This is condensation due to relatively high humidity or still air in the
room, and cool temps outside, just as droplets form directly from
surrounding air, on a glass of cold water. Storm windows or double pane
replacement windows will reduce condensation by lessening the temperature
drop across the inner window. Other more frugal measures would be to lower
humidity by increasing air circulation and ventilation inside, through
window-directed fans, open windows, and perhaps, an inside electric
I agree with Nick on this one. Making the house cooler will not help
unless you do it with an air conditioner or dehumidifier to remove some
of the moisture. You want to LOWER the dew point, not raise it.
Getting rid of the moisture source is the best way to lower the dew
point inside the house. Using better windows would also help, by
raising the indoor surface temperature of the windows above the dew
point. You could also put plastic film over the inside or outside of
the windows would also help, as Vaughn & Joseph stated. Raising the
temperature in the house would also help raise the inside surface
temperature of the windows, but that could get quite expensive.
Turn on your exhaust fans before taking a shower or
cooking on the stove. Let them run for a few minutes
after finishing. There are timers just for this purpose
that can replace your standard wall switches.
Don't boil the kettle so long. Don't hang wet clothes
up in the house to dry. Close the bathroom door when
showering. Get better shower curtains. Put a lid on
your pots when cooking and turn the heat down. Make
sure your dryer is vented outside.
Have your furnace checked for heat exchanger leaks.
Make sure you get or have a working CO sensor or get a
professional in to check for carbon monoxide. It can
kill you or make you very sick and you may never know
If the problem is lasting and serious install a heat
exchanger to ventilate your home or at least a
If the basement is really damp try putting a rubber
membrane or mat down on the floor and after a few days
see if it is wet underneath. This can indicate whether
it is seeping through you concrete floor. You may be
built on a swamp or spring.
You get condensation when something is cooler than the dew point for the
humidity in the room.
You can reduce the amount of moisture in the air in the room.(1)
You can make the surfaces warmer. Generally better insulation, more
layers of glass etc. Can you say new insulated windows or storm windows?
BTW Aluminum frames are the worst. The best Aluminum is bad, most of
them are far worse that that.
(1.) Generally making the room cooler will help (humidity does not equal the
amount of moisture, it is the % of the maximum moisture that air at the
measured temperature can hold.) So if you cool the room and do not raise
the humidity number, the air has less moisture and will have a higher dew
point. Lowering the humidity and keeping the temperature the same will also
Of course you disagree nick, what else do you do. So what should he "get
rid of" his showers, cooking, family, plants, pets? No his windows, you
don`t even know if humidity is high, but you say lower it, which I
dought is high since construction I bet is loose with those aluminum
frames, and im sure no tyvek.
As others have pointed out, the problem is that the inside air is cooled
when next to the window and moisture condenses out of the air onto the
You don't mention whether you have double-pane windows, or whatever.
Condensation can be seen as two possible problems. Either there is too much
moisture in the air so the dew point is pretty high, or the inside surfaces
of the glass/frame are so cold that they are below the dew point for even
relatively dry air.
Older aluminum windows had the later problem because aluminum is an
excellent conductor of heat so the inside part of the frame is quite cold
when it's cold outside. Newer ones have a 'thermal break' between the
inside aluminum parts and the outside ones so the inside aluminum frame
doesn't get as cold. You mention ice formation so it sounds to me like that
is your problem, old aluminum windows with no thermal barrier.
The expensive, long-term fix is to replace the windows with newer designs.
But a cheap fix is to go to your favorite dept. store or DIY home center and
look for DIY window treatment plastic. They make a kit of heat-shrinkable
plastic and double-sided tape. You put tape around the inside frame of the
window, put the plastic over it as tight as you can, then use a hot-air gun
(hair dryer works) to shrink the plastic tight/clear. It forms a second
layer of dead air between the plastic and window to act as a storm window.
Will last a winter and save a bundle, and is *cheap*. Do as many windows as
With no moisture source in the house, indoor and outdoor air would have
the same dew point. Minimal moisture from human activities (about 2 gal
per day for a family of 4) wouldn't change this much, for an average US
(224 cfm) air-leaky house.
OTOH, most folks don't like the air that dry in the winter. Some of us
prefer the RH above 30% or so, on a day like today, warming up outside air
(dewpoint 20F) would mean just 14% RH. If the OP is seeing frost forming
occasionally, then the outside temperature must be going below 30F a fair
amount of time (warmed to 71F that's 21% RH).
And adding storm windows (even the plastic I mentioned) will help reduce
heat loss and drafts.
You and Nick are *both**ASSUMING* the humidity level is too high. I'm
merely pointing out that another explanation is the humidity is okay and the
inside of his windows, if they are single pane, with aluminum frames is too
cold. Think about it.
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