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plastic window sheets, and still condensation


hanky's Avatar
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Join Date: Oct 2002
Posts: 25

11-16-02, 10:30 PM   #1  
plastic window sheets, and still condensation

i installed plastic sheeting, the shrink stuff with the tape, and it's solidly sealed.
came home tonight, snowing outside, and there is again condensation on the inside of the storm window.
there are no leaks in the sheeting, and i applied it to the outside of the frame.
i did see some sill rot and could tell that the original condensation problem was because there wasn't a good seal in the window.
but now with the plastic covering it, i can't see why there's condensation on the inside of the storm.
my real question is whether the plastic is helping with the energy conservation inside.
???

 
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allan's Avatar
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11-17-02, 03:24 AM   #2  
Since terminology differs from area to area & country to country I will explain what I understand your situation to be . From the inside of the house out you have the plastic sheeting, an air space, a single pane window, another air space, then a single pane window which you are calling the storm. Is this correct? Is the plastic taped to the window casing or the wall? If it is fastened to the casing air is entering between the wall and the casing and then past the warmer interior window & condencing on the cooler exterior storm. If the plastic is attached to the wall I suspect air is migrating through the wall cavity via other means such as the electrical outlets on the exterior walll. Is the plastic helping conserve energy? Yes. A window is the weakest link in the wall as far as preventing heat transfer. Insulation is based on retarding air movement. Although the air space between plastic & window is too large to prevent convection air movement it does reduce heat transfer via conduction.

 
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11-17-02, 08:00 AM   #3  
thanks - now what about this?

thanks for your reply. and yes, you got the scenario correct.
the plastic sheeting is attached to the window casing.

so does this mean the area around the window is poorl insulated? and it's possible even if i replaced the Window, i'd still have this problem??
how do i make sure this doesn't happen when i install new windows?

 
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NJ

11-17-02, 11:41 AM   #4  
Flaw in window construction

The rough opening is larger than the window frame. The reason for this is the movement of the structure usually due to expansion and contraction. So there is a gap between the window frame and the framing of the wall, usually 2 to 4 inches depending on how old your home is. The same is done for doors. The molding or the casing covers this gap and in older homes on the sides of these windows this gap is used to house weights that act as counter balances to hold up the window when it is open.

It is difficult to identify your problem without seeing it. If you can bear with me, we will go through what is known as the process of elimination. Try applying the plastic to another window or windows in another room. If the condensation still occurs or is lessen as a result, then we can say the source of the problem exists on every window or does not, if it is less.

Even though your removed the rope caulking from the bottom of the storm window, make sure it is open. You should be able to see to the outside through the bottom of the storm window.

If none of this resolves your problem then look closely at the casing on the sides and top and the apron at the bottom of the window. You are looking for a gap between the casing or molding and the wall. If there is a gap there, the simplest solution is to caulk this gap with a paintable caulking.

Allan is correct in pointing out that the heated air is some how by-passing the window. Though in most cases plastic usually resolves this, in this case it did not. We will find the source of the problem if you will bear with me. You are also correct in assuming that new windows will not resolve this problem.

 
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11-17-02, 12:42 PM   #5  
i neglected to say i covered 3 windows upstairs with plastic ( from the inside of the house). all 3 have condensation today in the same place it was before - the inside-facing part of the storms.
i do not have any condensation on downstairs windows, or any of the 3 skylights that are upstairs.

i just don't know what to do now.i don't see any gaps between the molding surrounding the window, and the wall of the room.
is that where you wanted me to look?
in one of the windows, there was a crack along the bottom sill, but i covered the crack with the sheeting.

or, are you suggesting i try to caulk in the window frame between the single-pane and the storm? that air is leaking through there? say, behind the window tracking?
that's why the plastic covering the entire window frame didn't have an effect on condensation? because the warm air hitting the storm is coming from inside the wall and leaking through the frame?

the pattern of the condensation can give me a clue, correct? if it's huddled toward the right side of the storm, then the leak is likely coming from that area.

i took the plastic off of the largest window, and opened the storm a bit to remove the moisture.
now my question is where to look for the problem.
somewhere inside the room around the window? or between the window and the storm?

thanks so much for all your time and your knowledge.

 
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11-17-02, 02:14 PM   #6  
As resercon suggested, lets try eliminating sources. Remove the plastic from one of the windows and re install it taping it to the wall instead of the casing. As tight as it may appear air can get between casing & wall. See what happens. If condensation is present remove plastic and caulk around the frame of the interior window at its tracks. Wait 24 hours. Any condensation? If so now caulk where glass meets wood. Wait. Condensation? If there is, air is entering the space between the two windows from inside the wall cavity. Remove the casing, is there any insulation between stud opening & window frame? If not, apply a low expansion foam to insulate & seal this area. Your local building supply store can supply this & follow instructions on the can. Your upstairs windows are experiencing the problem because warm air rises. The warmer the air the more moisture it holds. The skylights are newer & are a two pane or thermal pane construction & better sealed. After all this you may want to replace your windows with more efficient thermal pane windows. Bonne Chance!

 
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11-17-02, 07:25 PM   #7  
resercon and allan -
thank you so much.
this is really a great service to have access to!
now that i understand all the factors, i can start the process of controlling variables and find the source of this problem! the science of oldhomeownership, eh?

thanks again for all your help.

 
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