Weatherproof your windows

Simple steps to address condensation problem


Q: We have a two-story house built in 1939 with original double-hung windows in good shape and aluminum storm windows. In winter, the inside of the storm windows on the second-story (bedrooms) get some condensation on them. The house windows have metal weatherstripping (some missing).

Besides putting up foam tape around the house windows, do you have any suggestions without spending a lot of money to try to correct this? Also, is the condensation something to worry about? Could the condensation rot the window sill or something like that? I’d appreciate any advice. –Phil C.

A: There is a dead air space between the house windows and the storm windows, which is why having storm windows helps from an insulating standpoint. When air is allowed to move into that space, it carries moisture vapor with it, which then condenses on the cold glass and turns to liquid water.

To answer your second question first: Yes, the condensation is something to be concerned about. Repeated wetting of the wood can lead to mold, mildew, dry rot, and windows that simply do not work very well. Whenever you see the condensation appear, you should remove the storm window and dry out the wood rather than allowing it to remain damp.

There are two things that you need to address here: The first is the weatherstripping, because if you can eliminate the air movement, you’ll stop or greatly reduce the condensation. The metal weatherstripping you describe is difficult to repair, so you’ll want to find an alternative. I’m not a big fan of plain foam weatherstripping, because it’s too easily damaged.

I would suggest taking a picture of the windows, and then go and discuss this with a local glass shop. With the picture for reference, they should be able to help you select the appropriate type of retrofit weatherstripping to solve the problem. I would also recommend that you weatherstrip both the house windows and the storm windows, rather than just one of them.

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Because you’ve mentioned that only the upstairs windows are experiencing the condensation, the second issue to address is that there appears to be more moisture in the air in that area. This could be due to an adjacent bathroom without an exhaust fan; it could be poor circulation from your heating system; it could even have to do with the placement of the furniture and drapes in that room. I’d encourage you to do a little detective work and see if you can find reasons why the extra moisture is being created, and see if you can remedy that.

When your finances allow, I would strongly suggest that you look into replacement windows. The improvement in energy efficiency, operation and noise reduction with new insulated windows as opposed to older, single-glazed units with storms is considerable. The window dealer or your local utility company can even help you calculate what your utility savings will be, so you can see how long it will take to recoup your investment. The new windows will also definitely add resale value.

Q: I have a metal door that has a strip of vinyl material at the bottom. Can this be replaced? –Al S.

A: If you know the manufacturer of the door (you may be able to find it on a sticker on the edge or top of the door, or inside the frame) then you can check that company’s website on the Internet and see about getting replacement material. There may even be a local dealer who carries that brand of door, and will have a replacement door sweep.

An easier option, and what I ended up doing with my own metal exterior doors, was just installing an aftermarket sweep. Because exterior doors are a standard thickness, any home center or hardware store should have a replacement sweep that will work. They’re also easily adjustable up and down, so you can get a good seal against the threshold on the floor.

You’ll probably want to remove the hinge pins and take the door off its hinges, then set it on a couple of sawhorses. That will give you easy access to the bottom sweep, both for measuring and replacement.

Q: Is there (a weatherstripping) I can use on my nine patio doors? –Howard K.

A: Patio doors are actually treated more like windows, as they slide rather than swing. They usually have an integrated weatherstripping that looks like a strip of fuzzy fabric, which has a lot of compressible fibers that seal against the door frame when the patio door is closed. If that weatherstripping is worn and needs to be replaced, you should be able to get it through a window or glass company. They can also do the installation for you if you want.

Remodeling and repair questions? E-mail Paul at All product reviews are based on the author’s actual testing of free review samples provided by the manufacturers.

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