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Bathroom Window Condensation = Bad


TorontoJoe's Avatar
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11-13-13, 07:01 AM   #1  
Bathroom Window Condensation = Bad

Recently moved in to a 50 year old house with windows that appear to have been upgraded...But not recently. The existing window in the main bathroom is one of these unsealed, triple-pane deals.

The window is not in the shower but being that this is the room where all the showers happen there's some moisture in the air.

Since the colder weather has come and I've begun heating (forced air gas), I've noticed a lot of condensation building up on the exterior pane.

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Now, on it's own I really don't care that there's some water building up. My concern is that of mold. I'm worried that with the windows closed up all the time, and with all the moisture and light, that I'll be getting mold growth in there...And perhaps other water damage.

There is a good exhaust fan in the room already.

Might anyone have any advice that might:

-Help to reduce or eliminate the condensation build up?

-Just prevent the growth of mold?

I was thinking of periodically putting some alcohol in a spray bottle and spritzing the area. That would likely kill any mold growth but it would still be wet and perhaps create some other issues that I haven't thought of as yet

Thanks all.

 
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11-13-13, 07:19 AM   #2  
Just curious, but how long are people using the fan after they have a shower?

Lots of people turn it off once they leave the bathroom after a shower. It should run for around 20 minutes after you're done.

 
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11-13-13, 07:28 AM   #3  
I have it on a timer and let it go for 60 minutes actually

I should also probably mention that the gas furnace is equipped with a humidifier. Its currently set to 40%

There are other windows in the house of this same style that show the same sort of condensation, just not as much.

In all cases it only occurs on the inside of the outer most window.

 
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11-13-13, 07:46 AM   #4  
I'd get another humidly gauge and check the air.
With that much humidity showing there's no need to run it.

 
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11-13-13, 07:58 AM   #5  
Good idea.

That being said...I can completely dry it out and close up the windows. Again, the moisture builds up on the outside, where its in theory more dry. On the inside where it's warmer and apparently more humid, it's dry.

 
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11-13-13, 10:16 AM   #6  
Sounds to me like the bath fan exhaust must be too close to the window. why else would the outside get so wet? Where is the exhaust outlet located?

 
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11-13-13, 10:43 AM   #7  
Smashing idea. I have no idea where it is. I'm not home at the moment but when I am I'll check it out.

Thanks. I'll let you know

 
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11-13-13, 04:08 PM   #8  
Sorry, was reading your post on my cell phone and couldn't see the pictures very well.

I can see now that the condensation is all on the interior side of the outer storm window. This will usually happen when the interior window is very leaky, and the exterior window is caulked tight... allowing a lot of warm humid air out past the first set of windows where it then condenses on the cold surface of the outer windows.

Not being able to examine the window, it's hard to say what a solution might be. The exterior storm window should probably not be caulked completely shut. there are often weep holes or a sill expander on the bottom that should be left uncaulked so that liquid moisture can escape as needed. This space also allows fresh air in which allows just enough air exchange that it prevents the humidity from getting too high and condensing.

As far as cleaning the windows, I'd suggest you use some Tilex to clean the window and it's parts... using a toothbrush if you need to get into cracks and such. Mold really will not form on glass or aluminum if you have kept it clean. It will form on wood and under paint, so keeping the wood dry is important. But provided you wash the window a couple times a year I don't think mold will be a problem on it.

While you have the sashes out to clean them, pay special attention to the pile weatherstrip on the perimeters of the sashes. (look for weatherstrip in the frame too. Lightly scrub the weatherstrip with a bristle brush and detergent. If the weatherstrip has become packed with dirt it won't be real effective at stopping air as it's all smashed down. Scrubbing it may just fluff it up enough that the window may seal better after you put it all back together.

If any of the weatherstrip is damaged or missing then that is likely the reason your exterior window is so wet. It's because the inner window isn't sealing very good. Air pressure (wind blowing from the opposite side of the house) is forcing warm humid air right out past the edges of your interior window sashes.

 
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11-13-13, 09:12 PM   #9  
Hey Thanks. The outer window isn't calked and does open and close but I'll have to check on the weep holes in the morning when I have a bit of light to really check things.

These windows aren't exactly sealed tight to I'm starting to see what you mean about the warm air going out to the outer window.

I'm thinking I might dry out that outer window as best I can and perhaps seal it off for the winter with some of that window shrink wrap stuff. Then next year I can look at my options for a window that actually seals shut....At least for this bathroom.

If indeed the lack of a really good seal is the culprit, then nothing I do will be any mote than a temporary solution. And if the moisture is not really a problem in that area of aluminum and glass then my real problem is that money is seeping through the gaps that's allowing the warm air out...

It's a pain - I just replaced 5 windows on the entire front of the house. I was hoping these ones could last a while. I wish there were a way to test an older windows efficiency....

 
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11-13-13, 09:20 PM   #10  
One More Thing

I forgot to point this out...The previous owner as you can see here painted over some mold that build up on the inside. I'm trying to decide if it built up on the inside due to the problem that we've been discussing, or if perhaps there's some other leak....The inside is dry now however and it seems like a strange place for mold to grow given that this area does dry up and is open.

thoughts?

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11-14-13, 04:36 AM   #11  
It probably indicates that water is getting into the wall somehow... either from the window condensation leaking through the frame of the window or on the outside around the window via the siding. If air can pass around the trim, it could be condensation within the wall too... condensing on cold wood just like it does on your cold glass. Aluminum window frames are notoriously leaky where the side of the frame joins to the bottom of the frame, so water could be leaking out this joint around the frame of your window. You'll find out for sure if you ever tear out and replace that window.

If it's not punky, you can cover the stain with B-I-N or Perma White or similar stain blocker. But if the mold beneath the paint is getting worse and continues to grow then it obviously it has the requirements for mold growth (food and moisture) then it will just continue to reappear.

 
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11-14-13, 07:28 AM   #12  
Sigh....I think its time to do some probing.

 
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11-17-13, 12:17 PM   #13  
Condensation on cold bathroom window.

It only makes sense to write about “Humidity” when you include the temperature at the moment.

We always write about “Relative Humidity” and from the example below you can see that a humidity of 44% can mean anything, without the relevant temperature.

I would guess that the temperature in your bathroom, at the end of a shower will be in the region of 80 degrees Fahrenheit and that the relative humidity will be about 75%.

If you look below you will see that this gives you a “Dew Point” of 71 degrees Fahrenheit, that means that nearly all the water vapor in the room will head for the coldest surface – the inner surface of the outer most window, on anything other than a warm day/night.

As you have triple windows, the idea is, that each of the windows should be a water vapor tight fit in its frame, with each window and air gap the room side surface temperature of the window will rise, taking the room side of the inner most window above “Dew Point” and transferring the water vapor/condensation elsewhere. ( Hopefully out through the exhaust fan.)

Condensation forming on clean glass does not lead to mold. Mold only forms where there is both food and water. While you have plenty of water in the form of condensation, you do not have any food for the mold to feed on as long as the windows are clean.





Dew Point Calculation Chart (Fahrenheit)
%RH AMBIENT AIR TEMPERATURE IN FAHRENHEIT
20 30 40 50 60(70)80 90 100 110 120
90 18 28 37 47 57 67 77 87 97 107 117
85 17 26 36 45 55 65 75 84 95 104 113
80 16 25 34 44 54 63 73 82 93 102 110
75 15 24 33 42 52 62 71 80 91 100 108
70 13 22 31 40 50 60 68 78 88 96 105
65 12 20 29 38 47(57)66 76 85 93 103
60 11 19 27 36 45 55 64 73 83 92 101
55 9 17 25 34 43 53 61 70 80 89 98
50 6 15 23 31 40 50 59 67 77 86 94
45 4 13 21 29 37 47 56 64 73 82 91
40 1 11 18 26 35 43 52 61 69 78 87
35 -2 8 16 23 31 40 48 57 65 74 83
30 -6 4 13 20 28 36 44 52 61 69 * 77
At Sea Level (14.696 psiA)

 
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11-17-13, 07:12 PM   #14  
Being Canadian I have no concept of Fahrenheit so I had to make the conversions for myself first.

OK - So basically in plain language, even with the existence of this moisture there is no real concern of mold unless the water is getting outside the window unit, which is aluminum and glass, correct?

So this is what I need to confirm.

I suppose a secondary concern is that the warm air is so easily making its way to that exterior window. It makes me wonder how much it's costing me in lost heat....Hmmmm

 
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11-18-13, 04:10 AM   #15  
Condensation on window.

The whole point of having treble glazing/windows is to keep the heat in the bathroom. Each piece of glass followed by an air space, helps to keep the room warmer. When triple windows are used and fitted properly, you don't get any condensation.

The greater the difference between the temperature of the room side of the outside window and the indoor air temperature the greater the heat loss, the more it costs you to keep warm. Having, outer glass then an air space, middle glass air space, room side glass makes an enormous difference to the comfort in a home.

I have fitted quad glazing/windows in my home, that's two lots of double pane windows separated by a four inch air gap, ( the four inch gap is to allow the fitting of venetian blinds inside the windows to keep the sun and heat out in summer) when it is -18C outside the temperature in the center of the room side of the glass is 22C that's with a room air temperature of 22C the walls and ceilings are also 22C the floor is between 24 and 27C.

The most effective space between sheets of glass is 19mm. If the gap is larger than 19mm the air can start to rotate and transfer heat from one piece of glass to the other.

 
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11-18-13, 04:35 AM   #16  
I've never heard of someone "quad-glazing" before. I'd love to see a few pictures if you're able to post them here.

 
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11-18-13, 05:47 AM   #17  
The windows in question all look like single pane glass to me... maybe the op can tell us. At any rate, an aluminum frame window is not the best kind for a cold climate like Canada.

 
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11-22-13, 04:20 AM   #18  
As requested

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As you can see, just ordinary windows. The one's with the venetian blinds are facing south, the one with flowers between the windows face north.

 
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11-23-13, 06:06 AM   #19  
Good pics.

Your windows look European, or at least Euro extrusions. Can I ask who is the manufacturer? Are they tilt/turn?

Also, does the dual window come from the manufacturer or was this a custom set up by the builder/installer?

You, and perhaps others, may find this link interesting. I am not endorsing in any way. Good pics. Exclusive: Deceuninck North America Genius Window System - YouTube

Thanks

 
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11-23-13, 07:00 PM   #20  
Perry - That's very impressive. So you basically used two sets of double glazed....Both casement-fixed-casement. Hard to tell. Did you just get them without any mold, sit them at the interior and exterior edge of the frame and just trim around?

It looks really good. I was considering triple glazed for a window I need to replace in the front of my house but this has inspired me.

Question - How thick are your walls? they seem pretty deep. Mine are basically the exterior brick, insulated stick frame and drywall...So about 8" I think.....

Thanks for the pic's

 
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11-24-13, 01:09 PM   #21  
The existing window in the main bathroom is one of these unsealed, triple-pane deals.
For Pete's sake -- don't call them that.
Call them *aluminum sliders* , *single pane sliders* but don't call the triple panes -- You give a true triple pane windows a bad rap.

Seriously though --- those are common old style replacements to original wood frame single pane windows that started around the late '60's into late 70's.
At the time they touted as being a better alternative to the original windows --- aluminum versus wood ( no rot or maintenance ) and actually did have *some* thermal improvement to the old originals.
The thermal improvement came from the increased air space between layers of glass -- in your case 3 layers. When they would have been first installed they were probably not that bad ( nowhere near today's standard ) providing they were properly installed to begin with.

However , over time as the weather seal between sliders wore down the air seal between sections was weakened leaking warm moist air from the inside of the home outward causing frost buildup ( when cold enough ) or condensation ( sweating ).

The other pitfall -- the aluminum while nice for not rotting and pretty much zero maintenance -- unfortunately they easily allow heat transfer and for our cold climate that's not good.

The attached photos show a very similar window in a bath/shower location.
When I took this photo this morning, it was 22 below zero and you see no condensation or frost.

The main reason is there is a plastic film covering the inside portion. This from one of those window film kits with double sided tape and use the hair dryer to take out the wrinkles. These do work and are relatively inexpensive.
You might try one.

Also, on the topic of humidity and condensation here's a link to see the correlation
Dew Point Calculator

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11-25-13, 07:13 AM   #22  
For sure. These things were installed in a time when heating energy was cheap. I'm sure it's for this same reason that there's about 5" of insulation in my attic - That was what the original builder put in. Have to remedy that this week.

I did pick up a few of these film kits to get me through the winter. It's not a huge insulator but I figure it's at least a bit of a vapor barrier.

Next year I'm going to have to be shelling out for some new windows .... cha-ching...sigh...

 
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