New sealed window units will fix fogging

Hey there, time traveller!
This article was published 17/03/2002 (8720 days ago), so information in it may no longer be current.

QUESTION — My problem is condensation between double pane windows. Some 10 years ago we had a sunroom added to the side of our living room. About a year ago, several of the windows developed cloudiness in the centre portion of the window.

I had thought that heating the windows with a hair dryer might help by displacing the moist air between the panes, causing the moist air to expand and leak out. If this is a proper solution, what would be the best time to do this? Would the winter be best or another time of year? Are there any other things to try?

There are nine windows and a patio door in this addition and I would say that the problem is mainly restricted to three windows on the south side. I am most interested to your solution to this problem.

–Joe Eisener, Dryden Ontario

Answer — There is one thing that is not perfectly clear about the “sunroom” addition mentioned above. Do the windows have “sealed units” or are they simply panes of glass encased in a frame that provides a minimal amount of thermal protection?

Many of this style of addition have poorly weatherstripped windows that simply provide weather protection, when closed over the screens. These units are normal designed for 3-season use and are not heated.

They provide a good means of ventilation and protection from uncomfortable mosquito and insect infestations. If this is the case, some fogging or frost between the panes of glass is normal and may be cleared by removing one pane and cleaning between.

Other “sunrooms” are properly insulated and heated additions with high quality windows and doors containing proper sealed units.

Unfortunately for Mr. Eisener, there may be only one solution to the fogging in his windows, if they contain proper sealed units. Replace the sealed units.

These higher quality windows may contain two or three panes of glass completely sealed from external air by one or two spacers, providing a higher thermal resistance than windows with individual panes of glass.

These units may have a partial vacuum between the panes, or be filled with an inert gas, such as Argon. Many of the newest windows also have a coating or film on the glass, providing even better protection from heat transfer.

The vacuum created between the panes of a sealed unit prevents air movement from inside to outside, thus reducing heat loss and condensation. The optional gas inside this space diffuses or changes the direction of the light and heat waves passing through the window, slowing the movement even more.

The protective coatings reflect some of this energy back from its originating side of the window, providing even less transfer to the other side. These last two properties may be equally important for cooling in the hot summer months, as they prevent warm sunlight from easily passing through to the cooler interior of the home.

It is a common problem with newer windows that have properly sealed units to lose their seal and develop “fogging” between the panes of glass. It may be worse on some days and almost invisible on others.

The causes of this may range from an original defect in manufacture or shipping damage, to low quality spacers, which deteriorate over time. Any small hole or gap developing in the spacers or sealant may cause a failure, and compromise the airspace.

If there is a small amount of fogging in a regular sealed unit, without Argon between the panes, it will not reduce the thermal properties of the windows to a large degree. It will, however, become an inconvenience on many days, preventing a clear view out of the room.

Heating the window with a hair dryer will do little to help clear the moisture between the panes of glass and will be a waste of time. Most windows of this type are designed to have the sealed units changed, with minimal effort and inconvenience.

Many sealed units are held in place with wooden or PVC stops and glazing tape or caulking. New units can be ordered from the manufacturer and often changed in less than an hour, with only minor touch-ups to the finish required.

This will be much less costly than upgrading the entire window. Many homeowners attempt these repairs themselves, to provide a renewed clear view outside the home.

Ari Marantz is owner/inspector of Trained Eye Home Inspection Ltd. and is the P. R. Rep. for the Canadian Association of Home Inspectors- Manitoba (www.cahi.mb.ca). Questions can be e-mailed or sent to: Ask The Inspector, P. O. Box 69021, #110-2025 Corydon Ave., Winnipeg, MB. R3P 2G9. Ari can be reached at (204) 291-5358.

trainedeye@iname.com