Just the other day someone asked me, “Robert, I know Seattle is wet and all, but why do I have puddles inside my windows?”
Unless you have experienced window failure and water is running in and behind the window, the likely cause is condensation on the inside of the window and frames. This is actually very common with older metal framed windows. With our humid Seattle air, it is very common on cold, humid days to see water condensing and pooling inside old or substandard windows.
What happens is that when it’s cold outside and there is warm, humid air inside the house, water will condense on the cold edges of the window. This is exactly the same thing that happens when you fill a glass with ice water on a hot summer day. The warm, humid air comes into contact with the cold glass and the water condenses forming water droplets that run to the bottom of your windows, forming those puddles that you are seeing.
In this case, although the water that is condensing runs down the window, it collects and eventually soaks into the window sill. This can lead to two main problems. The first is the deterioration of the window frames. Over time, repeated moisture can cause frames to rot and disintegrate. The other problem, which is extremely common in the Seattle area, is mold growth.
Mold around windows is commonly seen as patches of black dots around the most humid areas. While you may not think that this small amount of mold is bad for you, consider that this is simply the mold you can see that gives off spores at night, usually when we’re asleep in our bedrooms. Sounds nice right?
What can you do about condensation on your windows?
The first thing you can do is lower the relative humidity in your home. I know it can be hard to do during our humid Seattle winters, but there are a few places to start. Check that bathrooms are properly ventilated. Showers generate a large amount of moisture and this can spread throughout the house.
Inspect your dryer vent and confirm that it is properly connected and working. You may also consider using a dehumidifier to reduce the total amount of moisture in the air.
The most direct way to solve the problem is to stop the condensation at the source; the place where the water condenses. Replacing your low-efficiency windows with high-quality windows will usually solve the problem. Older windows let in more cold from the outside and magnify the moisture problem. Newer vinyl windows with insulated frames reduce or eliminate condensation problems. Also look for windows with some kind of ‘warm edge technology’.
Traditional windows have metal spacers that separate the glass panes. This metal acts as a short circuit that transfers cold through the glass to the inside, causing condensation around the edge of the window frame.
Whatever you do, I strongly recommend that you take some measure to prevent condensation from repeatedly forming on window frames. Even if you live in Seattle, you shouldn’t have puddles inside your windows.