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  1. #53
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    Aug 2003
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    Fort Worth, TX
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    11,358
    Quote Originally Posted by wptski View Post
    I can't say for sure if it went all the way around the perimeter of the frame but a foam was used from the outside before the trim and chalking was done.

    I've found the answer. Double pane LoE glass is better but it still isn't perfect when it comes to eliminating window condensation. The bottom of the fixed pane will be colder and if goes below the dew point, BINGO!
    Well, yes, that's true. What I was getting at is WHY it's going below the dew point. If it' strictly a flaw in the window unit, that's one matter. If it was not optimally installed and is experiencing a considerable amount of thermal bridging or bypass around the frame perimeter, that's another. I would not be satisfied NOT knowing which is the culprit. If you have an infrared thermometer, you can measure the window sill on a cold morning and see if it is approaching similar temps as the pane, or is considerably colder than the interior wall finish further into the room.

    I have installed double pane IG sliding glass doors in my own home, and over the summer did not note wide disparities in glass surface and frame temperature. I foamed the gap between the frame and the studs before installing exterior insulating foam sheathing and trim/siding. The key is not only to reduce heat transfer via conduction (insulation) but also via convection (air movement). The foam accomplishes both. Stuffing fiberglass batt insulation into the gap between window frame and stud faces is NOT the way to go, as fiberglass insulation does little to stop convective currents if the cavity it is installed in is not air tight.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  2. #54
    Join Date
    May 2006
    Location
    Warren, MI
    Posts
    941
    Quote Originally Posted by shophound View Post
    Well, yes, that's true. What I was getting at is WHY it's going below the dew point. If it' strictly a flaw in the window unit, that's one matter. If it was not optimally installed and is experiencing a considerable amount of thermal bridging or bypass around the frame perimeter, that's another. I would not be satisfied NOT knowing which is the culprit. If you have an infrared thermometer, you can measure the window sill on a cold morning and see if it is approaching similar temps as the pane, or is considerably colder than the interior wall finish further into the room.

    I have installed double pane IG sliding glass doors in my own home, and over the summer did not note wide disparities in glass surface and frame temperature. I foamed the gap between the frame and the studs before installing exterior insulating foam sheathing and trim/siding. The key is not only to reduce heat transfer via conduction (insulation) but also via convection (air movement). The foam accomplishes both. Stuffing fiberglass batt insulation into the gap between window frame and stud faces is NOT the way to go, as fiberglass insulation does little to stop convective currents if the cavity it is installed in is not air tight.
    The stuff they used was in a large pressurized can mounted upside down, like those paint sprayers. It was yellow colored. Infact, they had to come back because on one window it bubbled up through the caulking.

    I think that I mention above that the sliding pane doesn't get condensation on it! I couldn't figure out why the fixed pane was colder. I have a IR imager which shows that the one pane is colder at the bottom. One site I found said that as warm cools it falls. We all know that but it said that the colder air get trapped in the irregular shape of sash and causes that area to be colder.
    Bill

  3. #55
    Join Date
    Dec 2007
    Location
    Cedar Grove, Wi-Sheboygan
    Posts
    1,582
    The stuff they used was in a large pressurized can mounted upside down, like those paint sprayers

    If you happen to have a menards in your area they sell this set-up which is nice to have at this set-up allows the person to not waste a half a can of foam spray and can be used up to I believe 2 or 3 weeks later. They run about $50 for the set-up and the cans of foam cost a few pennies more than the regular foam cans.

    I'm going to be do that very same thing to all my windows by spray foaming the RO's as I know there's nothing in between them or very little if any insulation in them now.

    You have to be careful to use only the foam made for doors jambs & Windows so the foam doesn't push the frames inward causing you more problems then you care to have.

  4. #56
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,358
    Quote Originally Posted by wptski View Post
    The stuff they used was in a large pressurized can mounted upside down, like those paint sprayers. It was yellow colored. Infact, they had to come back because on one window it bubbled up through the caulking.

    I think that I mention above that the sliding pane doesn't get condensation on it! I couldn't figure out why the fixed pane was colder. I have a IR imager which shows that the one pane is colder at the bottom. One site I found said that as warm cools it falls. We all know that but it said that the colder air get trapped in the irregular shape of sash and causes that area to be colder.
    The operable pane having no condensation makes sense if you consider it is closer to the convective currents that occur next to a window when there's a wider delta T between indoors and out. The fixed pane is further out from the wall surface, hence it does not see as much air exchange. It in a sense is a dead air space formed by being further recessed from the room than the operable pane is.

    When many window treatments are closed at night to help retain heat inside the home, air between the window treatment and the glass will cool, as it is now isolated from direct contact with warmer room air. As it cools it sinks, pulling in warmer air from the top of the window treatment to replace it. Glass sections near this convective process will be closer to this flow of air, and more influenced by it, than glass sections further away.

    You can see if this is so by leaving the window treatments pulled away from the window in question (curtains open, blinds up, etc.) on a night you might expect the window to form condensation. See if all panes remain fog free overnight.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  5. #57
    Join Date
    May 2006
    Location
    Warren, MI
    Posts
    941
    Quote Originally Posted by shophound View Post
    The operable pane having no condensation makes sense if you consider it is closer to the convective currents that occur next to a window when there's a wider delta T between indoors and out. The fixed pane is further out from the wall surface, hence it does not see as much air exchange. It in a sense is a dead air space formed by being further recessed from the room than the operable pane is.

    When many window treatments are closed at night to help retain heat inside the home, air between the window treatment and the glass will cool, as it is now isolated from direct contact with warmer room air. As it cools it sinks, pulling in warmer air from the top of the window treatment to replace it. Glass sections near this convective process will be closer to this flow of air, and more influenced by it, than glass sections further away.

    You can see if this is so by leaving the window treatments pulled away from the window in question (curtains open, blinds up, etc.) on a night you might expect the window to form condensation. See if all panes remain fog free overnight.
    Convective currents is another way of saying the same thing mention in my other posts, cold air gets trapped in the jams. Correct?

    It doesn't matter if window treatments are opened/closed. All windows were replaced except one, a picture window which was replaced in 1990-1995. It's two solid seperate panes, nothing opens. I get the same condensation in the bottom corners as all the rest.
    Bill

  6. #58
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    Aug 2003
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    Fort Worth, TX
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    Quote Originally Posted by wptski View Post
    Convective currents is another way of saying the same thing mention in my other posts, cold air gets trapped in the jams. Correct?

    It doesn't matter if window treatments are opened/closed. All windows were replaced except one, a picture window which was replaced in 1990-1995. It's two solid seperate panes, nothing opens. I get the same condensation in the bottom corners as all the rest.
    The air in contact with the window surface is cooling and sinking to the bottom of the window opening. You could say it's "trapped"...a different term would be "stagnant".

    Refresh our memories about these windows...double pane, vinyl frame, low e glass? Some operable and some not?

    Without seeing the window construction itself I can't say much about the window's quality or the extent of effort taken by the manufacturer to thermally isolate the window pane from its frame. Some manufacturers are better at doing this than others. Bottom line I look for is that there should be some form of heat transfer resistant material (slow conducting) between the glass and frame, especially if the frame material is highly conductive, such as aluminum.

    Would you mind posting a few pics of these windows, concentrating shots on where the frame and glass intersect? What type of siding do you have on your house where these windows are? You may not be able to determine this easily, but I'd be wondering if the window nailing fins on the exterior side were properly flashed and sealed prior to the siding going up. Or were these replacement windows that went into brick veneer? These windows are harder to seal well, since the old window is often cut out (leaving the old nailing fin behind) and a new one installed with some creative fastening techniques where the old one stood.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  7. #59
    Join Date
    May 2006
    Location
    Warren, MI
    Posts
    941
    Quote Originally Posted by shophound View Post
    The air in contact with the window surface is cooling and sinking to the bottom of the window opening. You could say it's "trapped"...a different term would be "stagnant".

    Refresh our memories about these windows...double pane, vinyl frame, low e glass? Some operable and some not?

    Without seeing the window construction itself I can't say much about the window's quality or the extent of effort taken by the manufacturer to thermally isolate the window pane from its frame. Some manufacturers are better at doing this than others. Bottom line I look for is that there should be some form of heat transfer resistant material (slow conducting) between the glass and frame, especially if the frame material is highly conductive, such as aluminum.

    Would you mind posting a few pics of these windows, concentrating shots on where the frame and glass intersect? What type of siding do you have on your house where these windows are? You may not be able to determine this easily, but I'd be wondering if the window nailing fins on the exterior side were properly flashed and sealed prior to the siding going up. Or were these replacement windows that went into brick veneer? These windows are harder to seal well, since the old window is often cut out (leaving the old nailing fin behind) and a new one installed with some creative fastening techniques where the old one stood.
    All widows are vinyl and double pane LoE. All are new except the large picture window which I'm not sure is Argon, etc. gas filled like all the others. Two are double sliders and five are double sliders. All brick ranch home.

    All the new ones were built by that Chicago company(Republic) that locked out their employees just before Xmas last year, closed down and refusing to give severance pay! They were also sold at large commercial lumber yards for new home construction. It was widely covered in the news and mentioned by Obama one time.
    Bill

  8. #60
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    May 2006
    Location
    Warren, MI
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    941
    shophound:

    The picture shows a fixed pane on the left and a slider on the right. The stuff in the corner of the slider is clear sealant from when they were replaced, twice on that window because of marks inside the sealed pane!


    Bill

  9. #61
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    Was thinking about why heavier condensation occurs in bottom corners of IGU, leaving the tell tale "U shaped pattern". Well duh, it just hit me like a bolt from the blue. It's not just a matter of air being "trapped" in the corners, it is the corners themselves. An intersection of two thermally conductive materials combining as an enhanced heat sink vs. adjacent straight runs of framing that do not transfer heat at the same rate as the corners.

    Sometimes the obvious is not so obvious on the first pass.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  10. #62
    Join Date
    Sep 2005
    Location
    Texas
    Posts
    2,793
    Quote Originally Posted by shophound View Post
    Was thinking about why heavier condensation occurs in bottom corners of IGU, leaving the tell tale "U shaped pattern". Well duh, it just hit me like a bolt from the blue. It's not just a matter of air being "trapped" in the corners, it is the corners themselves. An intersection of two thermally conductive materials combining as an enhanced heat sink vs. adjacent straight runs of framing that do not transfer heat at the same rate as the corners.

    Sometimes the obvious is not so obvious on the first pass.

    wow...I'm going to have to chew on that for awhile

  11. #63
    Join Date
    May 2006
    Location
    Warren, MI
    Posts
    941
    Quote Originally Posted by shophound View Post
    Was thinking about why heavier condensation occurs in bottom corners of IGU, leaving the tell tale "U shaped pattern". Well duh, it just hit me like a bolt from the blue. It's not just a matter of air being "trapped" in the corners, it is the corners themselves. An intersection of two thermally conductive materials combining as an enhanced heat sink vs. adjacent straight runs of framing that do not transfer heat at the same rate as the corners.

    Sometimes the obvious is not so obvious on the first pass.
    No condensation forms at the top corners of the fixed window only the bottom and nothing on the slider either. The slider is exposed to the same outside elements as the fixed window. Trapped air isn't common to both on the inside. It happens to every window in the house.
    Bill

  12. #64
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    Aug 2003
    Location
    Fort Worth, TX
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    The whole "trapped air" terminology might be throwing this discussion for a needless loop, upon further consideration. Bottom line is that wherever there is condensation on your windows, that particular area of the window is below the dew point of the air surrounding that area, period. Stagnation of the air in those areas may be a contributing factor, a greater rate of heat transfer in those areas may be a contributing factor, deficiencies of adequate thermal breaks in those same areas may be yet another. Bottom line is that those sections of your windows get colder than surrounding components/surfaces, and they get cold enough to condense moisture from the air.

    If you are curious enough, find an energy rater/auditor who owns or has access to an infrared camera. Have your windows scanned during cold weather. You'll then see where the greatest amount of heat transfer is occurring with all of your windows.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  13. #65
    Join Date
    May 2006
    Location
    Warren, MI
    Posts
    941
    Quote Originally Posted by shophound View Post
    The whole "trapped air" terminology might be throwing this discussion for a needless loop, upon further consideration. Bottom line is that wherever there is condensation on your windows, that particular area of the window is below the dew point of the air surrounding that area, period. Stagnation of the air in those areas may be a contributing factor, a greater rate of heat transfer in those areas may be a contributing factor, deficiencies of adequate thermal breaks in those same areas may be yet another. Bottom line is that those sections of your windows get colder than surrounding components/surfaces, and they get cold enough to condense moisture from the air.

    If you are curious enough, find an energy rater/auditor who owns or has access to an infrared camera. Have your windows scanned during cold weather. You'll then see where the greatest amount of heat transfer is occurring with all of your windows.
    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.
    Bill

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