I’m having a condensation problem on the windows of my 6yr. old house. It’s well insulated (r-19 walls & r-38 ceiling) and a poly vapor barrier on the walls. An energy auditor said the house is almost too tight. I installed an air exchange system as recommended by him. It does 250 cfm, running 10 min.,8 times a day. Exhaust fans in each bathroom are run when bathing and a downdraft fan is used during cooking. I can’t get the humidity below 40% in the house and when the temperature goes below 32 condensation forms around the outside edges of the glass. I’m afraid the sashes willbegin to rot. Anybody got any ideas?
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Do you have a forced air heating system? You could have a cracked heat exchanger and the vapor from the burned gas may be crossing over to the house air side. Call an HVAC specialist.
40% actually sounds pretty good, I struggle to keep mine above 40% even after doing lots of tightening over the years (100 yr old house).
One solution to deal with the almost ineveitable condensation on windows (unless you can get the humidity during severe cold down below a nose-bleed inducing, lifethreateningly-static-shock territory <35%) is to put storms outside your regular windows. The storm window then becomes the main dew-point drop and the condensation forms (harmlessly) on the aluminum framed unit, rather than on the wood framed (and much more expensive) main window unit. I put an aluminum cover on the sill too, so any condensation that runs down won't touch any wood.
One other thought is: is your heat exchanger running often enough? 10 min, 8 times a day sounds like it is hardly ever on (as a point of reference, in the other direction, if you were trying to dehumidify in the summer time with an AC that would never be often enough (cycling) to keep a home dry, I think, even in a very tight home). But I am not an HVAC specialist.
My windows are casements. I don't know if there is any kind of storm available. Also if I run the air exchanger much longer, the house turns into a refrigerator. The house has in-floor radiant heat.
First off Rick, you didn't say what kind of windows you have. Are they single glazing or double pane insulated?? Sounds like you may have single pane if you get condensation forming at only 32 deg. F
What temperature do you maintain indoors during the day and overnight?
I agree with previous post that 40% is pretty good for the winter. Some people run humidifiers to get to that point.
If you have hot water radiant heat, you may want to buy yourself a small hot water booster coil and install it in the air exchanger ductwork so you can gently heat the outside air.
Good luck!
I have a new place...still under construction. Pella double pane insulated windows (Low E, Argon filled). I don't have constant heat on...a woodstove keeps it nice when I'm around to keep the fire going. Boiler is yet to come...not living there...apparently pretty tight. When I open the entry door, I can hear the flappers on the dryver and shower vents flap (not hooked up yet). I see the same condensation, just around the very edge of the windows...preferentially along the bottom. I hope when I get the heat on (in floor radiant) that it will make a difference. I suspect I might need to add some ventilation as well.
I'm hoping with the 1408 sq ft. concrete floor, some big white pines which are drying (every now and then you hear a crackle from them...pretty neat), lots of new sheetrock (I've been told moisture will seap from these the first year), some rough cut drying, etc. When I get the heat on, hopefully my moisture problems will go away.