can lead to premature roofing
failure and increase air conditioning reqts. It's not unusual for a
properly vented attic to be over 100 on a hot day, which the the
insulation can easily handle