Condensation on Lower Corners

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Scott W
Posts: 1
Joined: Tue Dec 26, 2017 8:28 pm

Condensation on Lower Corners

#1 Post by Scott W »

Does anyone have an explanation for this issue? A little background, The windows are "Replacement by Anderson" Fiberglass. This is happening on (3) different windows, (1) west facing and (2) north facing. The condensation is along the bottom of the glass about 1/2" band. The unusual part is along the sides of the fiberglass about 2" up from the sill, there is a spot on right and left, about 1" diameter where there is a concentration of condensation. The rest of the frame is dry and cold, no condensation anywhere. The outside temp is between 0 degrees and 10 above Fahrenheit. The inside humidity is between 50 to 60%. I can provide pictures if it will help. We are concerned there is an issue with the windows construction. Any insight about this would help. Thanks.

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Windows on Washington
Posts: 5310
Joined: Fri Oct 27, 2006 11:23 am
Location: DC Metropolitan Area-Maryland/Virginia/DC

Re: Condensation on Lower Corners

#2 Post by Windows on Washington »

From the outset, your Relative Humidity levels are way too high inside the home right now with the exterior temps that you are quoting.

With those type of temps, you shouldn't be North of 35% to be honest.

Now...to the other part of your questions, it is due to the thermal conduction at the corners. The most insulated part of the window is the center point of the glass (furthest away from the edges and the spacer).

The corners will suffer from both the conduction issues as well as normal air leakage at the corners. If the windows are gushing air, you will see more condensation issues with regards to interface locations in the weatherstripping profiles.

Step 1 is to reduce your indoor humidity to a reasonable level. Max 40%.

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HomeSealed
Posts: 2996
Joined: Mon Feb 15, 2010 3:46 pm
Location: Milwaukee, Madison, SE Wisconsin

Re: Condensation on Lower Corners

#3 Post by HomeSealed »

+1. Your RH is far too high to avoid condensation. Here's a neat tool to play around with regarding temperature and RH: http://dpcalc.org/
35% as WoW mentioned will be a nice target, but with subzero exterior temps and double pane glass, you may very well still see some condensation even at that range. There are other factors as well, including the circulation of interior air (to warm the glass up thereby reducing condensation) which can be impeded by window treatments, furniture, etc....

Ultimately, the bottom line is that what you are experiencing is not a sign of any issue with the window. Further, when the temps get that low, you may have to trade off comfort (very dry air) if you want to completely eliminate the condensation.

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