Thanks to all who replied, I'll try to address your comments and fill in the
blanks I left.
The house is in central Connecticut. It is on the North slope of a hill.
When we moved in, much of the house (including some of the windows that
wouldn't hold paint) was in perpetual shade; the neighbors' yards were full
of pine trees much taller than our houses, and there were trees and
overgrown shrubs up against the house. We've all done significant cleanup
since then, so the house gets more sunlight now. There is actually algae
growth on some of the siding where the sun never shines, even now.
I suspect that there is an underground water flow down the rock ledge that
forms the slope: our back yard tends to stay squishy, despite being on a
hillside, until midsummer. The yard slopes past the house.
I have no idea what is under the siding. When they built the house, they
probably did try to button it up tight; at least, I'm guessing that's why
the attic had almost no venting. There was blown-in insulation in the attic,
whether they tried to stuff it into the walls or not I don't know. I added
two layers of blanket insulation when we shingled the roof and added all of
the attic vents.
I realize that running a humidifier and a dehumidifier at the same time
sounds silly, but the basement is so much more damp than the rest of the
house that it seems necessary. Even with the furnace-based humidifier going,
you can still get a decent spark walking across the carpet in winter. Our
hygrometers are digital; they may or may not be accurate, but the one in the
basement generally reads 35%-40% and the one upstairs generally reads more
like 25% in cold weather. Remember that the humidifier only runs when the
heat does, so what it really does is mitigate the dryness of the hot air
coming from the furnace.
Speaking of the furnace, the house temperature doesn't fluctuate much in the
room where the thermostat is. Obviously a house this big and with this floor
plan would be better off with multiple zones. There is no real return in the
basement (other than the access door of the furnace), but there is an outlet
that is left open in heating season.
We don't have any carbon monoxide problems. The furnace and hot water heater
vent up a chimney.
The laundry appliances are in the kitchen, which has never had a visible
condensation problem; it is one of the few spots on the ground floor that
gets any sunlight, so that might be why. We replaced the kitchen window not
long ago for looks, but it was in pretty good shape so far as I recall.
The dryer vents directly to the outside; so does the fan in the downstairs
lavatory, but it gets used rarely and I don't see any signs of moisture in
that lavatory. Whoever installed the fan in the windowless upstairs bathroom
was a moron; originally, the fan simply vented directly into the attic. I
added the fan in the master bath (which has a window), and ran the exhaust
to as close to the vented soffits as I could get. I'm not personally skilled
enough to put in a roof vent; that would be an obvious step the next time we
have work done, but at the time I figured running them out into the eaves
was a heck of a lot better than letting the moisture accumulate in the
The master bath, and adjoining bedroom, are really the only rooms where
there is noticeable moisture on the inside of the windows. The other windows
with obvious problems are the ground floor casements, which are shaded
(North side of the house, and shaded by the neighbor's pines). Their
construction is part of the problem: they are single glazed with a removable
second pane (inside). This was obviously an attempt to make them their own
storm windows, but since the inner panes aren't sealed you get moisture
condensing between the two panes. That may be the bulk of the problem.
The basement is damp in the summer and (to a lesser degree) in the winter.
The condensation problem I'm talking about is a winter problem.
The master bath is a problem, period, because that's where my wife and I
take showers in the morning. Since the heat goes off for the day shortly
afterwards, I rely on the exhaust fan to clear it out; but an hour later,
there's still sweat on the toilet tank (even if I leave the fan running).
The fan does move some air, but perhaps just not enough.
The first floor casement windows are probably a victim of their
construction, and nothing will do for them but replacing them with properly
double-glazed ones. That, and fixing the bathroom fans to exhaust to the
outside (and maybe putting in a larger one), would probably take care of the
bulk of the problems.
The more I try to explain this, the more I suspect that we might have
already mitigated much of the problem. I'd like to find someone who can take
an objective look at the situation, so I don't put in new windows only to
have them rot away.
I just hope that when the siding is eventually replaced, they find intact
studs not rot.
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