collasped windows and outside condensation

melmark4July 15, 2010


We have 18 yr old Anderson high performance windows. In March 2010 Anderson sent a tech out to repair the collapsed glass on all but 3 windows. The fix was the same that I have read online. My problem is that the last couple of weeks (July) we have had condensation on the outside on those windows that were fixed. Not everyday. Maybe 3x in 2 weeks. Today all windows were so bad you could not see out any of the windows. The condensation was so bad that it began running down the glass. I have been on the phone with the service rep then onto the sr. tech rep and up to an executive. I am told this is normal and the windows have not failed. This is the first time in 18 summers that this has happen. I understand(to a degree)about the relative humidity and dew point. Now I have read about what happens if 100% of Argon gas is used. Help! The executive from Anderson asked for three days to research the situation. Thanks in advance.


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What have you read about the use of argon and how it relates to your problem?

Condensation on the exterior of the outer pane of glass is normal. It primarily occurs in the morning but disappears as it warms up outside. Frankly, it shows your windows are working correctly.

    Bookmark   July 15, 2010 at 1:56PM
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It seems that I read that something about using 100% gas can cause the glass to collapse. Something to do with it being heavier than air and that barometic pressure difference can somehow collapse the gas. I find it hard to believe of never having a problem that this is normal. I could not see out of the windows. I will look to find what I read. It was back in 07 and was on this website. Thanks for your prompt reply

    Bookmark   July 15, 2010 at 4:40PM
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This is the reply from guy_exterior_man ( on Sat, Jan 13, 07 at 11:43

First, the collapsing phenomenon that you have experienced is actually related to a higher quality IGU (go figure) from the timeframe and technology level from when they were manufactured.

Even today, less than half of all dual pane IGUs have argon or any other gas fill between the lites. At the time your windows were manufactured the percentage was much smaller yet. Your windows, on the other hand, were made with 100% argon fill and the reason that I happen to know this is because if they werenÂt, then you would not have had the collapsed IGU that you are now experiencing.
(me again) I have read comments from Oberon and others that seem to support (at times) that the windows have failed or the seals have failed. Seems like there are also 2 sides if I lost the argon gas or not. I truly understand why a single pane would have condensation and even two panes if there is no inert gas or the gas is removed and just air placed in as a fix. Why have the inert gas in the first place if this problem will still occur? Thanks for your help to get me to understand just having a hard time accepting it.

    Bookmark   July 15, 2010 at 5:40PM
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Windows on Washington

If the condensation is on the outside surface of the outside piece of glass, this is a good thing.

The glass collapsing was a result of the law of partial pressures and the sealant used to create the seal between the two pieces of glass. The sealant used originally was semi-permeable to argon gas and would allow the gas leach through and reach the concentration that is was trying to get to. It would not allow the movement of atmospheric air back into the IGU to stabilize the now negative pressure environment inside the IGU. This is why the glass would become bowed inward.

The condensation on the outside is now a result of the more thermally resistant windows, courtesy of the full argon fill, performing as they should. If this condition diminishes over time, the windows have begun to loose their gas fill again.

    Bookmark   July 15, 2010 at 6:57PM
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Windows on Washington

The information contained herein is provided solely for informational and/or educational purposes. JELD-WEN disclaims any and all
liability associated with the use and/or provision of this information. Any reliance upon the information or advice is at the risk of the
party so relying. The information contained herein may be changed from time to time without noti cation.
© 2005 JELD-WEN, inc. and JELD-WEN, are registered trademarks of JELD-WEN, inc., Oregon USA.
he rst cold day of autumn hits. The windows fog up and water drips down the glass. A common reaction is
to pick up the phone and dial the window manufacturer. But dont worry! This is not an indication that your
windows are failing. The moisture on the glass is called condensation; a natural phenomenon that, in most cases, can
be easily eliminated.
Condensation occurs when excess humidity in the air releases on cool surfaces. The glass in windows and patio doors
usually provides a visible, cooler surface that shows the rst signs of condensation.
Windows in New, Energy-Ef cient Homes
Homes built today are more energy ef cient and substantially more air-tight than homes built just a few years ago. As
a result, air inside the home is better captured (saving energy), and there is less exchange with outside air (increasing
interior humidity).
Interior humidity builds up because the moisture from indoor activities has less opportunity to escape to the outside.
You may never have had interior condensation in your older home but are now experiencing it.
Family life style has a large impact on humidity levels. Activities such as cooking, long showers or baths, saunas, spas,
and laundry contribute to humidity levels. Variations in these and other moisture-generating activities often result in
one neighbor experiencing condensation and another not.
Replacement Windows in Older Homes
Condensation can also be seen in older homes where new windows have been installed to increase energy ef ciency.
The new, replacement windows are installed in an air-tight manner according to building codes. While this practice
keeps heat and air-conditioning from escaping, it also prevents moisture in the air from drying out. The older
windows had the opposite effect. They allowed heat and air conditioning to escape, but air exchange with the outside
air helped dry out moisture in the air.
High interior humidity can lead to structural damage to
your home (e.g. wood decay) and health hazards (e.g. mold
growth). Because these effects frequently occur unseen in the
wall cavity, the visible sign of condensation on glass is a good
clue that humidity levels are too high. Condensation on the
interior surface of glass is almost always due to high levels of
interior humidity.
Therefore, it is important to control interior humidity. Use a
hygrometer (an instrument that measures relative humidity in
the air) to monitor indoor humidity levels. This chart indicates
the humidity level at which interior condensation may occur for
different outside temperatures. As shown in the chart, when the
outside temperature gets colder, a lower interior humidity level
is needed to prevent condensation.
Outside Air
Temperature Inside Humidity at Which
Condensation Occurs
20° Over 35%
0° Over 25%
-20° Over 15%
The values in this chart are based on winter conditions of
70° indoor temperature with 15 mph outdoor winds and
double-glazed windows.
Condensation Page 2
JGI012 09/05
Consider installing dual-paned, insulating glass (IG). IG units tolerate more indoor humidity before "fogging
up" than single-pane glass units. For further protection, consider Low-E (a coating on glass that reduces radiant
heat-loss and the passage of ultraviolet rays).
■ Raise the average temperature of the house one or two degrees. Depending on many conditions, this can
greatly reduce condensation.
■ Open window blinds for air circulation. Closed blinds trap warm air in the space between the glass pane and
blinds. This air cools and releases moisture in the form of condensation. Blinds should be hung at least 4" away
from the window glass.
■ Use a ceiling fan to circulate warm room air toward windows.
■ Relocate heat vents to beneath windows and patio doors.
■ Do not block heat vents with furniture or other objects. The placement of these vents is intended to promote
proper air circulation throughout the house. This air circulation helps moisture in the air to dry out and also
distributes heat more ef ciently.
■ For unoccupied and unheated rooms, keep interior doors open. This promotes proper air circulation
throughout the house.
■ Vent all appliances to the outdoors. For example, if a dryer is vented into the attic or basement, all the moisture
from drying wet clothes is released into the house.
■ Run exhaust fans in kitchen and bathrooms.
■ Vent the attic and crawl spaces so moisture has a chance to dry out. Vent ducts should be clear of obstructions.
■ Make sure all vent ducts are clear of lint and other obstructions.
■ Turn humidi ers down as the temperature outside gets colder (if used for medical purposes, consult a doctor).
■ Be sure humidistat is located within the living space and not at the furnace outside of the heated part of the
■ Use a dehumidi er.
■ Dont dry rewood inside.
■ Have an air exchange system added to your heating system.
■ Building materials in new construction contribute many gallons of moisture to the interior air and it often takes
one year for all of the moisture to escape.
■ During the rst few weeks of heating during the cold season, condensation can be a problem due to the release
of moisture absorbed inside the house throughout the humid summer.
■ Quick temperature changes during the heating or cooling season can contribute to higher levels of
When the temperature of the exterior surface of the glass is cooled below the dew point of the outside air, moisture
forms on the exterior side of the glass. Then, as the glass temperature rises above the dew point, the moisture
evaporates back into the air.
Three main conditions promote exterior condensation:
■ High humidity in the exterior air
■ Very limited or no wind
■ Clear night sky
■ Close window coverings to reduce cooling of the glass by air-conditioning.
■ Remove or trim outside shrubbery near glass to promote air circulation.
As condensation occurs over time, moisture may penetrate wood. This could lead to wood decay. To help
prevent this from happening, keep windows and patio doors nished or painted and follow the suggestions in this
document to reduce humidity.
Condensation Page 3
JGI012 09/05
Vinyl windows and patio doors have a "weep" system designed to drain water to the exterior. If this weep system is
not draining properly, moisture may enter the surrounding wood structure and cause water damage. Clean dirt and
debris from weep holes with a thin piece of wire.
Aluminum is especially subject to condensation because of its high thermal conductivity (a measurement of the ability
of a substance to transfer heat). The temperature of aluminum will quickly change to the air temperature around it.
The colder the outside temperature, the colder the aluminum frame and the more likely condensation will occur.
Condensation is a natural phenomenon that occurs on exterior and interior glass surfaces. In nearly all cases, it is not
the result of a defective window or patio door. Care should be taken to reduce humidity with proper air circulation. If
condensation persists after following the precautions suggested in this document, contact a quali ed heating and air-
conditioning professional.
Condensation between glass panes is a different problem. If moisture is still present after cleaning the interior and
exterior sides of the glass, seal failure (when the seal between two panes of an insulating glass unit has broken)
between the glass panes could be the cause. If so, please call us for assistance.
For questions, feel free to contact us by phone or email.
■ Email:
■ Phone: 1-(800)-JELD-WEN / 1-(800)-535-3936

    Bookmark   July 15, 2010 at 6:59PM
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Thank you for all the replies. A little condensation I could understand but the whole window and all the windows? And why for the first time in over 18 years? And 4 months after the collapsed glass were fixed. Mind you I can not see out the windows. There is that much condensation.

    Bookmark   July 16, 2010 at 9:11AM
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Windows on Washington

If the condensation is on the outside, this is a good thing and not at all coincidental with your windows being fixed.

Close the blinds to the windows at night and see if that doesn't change the outcome slightly.

    Bookmark   July 16, 2010 at 11:03PM
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Hello everyone,
I'm back with a new question on the same problem. Had a window salesperson come out. Sat through the presentation. He used a BTU meter and a heat lamp on his window compared to ordinary glass and on a double pane and mine. Remember my collapsed class were fixed. The meter was set for 400. Ordinary glass read it read 400. Then double pane and the meter read like 320. His window read 40. My repaired window read 400. A brand new window I receivied from Anderson read 240. Anderson refuses to replace the widows stating their fix is all they will do and need to do. Should not my windows have the same btu reading as the new window? Still get condesation on the windows Having curtains or blinds don't seem to make a difference.
Thanks for your help.

    Bookmark   August 26, 2010 at 12:26PM
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You really helped us more than we could help you. If Anderson treats it's customers that badly no one should even think of purchasing one. There have been more than one tale of problems with Anderson windows here. There has been one thread posted by a contractor who said he loved Anderson and Pella because much of his replacement work comes from owners who had previously installed them.

    Bookmark   August 27, 2010 at 5:14PM
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