Condensation on windows

[Shophound]

I "think" that I mentioned above somewhere that I own a IR imager which shows those areas to be colder than the rest of the window sash. That holds true wether the window has a single or double slider. The open area where the window slides or where the fixed window is was always colder.

Re: IR imager: It's a long thread and I slept since it started.

Do you have an image from the scanner you can post here? It would be interesting to see.

[wptski]

Back on 1/16/09 on a night that went down to 5F. Markers are in F, of course!

[Shophound]

Back on 1/16/09 on a night that went down to 5F. Markers are in F, of course!

Excellent shot! Now, for clarity purposes, am I correct to assume the pane on the right is the operable pane, while the one on the left is not? I would further assume that if this is true, this image was taken from inside the home, given the temperature marker readings.

With that in mind, and with the above assumptions being true, just going by what I see above, it appears the colder regions are thermally bridged to the exterior nailing fin of the window and external structural components of the building, explaining the colder surfaces, whereas the operable pane and interior frame, being warmer, are thermally bridged to interior components of the window frame and internal structural components. It is also possible there is air movement in the two lower opposing corners between the frame that holds the fixed pane in place, and the structural members that hold the entire window frame in place. The dark purple to black areas indicate the coldest regions, indicating very low resistance to heat flow is occurring in these areas (can also be stated as a very rapid rate of heat transfer from dwelling interior to exterior, leaving the surfaces cold).

Is this window set in a brick veneer wall, or is it some other form of siding? If the latter, is it possible to remove exterior trim underneath the exterior side of the window assembly and investigate for any insulation or lack thereof? Is the bottom portion of the window assembly provided with drainage/weep holes?

[wptski]

Yes, the fixed window is on the left and taken from the inside. There isn't a nailing fin or lip on these windows, they slip inside the framing up to the stop strips. They are screwed into the window framing from the inside of the sash. It's a brick home and expanding high R value foam was used from the outside brfore the trim pieces were added.

Here's another window on the same night except this one has two sliders, you can see the right side edge of the right hand slider. The center fixed window area is colder than both sliders. Room size and imager lense won't allow a shot of the whole window.

[printer2]

I have the same style of window in my sunroom, low E argon filled. Same pattern of condensation, or in my case ice at times. As shophound said it is conduction loss from two thermally conductive areas due to thermal bridging. The non-moving window also has stagnation happening due to the recessed position relative to the inside air.

The same effect happens to the warmer, sliding window but in reverse. It is recessed compared to the outside air and heat loss off this window is less because of less air movement up the pane. Do you have window screens on the outside of this window? It would also cut down on air movement against the surface of the window.

I have watch my windows fog up in real time at an accelerated pace while soaking in my hot tub while it was -15C out. At -30 or -40 it is more trouble than it is worth using the tub due to the condensation forming and the windows freezing shut (I keep the room a bit above freezing in the winter).

My windows have weeping holes on the outside for any condensation that forms on them to drain outside. I would guess yours have the same. Other than appearance I doubt the condensation would do much harm.

My guess would be that your windows are doing all that they can.

[wptski]

I have the same style of window in my sunroom, low E argon filled. Same pattern of condensation, or in my case ice at times. As shophound said it is conduction loss from two thermally conductive areas due to thermal bridging. The non-moving window also has stagnation happening due to the recessed position relative to the inside air.

The same effect happens to the warmer, sliding window but in reverse. It is recessed compared to the outside air and heat loss off this window is less because of less air movement up the pane. Do you have window screens on the outside of this window? It would also cut down on air movement against the surface of the window.

I have watch my windows fog up in real time at an accelerated pace while soaking in my hot tub while it was -15C out. At -30 or -40 it is more trouble than it is worth using the tub due to the condensation forming and the windows freezing shut (I keep the room a bit above freezing in the winter).

My windows have weeping holes on the outside for any condensation that forms on them to drain outside. I would guess yours have the same. Other than appearance I doubt the condensation would do much harm.

My guess would be that your windows are doing all that they can.

Yeah there are screens for the sliding part of the window. I have the weeping holes also.

Right, no real harm but I didn't expect to see any condensation on my new windows. As many people that I've talked to, even glass manufacturer's never stated that it's normal for a doulble-pane Argon filled window! Only a triple-pane will cure this. I've searched on the topic but never used the right search string. Once I did, I found the answer at a page at UC at Berkley where tests where done. That's the best those windows can do!

[Shophound]

I have the same style of window in my sunroom, low E argon filled. Same pattern of condensation, or in my case ice at times. As shophound said it is conduction loss from two thermally conductive areas due to thermal bridging. The non-moving window also has stagnation happening due to the recessed position relative to the inside air.

The same effect happens to the warmer, sliding window but in reverse. It is recessed compared to the outside air and heat loss off this window is less because of less air movement up the pane. Do you have window screens on the outside of this window? It would also cut down on air movement against the surface of the window.

I have watch my windows fog up in real time at an accelerated pace while soaking in my hot tub while it was -15C out. At -30 or -40 it is more trouble than it is worth using the tub due to the condensation forming and the windows freezing shut (I keep the room a bit above freezing in the winter).

My windows have weeping holes on the outside for any condensation that forms on them to drain outside. I would guess yours have the same. Other than appearance I doubt the condensation would do much harm.

My guess would be that your windows are doing all that they can.

You nailed it, sir.

For the OP, to avoid any condensation on your windows (when it is 5°F outside), at your 65 degree indoor temperature set point you would need to keep your indoor relative humidity level below 35%. This is based on your coldest reading from your IR scans indicicating 37 degrees. If your home has a humidifier, consider lowering the setting before going to bed, and raising it during the day when outdoor temperatures rise. Also consider source control; run exhaust fans when cooking and showering if you're seeing indoor humidity levels increase sharply during daily activities.

A 57 degree center-of-pane temperature isn't bad if it's 5 degrees F on the outside of that glass. I would expect the edges to be colder for any double pane IGU of decent quality. How much colder seems to be the main issue of concern here.

[wptski]

You nailed it, sir.

For the OP, to avoid any condensation on your windows (when it is 5°F outside), at your 65 degree indoor temperature set point you would need to keep your indoor relative humidity level below 35%. This is based on your coldest reading from your IR scans indicicating 37 degrees. If your home has a humidifier, consider lowering the setting before going to bed, and raising it during the day when outdoor temperatures rise. Also consider source control; run exhaust fans when cooking and showering if you're seeing indoor humidity levels increase sharply during daily activities.

A 57 degree center-of-pane temperature isn't bad if it's 5 degrees F on the outside of that glass. I would expect the edges to be colder for any double pane IGU of decent quality. How much colder seems to be the main issue of concern here.

My RH was set to 30-33% during the winter. I kept dropping it from around 40%. I'm not going any lower than 30-33% as that's dry enough as it is and may even increase it!

[Shophound]

My RH was set to 30-33% during the winter. I kept dropping it from around 40%. I'm not going any lower than 30-33% as that's dry enough as it is and may even increase it!

Well, that's the solution with your present windows if you want a completely condensate free winter. Otherwise you will see condensation on really cold days. I have lived in homes for years where condensation was a regular winter occurance, and since the windows had non-wood frames I don't recall any adverse effects from the bouts of condensation other than fouling the glass after a cleaning. Where I have seen it be a problem is where it runs onto a window sill and is allowed to stand for a long time without being wiped up...the paint chips up and/or it gets moldy there. But that was with single pane aluminum frame windows, where the frames sweat worse than the glass.

[wptski]

Well, that's the solution with your present windows if you want a completely condensate free winter. Otherwise you will see condensation on really cold days. I have lived in homes for years where condensation was a regular winter occurance, and since the windows had non-wood frames I don't recall any adverse effects from the bouts of condensation other than fouling the glass after a cleaning. Where I have seen it be a problem is where it runs onto a window sill and is allowed to stand for a long time without being wiped up...the paint chips up and/or it gets moldy there. But that was with single pane aluminum frame windows, where the frames sweat worse than the glass.

A RH of 30-33% doesn't mean condesation free! Probably have to go to 25% or lower for that.

Funny, my neighbor has the same windows, claims his RH is 45% and no condensation. I tried to get a comment from him after actually see a fogged bedroom window in his house one night. I didn't bother to challenge his statement.