Hello- New member, first post. I started building cabins/small houses in the far north of Wisconsin a couple years ago. Before that, I had never built a house before. So far, I’ve been using vinyl windows, mostly double-hung, but also a few picture windows. Got the windows through Home Depot. Having a problem with moisture building up on the inside face of the glass, in a horizontal band along the bottom inch or two of the glass in each sash. A little moisture builds up on the vinyl too, at least on the bottom sash. The moisture only builds up when the temp outside gets down to 10 degrees or so. On mornings like today, when the temp is 16 below zero, the moisture turns to ice at the very bottom of the moist band. My cabins are entirely lumber, with floors, walls, ceilings all made from t&g pine. Since I’ve been at this only a couple years, I don’t know if the problem eventually goes away as all this wood dries out. I recently bought four hygrometers in order to get an idea of what the humidity level is inside, thinking that it might be a problem of excess humidity. I’m not sure how accurate the hygrometers are, and plan to take them somewhere to check them against a better hygrometer known to be accurately calibrated. In the meantime, I believe the humidity level to be quite low, since I run fans and dehumidifiers almost constantly, and live alone, producing very little moisture from showering, cooking, etc. The hygrometers read from 42 to 57 % depending on how warm the room is. The humidity reading on the dehumidifier reads as low as 21%, but I don’t know yet if that is reliable; will know more once I’ve checked the accuracy of the other hygrometers. The windows are expensive, as vinyl goes. The glass is 3/4 inch, with the low e coating, but without the optional argon gas filling, which the Home Depot clerk advised against, saying it would just leak out anyway. For what it’s worth, the two picture windows on the most recent cabin sweat worse than the double hungs, which of course are much more drafty.
Any ideas what could be going on? Being new to the building trade, I don’t know how various window types perform in the cold. I assume a storm window would solve the problem, but have been told that vinyl windows can’t be used with storms because they would warp under the buildup of excess heat trapped by the storm. Are vinyl windows not intended for cold climates? Would I be better off with clad windows? My type of construction (post and beam, with rigid foam insulation on the outside) requires a nailing fin. The picture windows have weep holes along the bottom on the outside face of the frame, but any moisture trying to get out the weep hole in the winter would freeze and clog the hole.
Any thoughts would be appreciated.
Replies
My guess is that the problem is not with the windows themselves and that this would happen with most windows in your case. What is under the floor? Could moisture be coming from a damp crawlspace or basement? This would need correcting. Or, maybe your posts and beams are releasing more water than you think. In that case, the problem may go away on its own.
Al Mollitor, Sharon MA
I've had the same problem in each of my last two cabins. One cabin is on a slab on 5 foot deep frost walls. Beneath the slab is a layer of 6 mil plastic under a layer of insultarp. Heat tubes in slab. The other cabin has a full basement with a layer of 6 mil plastic and a layer of inch and a half pink rigid foam. Also with heat tubes. A hygrometer in the basement shows the humidity to be the same as one of the cooler rooms upstairs. Again, these are $10 hygrometers, and I'm not sure they're at all accurate. I will know more when I compare them to a properly regulated hygrometer, which I plan to do soon. I run fans and dehumidifiers a lot, and the slab cabin is unoccupied, so little additional moisture is being introduced. You may be right about the wood still giving off moisture. There's an awful lot of wood, and it's all still pretty fresh, with the basement cabin being just over a year old, and the other just being finished.
In the past we have replaced wood windows which have turned black and started to rot in new post and beam homes that have styro-panel insulation. These windows would be dripping water in the winter time. There were two ways we fixed the problem. Styro foam insulation, especially on a cathedral roof, if not vented properly, holds in a large amount of moisture in the house. Solution - a properly installed air exchanger or HRV. Second, we made sure there was adequate forced air or radiant heaters under all windows (this helps dry the windows during cold days). We also made sure that there humidifier was either off or set very low. This seemed to solve the problem with no call-backs.
Just one more thought. Vinyl wndows aren't the problem in these cold climates. Our company has been installing vinyl windows here in the Toronto area for 15 years with-out any major problems. When there have been problems we found it is usually the air quality in the home.
Thanks for the ideas. I hate to parade my ignorance, but what is an air exchanger and same question for an HRV? Or if it's too involved, should I talk to a heating contractor? My cabins don't have forced air, so you might be on to something. The heat comes from a boiler heating the slab tubes (propane), and from cast iron propane stoves (fireplace style). Thanks again for the input.
Are the cast iron propane stoves vented?
If theyare ventless.....there is your extra water vapor input into the cabin.
40% humidity is way too much for the temps you have quoted...there is no choice but to have condensation on those cold glass surfaces.
..................Iron Helix
An air exchanger or HRV (heat recovery ventilator) exchanges the stale, moist air from the rooms that would cause the most humidity eg. washrooms and kitchens. It would be wired into a timer to exchange the air in the home at least once a day or more depending on the number of occupants and the amount of humidity produced in the home. The unit allows the exhausted air to pass beside but not mix with the fresh air being drawn into the home. This allows the warm exhausted air to warm the cold intake air, but different units have different efficiency ratings. It is best to talk to your local heating contractor and compare at least three different models.
I appreciate the lesson. I have a heating guy coming out tomorrow to talk to me about air exchangers and another will be quoting me a price. The first guy guessed about $1800 for the job, parts and labor. The propane stoves are all vented to the outside. Thanks for the info.