Moisture Barrier Around Windows

A window with a shade halfway drawn
  • 2-20 hours
  • Beginner
  • 50-500

When you are surveying the windows in your house, you may think about the glass, locks and the trim, but not a moisture barrier. This can be a mistake as making sure to include some kind of moisture barrier ensures that water, moisture, and vapor cannot find its way into your home ruining your decor, creating an unhealthy environment, and making your energy bills unnecessarily high. Here are a few options for moisture barriers and how to install them.


The easiest way to seal your windows and make a moisture barrier is to caulk. Caulk is relatively inexpensive and widely available. If you are unsure or nervous about taking windows out and applying materials inside your walls, start with caulk and see if it does the trick. If after applying caulk you still see moisture around your windows, then you know it's time to call in a professional. To apply caulk, simply squeeze out the caulk around window panes, placing extra caulk where you see any cracks or gaps that may be letting moisture in. Let the caulk dry and then survey to see if you need to apply another layer.


Tape can be used as a moisture barrier around doors and windows. There are specially formulated kinds of tapes made from aluminum or polyester that you simply apply directly to the window edges. To install correctly you must remove the windows and then place the tape all around the window, covering all the points that will come into contact with the wall. Though you do have to take the windows out to apply, this method is relatively low-cost and does not require a high level of technical knowledge.

Vapor Barriers

An increasingly popular option is to install a vapor barrier around windows which acts not only as a moisture barrier, but also keeps wind and cold out of your home, helping to heat it in a more efficient way. If you are building a home then you could insert the vapor barrier everywhere, over the foundations as well as in the walls. If you are interested in simply making your existing windows air and watertight, you can add a vapor barrier around the windows and/or on the warm side of already existing insulation. Vapor barriers are normally sheets of man-made materials and some are made of plastic, asphalt or a thinner film. If you are having trouble choosing your moisture barrier, speak to a professional at your local DIY shop about which kind of material might be right for your windows.

Once you have chosen your vapor barrier, remove the window and then apply the sheet of vapor barrier around the actual window. You can either nail it into place or use a special tape to attach. Use more than one sheet of vapor barrier, especially if you notice seams. During installation always make sure that the area you are working with is dry and free of dirt so that your moisture barrier materials can work properly and will not fall out of place.

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