Window condensation

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Startled Cat
Posts: 372
Joined: Thu Apr 03, 2008 8:54 pm

Window condensation

Post by Startled Cat » Sat Dec 01, 2018 2:07 pm

I recently bought a condo and moved in, and I'm very excited to finally have my dream home. So far there has only been one major issue, and I could use some advice for dealing with it. Often when I wake up in the morning, I find large amounts of condensation on the bedroom windows and metal window frames. It's sometimes enough to drip down and pool on the windowsills, and then drip down the walls from there. I'm concerned about damage from the water, so I'm looking for a good solution. This mostly affects the master bedroom, but now that I'm paying attention to the windows, I've noticed small amounts of condensation on some other windows in the morning.

Researching this online has taught me that this happens when there's a lot of indoor humidity, and the windows cool below the dew point. I've found suggestions to reduce humidity with a dehumidifier, or heat the interior more aggressively to raise the temperature of the windows and avoid condensation. I bought a hygrometer and started tracking the humidity in the bedroom. It has been showing about 68% relative humidity, which is apparently quite high. I first thought that humidity was building up inside from showering, cooking, etc., but opening windows doesn't seem to help much. I think the humidity is about the same level outside, and there isn't much I can do to get below that level without actively dehumidifying. Other areas in the home show about the same level of humidity.

I'm in a very moderate climate (Bay Area) and tend not to use heating very much, which I think contributes to the problem. Also, I installed heavy curtains in the bedroom to block light, and I think those are insulating the windows and allowing them to maintain a much colder temperature than the ambient indoor air. Note that the windows are double-paned, but the inside surfaces still get quite cold overnight. I tried heating the bedroom, and so far that seems to have helped a bit. There was some condensation on the metal window frames in the morning, but the actual windows themselves were clear. This might be one approach to solving the problem, I'm not sure yet that it's effective enough. Also, I only have electric heating in the bedroom, so I expect it will be quite expensive to maintain a higher than usual temperature there overnight. Most of the online resources I've found seem to be oriented at cold climates (Midwest and North East), where it's assumed that indoor areas will be heated a lot during the winter.

The other approach would be to run a dehumidifier inside the bedroom overnight. I expect this would be effective. However I'm not thrilled about having something noisy running every night during the cold season. Dehumidifiers seem to need a lot of attention (constantly emptying the reservoir) and online reviews lead me to believe they don't last long. They also use a lot of energy, though not as much as space heaters. In case I go this route, does anyone know of a dehumidifer that is reliable and as quiet as possible? In addition to the compressor and fan noise, many models seem to beep when the reservoir fills up, which would be unwelcome in the middle of the night.

Does anyone have experience with this problem? Would you recommend running a dehumidifier in the bedroom, or taking some other approach like keeping the bedroom warmer at night, or heating the windows directly somehow?

sport
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Location: Cleveland, OH

Re: Window condensation

Post by sport » Sat Dec 01, 2018 2:25 pm

We have the same problem, and solved it. We have double paned windows too. We have pleated blinds on the windows. If we lower the blinds all the way down to touch the sill, there is no circulation over the glass and condensate forms. However, if we leave the blinds up about an inch, or so, from the sill, the air can circulate behind the blind and the windows stay dry. Instead of heavy drapes for room darkening, we use a pleated shade that is coated with an opaque material that completely blocks light. Our weather can get very cold in the winter, much colder than yours. So, if it works for us, it should work for you.

ralph124cf
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Re: Window condensation

Post by ralph124cf » Sat Dec 01, 2018 4:22 pm

Many dehumidifiers have a drain option. If your bedroom is connected to a bath, you could put the dehumidifier in the bathtub or shower, or on a stand and let it drain into the sink. A hose would be required.

A humidifier IS, in fact, a space heater, with the additional benefit of reducing humidity. The exhaust of the dehumidifier is substantially warmer than the intake air.

Ralph

ViperAttacks
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Joined: Mon Aug 20, 2007 2:41 pm

Re: Window condensation

Post by ViperAttacks » Sat Dec 01, 2018 4:28 pm

sport wrote:
Sat Dec 01, 2018 2:25 pm
We have the same problem, and solved it. We have double paned windows too. We have pleated blinds on the windows. If we lower the blinds all the way down to touch the sill, there is no circulation over the glass and condensate forms. However, if we leave the blinds up about an inch, or so, from the sill, the air can circulate behind the blind and the windows stay dry. Instead of heavy drapes for room darkening, we use a pleated shade that is coated with an opaque material that completely blocks light. Our weather can get very cold in the winter, much colder than yours. So, if it works for us, it should work for you.
:thumbsup

This simple solution also solved our problem after I spent a massive amount of time trying to figure it out! For our case, I thought the windows were leaking due to rain (or outside condensation) so I spent an enormous amount of time sealing up all the windows myself.

Startled Cat
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Re: Window condensation

Post by Startled Cat » Sun Dec 02, 2018 12:14 am

sport wrote:
Sat Dec 01, 2018 2:25 pm
We have the same problem, and solved it. We have double paned windows too. We have pleated blinds on the windows. If we lower the blinds all the way down to touch the sill, there is no circulation over the glass and condensate forms. However, if we leave the blinds up about an inch, or so, from the sill, the air can circulate behind the blind and the windows stay dry. Instead of heavy drapes for room darkening, we use a pleated shade that is coated with an opaque material that completely blocks light. Our weather can get very cold in the winter, much colder than yours. So, if it works for us, it should work for you.
This is good advice. I started doing this recently and I think it helps, but I still have condensation forming on the windows, especially their metal frames.

As you say, my winter weather is not especially cold. So it's very strange to me that I'm having this problem and it's a lot more stubborn than it was for you.

I'm a little worried about what to do when I travel. At least when I'm home I can keep an eye on things and put fresh towels on windowsills to catch the moisture. If the long-term solution is to run a dehumidifier, I don't think that's something that can safely be done unattended for days or weeks (even with a drain hose). Similarly, I wouldn't want to run an electric heater while I'm out of town.

sport
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Joined: Tue Feb 27, 2007 3:26 pm
Location: Cleveland, OH

Re: Window condensation

Post by sport » Sun Dec 02, 2018 12:22 am

Startled Cat wrote:
Sun Dec 02, 2018 12:14 am
As you say, my winter weather is not especially cold. So it's very strange to me that I'm having this problem and it's a lot more stubborn than it was for you.
We have wooden frames.

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sergeant
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Re: Window condensation

Post by sergeant » Sun Dec 02, 2018 12:29 am

Startled Cat wrote:
Sun Dec 02, 2018 12:14 am
sport wrote:
Sat Dec 01, 2018 2:25 pm
We have the same problem, and solved it. We have double paned windows too. We have pleated blinds on the windows. If we lower the blinds all the way down to touch the sill, there is no circulation over the glass and condensate forms. However, if we leave the blinds up about an inch, or so, from the sill, the air can circulate behind the blind and the windows stay dry. Instead of heavy drapes for room darkening, we use a pleated shade that is coated with an opaque material that completely blocks light. Our weather can get very cold in the winter, much colder than yours. So, if it works for us, it should work for you.
This is good advice. I started doing this recently and I think it helps, but I still have condensation forming on the windows, especially their metal frames.

As you say, my winter weather is not especially cold. So it's very strange to me that I'm having this problem and it's a lot more stubborn than it was for you.

I'm a little worried about what to do when I travel. At least when I'm home I can keep an eye on things and put fresh towels on windowsills to catch the moisture. If the long-term solution is to run a dehumidifier, I don't think that's something that can safely be done unattended for days or weeks (even with a drain hose). Similarly, I wouldn't want to run an electric heater while I'm out of town.
It is absolutely safe to run a dehumidifier for weeks and months as long as it has a place to drain. My relatives run them all year long in their basements on the east coast. They go unchecked for months at their vacation homes on the Cape.
Lincoln 3 EOW!

CedarWaxWing
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Joined: Sun Nov 02, 2014 12:24 pm

Re: Window condensation

Post by CedarWaxWing » Sun Dec 02, 2018 12:35 am

https://www.builditsolar.com/Projects/C ... lewrap.htm

Put bubble wrap on the windows for a winter insulation. Saves heat, I think it should also prevent the condensation.

After that, don't pull the blinds down...

Good luck.

OnTrack
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Joined: Wed Jan 20, 2016 11:16 pm

Re: Window condensation

Post by OnTrack » Sun Dec 02, 2018 1:11 am

Do you have a basement, slab or crawl space? If a crawl space, what is the floor of the crawl space? If it is soil or gravel, I have heard that a layer of plastic sheeting can help if not already present. I'm not an expert though, so consult with the appropriate professional.

I agree with the discussion above about making sure that the window coverings do no restrict air movement to the glass surface of the window. Also, the extra cost of raising the heat a few degrees is probably minor compared with the potential cost of repairing moisture damage or mold.

68% as you say is very high. I read somewhere that it should be no higher than 50% and lower depending on the outside temperature.

Since this is a condo, have you asked neighbors if they have the same problem and if so have they found a solution? Also, is it possible that there is some condition in a neighboring unit that is contributing to the high humidity (might be difficult to find out though)?
Last edited by OnTrack on Sun Dec 02, 2018 1:37 am, edited 1 time in total.

longleaf
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Joined: Sun Nov 26, 2017 4:13 pm

Re: Window condensation

Post by longleaf » Sun Dec 02, 2018 1:26 am

It is SF bay area, that's the contributor of the humidity.

Run a dehumidifier that drains automatically
Frugality, indexing, time.

mountainsoft
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Joined: Mon Jan 25, 2016 12:39 pm

Re: Window condensation

Post by mountainsoft » Sun Dec 02, 2018 1:37 am

Startled Cat wrote:
Sat Dec 01, 2018 2:07 pm
Often when I wake up in the morning, I find large amounts of condensation on the bedroom windows and metal window frames.
Your first task should be to minimize the amount of moisture in your home. Some humidity is normal, but most indoor moisture comes from showering, cooking, laundry, or moisture coming up from the ground. Opening a window can help but without a cross flow breeze the moisture is going to remain in the house. You really need to use exhaust fans when showering, cooking, or doing laundry and let them run several minutes after you are done to remove residual moisture. Keep in mind you'll need a way to let fresh air enter the home as the humid air is exhausted. Older homes usually leak enough air that it's not an issue, but you may need to open a window on the opposite end of the house if you have a tight house with no other fresh air inlets.

You should have a plastic vapor barrier on the ground in your crawlspace, or under the concrete slab in a basement or slab on grade (Tape a piece of plastic to your concrete floor overnight. If you see moisture under the plastic in the morning, you have moisture coming up from the ground). Make sure your clothes dryer and bathroom fans vent outdoors and not in the house, attic, or crawlspace.

Metal window frames conduct heat better than vinyl or wood windows. So you will usually get more condensation with metal windows. Adding storm windows on the exterior of the home, or even applying those shrink wrap films over the windows can help reduce the heat transfer and reduce condensation. Installing new double or triple pane insulated windows is even better.

Adding a dehumidifier is another option, but shouldn't be necessary if you have proper ventilation and minimize the moisture at the source.

Condensation leads to rot and mold. Best to solve it as soon as possible.

oldlongbeard
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Joined: Tue Oct 23, 2018 11:07 am

Re: Window condensation

Post by oldlongbeard » Sun Dec 02, 2018 6:40 am

A ceiling fan running on low in your MBR 24/7 can make a dramatic difference. The aluminum frames are 99% of the reason for the condensation. It’s just physics.
I live in the Mitten......our homes are DRY in the winter as the forced air heat, and dry outside air are a double-whammy. The builder-grade windows used here kinda suck. Sure would like quality replacements, but GOOD ones are very expensive.

Kind regards,
Greg in West Mitten

Startled Cat
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Joined: Thu Apr 03, 2008 8:54 pm

Re: Window condensation

Post by Startled Cat » Sun Dec 02, 2018 4:18 pm

Thanks for all the tips!

A quick update: There was a lot of condensation last night (not surprising since it was a relatively cold night). This was despite running the heat more than I normally would and avoiding closing any pleated blinds completely. The master bedroom was the worst affected, as always, but I saw condensation on many of the window frames throughout the home.

This morning, I tried opening most of the windows for ventilation. Initially I though there would be no point, since the relative humidity was 71% outside - even higher than the 66% I was reading inside. But I did the math on how this translates to actual moisture levels given the temperatures involved, and found the outside air had 6.4 g/m^3 of moisture, vs. 9.6 g/m^3 on the inside. Thus ventilation should help clear moisture.

I've had the windows open for the last few hours, and the interior humidity has dropped to 50%. It seems like it's working - I'm eager to see if the humidity level stays low through the night. My current working theory is that a few weeks of showers, cooking, and laundry have built up moisture that has nowhere to go, because smoke from the fires followed immediately by rainy weather had me keeping the windows closed. It seems like opening the windows for ventilation helps even if the relative humidity level is higher outside, because the colder outdoor air actually contains less moisture.

If all this is correct, hopefully there won't be any problems when I go out of town as long as I get the humidity level down before I go. If there are no significant sources of moisture inside while the home is unoccupied, ideally the humidity level will stay for days or weeks and there won't be any problems with condenstaion.

I also ordered a dehumidifier, which should be a more comfortable and energy-efficient option than opening many windows in this cold weather. I might order a second one if necessary, since I have two stories and high ceilings, meaning there's a lot of air volume to dehumidify.

mchop
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Re: Window condensation

Post by mchop » Wed Dec 05, 2018 2:29 pm

Please update with any further details

New home in Seattle and have the same scenario. Been running a dehumidifier for 3 weeks with varying results

Thanks

MnD
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Joined: Mon Jan 14, 2008 12:41 pm

Re: Window condensation

Post by MnD » Thu Dec 06, 2018 10:21 am

Good advice on managing the humidity that's already in your living unit but as other have mentioned, what's under your condo? If its a dirt crawlspace and the there is no vapor barrier you likely have a chimney effect drawing an unlimited supply of soil water vapor from the soil into the living unit. This is easily fixable with encapsulating the crawl space floor with a high quality vapor barrier product and proper installation. If it's a slab or a concrete basement floor, hopefully they put a vapor barrier under the concrete when the poured it.

I had water dripping down windows (and frost in the attic!) and installing the vapor barrier fixed everything immediately and permanently.

Startled Cat
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Joined: Thu Apr 03, 2008 8:54 pm

Re: Window condensation

Post by Startled Cat » Sun Dec 09, 2018 12:58 pm

Unfortunately, ventilating the home daily and running a dehumidifier hasn't been enough to fully solve the problem. I can bring the humidity down to 47% or so in the bedroom in the late evening, and then turn off the dehumidifier to sleep. By morning, the humdity will be back up to 60% or even higher. This is high enough for water to condense on the metal window frames, even when the indoor temperature is relatively warm. I see this condensation on other window frames in other rooms, but usually only certain windows (some seem to be immune from the problem). This does represent progress, since before certain windows were sometimes getting fully covered with moisuture, and that was the main source of the dripping. But having daily condensation on inner window frames still seems like a problem that needs to be solved.

One mystery to me is why the indoor humidity level climbs when there shouldn't be any sources of moisture. I can open windows to ventilate the unit in the morning, then go to work and come back to 5-10% higher humidity, even though no one has been home. The humidity level also consistently climbs overnight. The moisture may be coming from the outside air (outdoor humidity is reported at 94% as I write this), but if so, why does opening the windows usually help? I'm beginning to suspect that there may be a leak somewhere contributing to the problem, but on the other hand it would be surprising to have enough water leaking in to raise the humidity, but not see any other evidence of it. Some people have mentioned the possibility of moisture rising from the ground, but I don't think that's the issue. I'm on the top floor and have another two-level condo below me. Below that condo, there's an underground parking garage.

I do know that this unit had an issue with water intrusion in the past (I found this out from a neighbor after moving in). The building recently finished a major waterproofing project which was supposed to have fixed the related problems.

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