I have a 2600 sq ft 4 level split home in Canada. It was built in
1985. This past spring we replaced our very non-effecient furnace with a
Tempstar 95% effecient gas furnace. It really is wonderful as the old
furnace would cause the house to feel sort of drafty and basement was always
cold etc... Now I have this furnace that I love to bits BUT now since it has
gotten colder outside these past two weeks, we have kept the doors and
windows closed and now have a high humidity problem inside the home IE:
fogged up windows (triple pane)...air basically feels clammy...bought a
humidistat and the house is sitting at around 50% humidity.... we use
bathroom fans in the shower, and have a fan over the stove when cooking that
we use all the time...we keep lids on pots on the stove etc...We have no
children and only the two of us in this home so no long lingering showers by
kids or anyone else....
I don't want to have to buy a dehumidifier over this new furnace..
sort of defeats the idea of trying to be energy effecient... Thinking of
trying to duct in an outside air source to feed the furnace?
Thoughts? Thanks... Jim
I guess to me it is...I also have an indoor swimming pool in the back yard
(not attached to house) and I keep the RH in that building to 30-35%...I
park my BMW in the same building with no issues.... Jim
R.H. is function of temperature. Computer room is for the machine not
people. Too low humidity will cause static discharge and it is harmful
to the machines. Here in winter, most of time at home we keep it around
25% when it gets real cold(like -30C)
Here in SE Iowa our inside RH is currently 34% and outside it is 77%. In
fact, if you want to take a look just point your browser to
www.crsales.com/weather.htm and you will see my amateur weather station.
I don't look at the inside RH that often and quite honestly I was
surprised that it was that low.
On Sun, 18 Oct 2009 21:54:32 -0400, firstname.lastname@example.org wrote:
50% is high to the Aprilaire folks-- I've been dicking around off
and on for 2 weeks wondering why mine isn't kicking on. One year old
humidifier-- new furnace install. Bought a new transformer. . .
tested where I had it hooked up. Finally read the manual again.
Max humidity is 45%. Mine is 47%.
*That's* why it has that 'test' setting.<g>
Fresh air intake is two ways, one for combustion for the furnace and one
going into return air duct. Wonder if it is damper controlled and it is
operational in your case. Too air tight home definitely needs outside
fresh air in proper amount. My house is R2000 spec. We have damper
controlled outside air intake. Yet I am running a power humidifier in
the winter. I am in Calgary that is why. Our winter air is extremely dry.
In winter, I sometimes have to run a humidifier to get the humidity up to
Outside combustion air is quite common on high efficiency units but I'm not
sure it would lower the humidity level. Right now, the moist internal air
is being used and going out the stack and infiltration is replacing it with
the outside air. You may want to experiment a bit and crack a window open in
the room with the furnace and close it off from the rest of the house.
*If the unit is the type that I am thinking of you should have two PVC pipes
coming off of it. One is for fresh air and the other is exhaust. The
exhaust pipe must be pitched (Sloped downwards slightly) towards the outside
so that condensation will drain outside and not into the unit. Check to see
if that is so. Also if your unit is not pulling air in directly from the
outside it would be a good idea to bring fresh air into the room.
On a typical condensing furnace, the PVC vent piping will slope slightly
UPWARD toward the outside,
so that the condensate in the vent will drain back thru the furnace
condensate handling system. See page 14 of the
installation instructions here for a typical system:
8. All exhaust vent piping from the furnace to termination
MUST slope upwards. A minimum of 1/4? per foot (6.4mm
per 304.8 mm) of run is required to properly return
condensate to the furnace drain system
Something does'nt add up about this post..........................
Are you saying the house was likely drier at this time last year, and this
problem is brand new?
The furnace you have now *makes* water, so to speak, but it should'nt
*contribute* to a high humidity level in the house. It should heat and dry
the air like any furnace would. The discharge air may be slightly cooler
than the air from your old one, but other wise it's pretty much apples to
apples. I would check to make sure that the furnace is not an internal
leaker, and the drain system is actually disposing of the water in a fashion
where it leaves the house. If there are no issues found with the furnace,
then I would look elsewhere for a humidity problem, if you indeed have one.
I would think that you are going to need a humidifier soon, like everyone
else, not a dehumidifier.
In fall for the first month of heating system operation I have the
same problem and so do many with tight homes. The house has to dry out
a bit. Get air to circulate, leave a few windows cracked open. Does
your home have a house wrap like Tyvek, I bet condensation goes away
in a month, open windows will help.
What did you change in addition to the furnace? Windows? insulation?
Did the furnace come with a humidifier?
The last would be my guess-- and it should have both an adjustment and
an outside sensor.
What does the installer say?
It's possible the new furnace has a seperate intake where it pulls
outside air in for combustion. The old one drew air directly from
outside, so there was always a significant amount of fresh air being
pulled into the house, at least into the basement. That would have
lowered the humidity, but now that is gone.
I agree with others who have said 50% humidity isn't excessively high
and it shouldn't make it feel clammy. It is the highest you would
want it though, otherwise you risk condensation. You wouldn't want
it that high when it's 15 outside, but by then with the furnace
running more, it's likely the humidity will decrease.
Sounds like an entirely reasonable answer.
And as the outside temperature drops the moisture content of the outside
air also drops, which should lower the inside humidity.
I don't remember it has come up, if the furnace combustion is
discharging into the house the humidity would be high. The probability
is very low for a new install, but possible. A carbon monoxide detector
is a good thing to use in any case.
On Mon, 19 Oct 2009 05:47:04 -0700, trader4 wrote:
Hmm. Ours has an intake and outlet to the outside world - but it also has
a small shoebox-sized pump beside it, which collects moisture and pumps
it into the waste water system for the house. I'm not sure if that pump
is for extracting moisture that's in the air, or from the gas supply -
but given the way it's floor mounted beside the furnace it looks like
optional extra equipment, as otherwise surely it'd be built into the
If it *is* optional on furnaces and the OP doesn't have it, maybe they
need it, whatever its exact function is...
(just idle speculation, not based on any knowledge of how furnaces work! :-)
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