Thread: Mold on interior of windows

Any idea what might cause this. The majority of the first and second floor windows were in this condition. House was built in 1993.

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Condensation caused by air leaks keeping the wood wet enough to allow the growth.

Poorly finished wood allows the water to penetrate it making the problem worse.

Originally Posted by mathew stouffer

Any idea what might cause this.

The majority of the first and second floor windows were in this condition

. House was built in 1993.

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They Be Leaking.
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*water intrusion noted at windows A. B. C. with microbial growth present.
contact a license competent window professional for repair / replacement.

Then time to move on.
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Excessive condensation on the glass caused by high humidity in the home due to excessive plants, or people or a whole house humidifier running too high.

Originally Posted by John Dirks Jr

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Condensation caused by air leaks keeping the wood wet enough to allow the growth.

Poorly finished wood allows the water to penetrate it making the problem worse.

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Originally Posted by Ken Rowe

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Excessive condensation on the glass caused by high humidity in the home due to excessive plants, or people or a whole house humidifier running too high.

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This Theory is not supported by the posted picture.

* side window frame with downward streak does not match staining / damage of window frame to support condensation induced damage.
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** John if air can come in can't water ?

*** if Cold Air Leaks Meet Humid Conditioned Air and produces water at what point on the window casement does this happen ? Is it All the way In The Conditioned space or Does The Water Form outside the window seal outside of the conditioned space ?

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Originally Posted by Billy Stephens

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This Theory is not supported by the posted picture.

* side window frame with downward streak does not match staining / damage of window frame to support condensation induced damage.
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** John if air can come in can't water ?

*** if Cold Air Leaks Meet Humid Conditioned Air and produces water at what point on the window casement does this happen ? Is it All the way In The Conditioned space or Does The Water Form outside the window seal outside of the conditioned space ?

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So explain to us how the water leak pointed out in your picture jumped back to the bottom of the sash without touching the bottom middle of the window frame. Typically the condensation will run down the window to the bottom of the sash. If the condensation is heavy enough the water flows to the corners of the sash where it weeps onto the window frames. The pooled water then leaches back up the sides. In this case since the growth is heavier on the sides there's most likely an air leak in that area also. Notice the darkest areas of the wood. That's where the water is pooling.

Air can easily move through an area that water can't.

Your concerns are logical Billy, unfortunately moisture intrusion and excess humidity/condensation are not, they can happen in strange ways and cause strange results.

I have seen the condition in the original photo many times in the MN cold climate and it has always been excessive moisture/humidity induced from the interior. Humidity condenses on cold window glass and in extreme cases, turns to frost; frost melts from sunshine and/or home heat turned up and water runs down glass to deteriorate protective wood finish. If left unattended, the wood finish gets destroyed and the the wood itself discolors and finally rots. Sometimes to the point of falling apart.

Note the "splintering" of the wood on the lower window frame. It's the finish turning fuzzy from alternate wet and dry cycles from frost melt. Also note that the entire lower frame finish is damaged, not just at the right side. Although the window weather seal appears to be leaking at the right side as well, it wouldn't have the affect of damaging the entire lower frame wood. The leak is allowing cold air to create even more frost at that location and so it's molding too.

Several common causes of excess humidity in the home have been noted by others already but I have also seen it caused by lots of people in a dwelling, either visiting (short term) or living there (long term). Both elevate the moisture in the air via breathing as well as cooking food, taking baths and so on. The worst I have seen was a home in a poorer part of town that had LOTS of people living in it (immigrants of some nationality or other) and so much humidity was being generated that several hours after they were gone and I did the inspection, water was literally running down the inside of the window panes in the house.

Even here in Nevada, as dry as it is, I recently inspected a home where the occupants had take a shower several hours prior to the inspection. The bathroom had no powered exhaust vent and so humidity induced, water droplets were still present running down the rooms window glass when I was there. The sill and frame was very moldy so this condition had been long term. Fortunately the window frame was vinyl or it would have been severely rotted. (See attached photo)

Originally Posted by Billy Stephens

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They Be Leaking.

contact a licensed competent window professional for repair / replacement.

Then time to move on.
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Originally Posted by Ken Rowe

So explain to us how the water leak

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That's his job.

contact a license competent window professional for repair / replacement.

* I could not ( with a DIAGRAM as a VISUAL AID ) successfully explain a contorted plumbing supply hanging six inches in the Air inside the 15 " toilet side clearance as NOT ALLOWED to you Ken.

Air can easily move through an area that water can't.

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The Width of a Window Sill ???.
* could you explain how this is Possible ?
** do you have a DIAGRAM ?
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Originally Posted by Bob Knauff

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Your concerns are logical Billy, unfortunately moisture intrusion and excess humidity/condensation are not, they can happen in strange ways and cause strange results.

I have seen the condition in the original photo many times in the MN cold climate and it has always been excessive moisture/humidity induced from the interior

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HI Bob,

As this Particular Example would be prevalent in a more severe climate ( aka Yankee Land ) I defer to your judgment.

Now if Ken can explain how Air can move through things common to construction of a home Water cannot-----
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Originally Posted by Billy Stephens

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HI Bob,

As this Particular Example would be prevalent in a more severe climate ( aka Yankee Land ) I defer to your judgment.

Now if Ken can explain how Air can move through things common to construction of a home Water cannot-----
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Not a problem. Roof vents, soffit vents, drip caps, kick-out flashing, dryer vents, furnace rain caps, I could go on and on.

Originally Posted by Ken Rowe

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Not a problem. Roof vents, soffit vents, drip caps, kick-out flashing, dryer vents, furnace rain caps, I could go on and on.

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Please Do.

Which one of those are Window Components ?
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Did anyone mention to see if the weather stripping is missing from the bottom or sides of the window?

It is an older casement window. They leak like a boat made from window screen!

The stains on the wood pretty much show the pattern of the water flow.

I would simply say that the windows are leaking and need repair but most likely replacement. I would also add that it is very possible that when the window is removed they will find damage to the wood framing in the area and they should not be surprised if they do find it.

Scott is exactly right. The window frame and surrounding components need to be replaced at this point. Next time you see a situation like that, just press a screw driver tip gently into the wood and see how soft it is! Also, most likely, there is more damage below, to the framing and such. Casements ARE the worst for loss of seal and operation and it only takes about 8 - 10 years to happen, it seems. High interior humidity will cause problems on any window glass, even fixed pane.

As an aside, it's often better to think in terms of "moisture" for issues like this instead of specifically water or humidity. Moisture can be either liquid or vapor. It sounds weird but this paradigm shift can make analysis easier at times.

The old wood frame windows in my house had similar effects as those in the posted photo. My house is a ranch and there is a 2' eave overhang so the windows rarely got wet from rain. In my house it was condensation that caused the problem.

Originally Posted by mathew stouffer

Any idea what might cause this. The majority of the first and second floor windows were in this condition. House was built in 1993.

Your past a mold stage with these windows.

You have a Fungus condition or (DRY-ROT) Time for new windows Bub.

Best

Ron