Home>Discussions>INSULATION & HVAC>condensation ring on window
23 posts / 0 new
Last post
Blue RidgeParkway
Re: condensation ring on window

Normally the warmest part of a window unit in mid temperature ranges is the center point of the glass. I expect you are experiencing some temperature and humidity extremes.

A picture unit flanked by operable units you describe a large single area of glazing.

This article might help some in understanding the energy efficiency of windows.
You might also want to download the attached and blow it up so you can read it - a chart showing relative humidity indoors temperature outdoors on the various types of window construction/glazing layers.

Article: http://www.swissshade.com/energy_crisis.htm

Re: condensation ring on window

Thanks for the advice. there is nothing on the window as I have cleaned and scraped them. today with outside temp at 5 deg, the condensation ring actually turned to ice.

I am going to file a warranty claim with Pella and see if they will fix this. the window is really not very usable as this ring sticks around most of the day and also drips tons of water on the sill and often I get a 1/8 " puddle there.

I have 2 of these windows in the house and I get the same thing on the 2nd window although not as often and not as large. the 2nd window is under a covered porch and does'nt get exposed as much as the first.

Midwest Dog Mom
Re: condensation ring on window

Thought I'd throw my $.02 in, as I just had an Andersen rep at my home to assess the same problem.

I've had the same oval condensation problems on Andersen windows in my primary and vacation homes. The windows in both homes were installed in the early 1990's. I finally decided to call Andersen after I saw they warranty glass for 20 years, sure enough they sent out an Andersen authorized service person to check the problem.

The problem occurs when some of the argon gas that was between the panes of glass leaked out, causing a slight vacuum. The resulting "negative pressure" causes the two panes of glass to touch, which means the insulating properties of the window are compromised. Even though I only saw condensation on three or four windows, the rep said that Andersen wanted him to check ALL the windows in our house. He actually found a total of 13 windows that are defective.

Andersen offered two possibilities: repair of the problem, or replacement of the defective sashes. BTW, I have both casements and double hungs, and the problem is in both types of windows.

The repair consists of the tech taking off the closing hardware, and drilling a small hole in the frame of the window to let the pressures equalize. Then they seal the hold with silicone caulk and put the hardware back on.

The second alternative is to replace the entire sash; Andersen supplies the sash at no charge, but labor to install is not covered. In my area, the service company charges $35 per casement sash and $40 per double hung sash.

If you have the repair done, the warranty is still in effect and if the repair fails, you can still opt to have the sash replaced.

The tech told me that Andersen had been routinely replacing the sashes when the problems started (parts and labor covered), but now they offer the free repair and parts only for replacement. Apparently they were getting killed with the costs.

I'm still researching what the result will be if the repair is done. Will I still have an energy efficient window? There was some info on GardenWeb under "negative pressure window" that seems to indicate the repair is OK.

Hope this helps you in getting your issue taken care of. Good luck!

Re: condensation ring on window

I don't think if there were a seal failure allowing the Argon to leak would cause a " negative pressure" and allowing the glass to touch.
Since a gas used like Argon is more dense than air you would thing any breach in the seal that would allow that dense gas to escape would certainly allow less dense air to enter.
Also spacing between panes with gas filled windows can be between 5/8 to 3/4 inch it would be obvious if the 2 panes of glass were touching.

It could be an issue of some gas has escaped and there is moving currents within the gas space .... which reduces the insulating performance .... depending on the distance of the gap spacing between panes may be more affected toward the center.

Re: condensation ring on window

refering to another forum page isn't proof of anything.

Re: condensation ring on window

A couple of things that's .... ummmmm .... interesting from the above supplied reference source.


Most Insulated Glass Units (IGU) are filled with Argon or Krypton gas. They are both considered being "Inert Gases" and are used quite regularly in the industry. Argon is heavier than air and each molecule is larger, not smaller than an air molecule. When your glass was made it was more than likely built in a controlled environment that filled the IGU with Argon and sealed it shut. Ounce this is done and sealed the Argon level inside the glass is much higher than the air we breathe outside the glass.

Curious .... how does the mass of the Argon magically change ?


Well, it came about because the 100% argon between the glass panes in your windows decided that it would be better off with the 1% argon that is in the air that we breathe; and so, the little argon molecules packed up and moved out of the space. They have migrated out of the space, and since your windows have maintained their original air and moisture seal, nothing has gone in to that space to replace the lost argon – thus a vacuum has developed between your lites.

Since the Argon is able to escape then air would also be allowed to enter the space .... I don't think it's a one way street that would create a vacuum.

Re: condensation ring on window


Re: condensation ring on window

I have the same issue on two separate windows on a bank of 12 windows. I don't know where to look on the windows to find the manufacturer. There are some codes but no names.

Re: condensation ring on window

Try Rain-X. You will find it in the automotive department at your local department store or auto parts store in your area. I use it on my cars windshield. You can get it in a one use disposable wipe for about a buck.

Something else that is reputed to work is shaving cream. I haven't tried it but a lot of people use it on their bathroom mirrors to stop condensation.

As for the argon gas escaping, it can and probably does, but it does not leave a vacuum behind, exactly. In the summer, the gas, being in a confined space and heated up by the glass will expand and create a positive pressure. It can migrate through the glass and the seals, but only to the point that the pressure inside the glass envelope is the same as outside.

Then along comes winter and it gets cold. The gas in the envelope contracts and that is when the vacuum is formed. But as winter progresses, the gas inside the envelope should equalize by drawing air in. It is true that drawing air in is more difficult because air is mainly molecules like N2 and O2. Molecules are larger than the argon atoms. Argon is a noble gas and does not form molecules.


Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.