The Three Problem Areas of Windows

 Boarded Window

Windows can be a major source of drafts, and in some cases, an avoidable source. As windows age, as your house settles, and as materials warp and wear, gaps and cracks in sealants used to prevent air infiltration can occur.

The good news is that these problem areas are often easily fixed.


In general, there are three areas to check around a window. Some people like to wait for a cool and windy day and hold a lit candle or wet hand up around the window perimeter and check for any drafts. While that method is the most thorough, anytime is good for a plain old visual check, which can reveal some problems as well.

The three areas to check are:

1. The "seams" where the window frame attaches to your interior wall.
2. The outside window frame "seams"
3. The seal that forms when the window is shut.

When checking the interior and exterior seams, look for gaps and cracks in the caulk that was originally used to seal the window.  Caulk does degrade with age, and over time the sun, heating, freezing, etc will result in separation from the surface, gaps and/or cracks.

Removing Old Caulk

If the caulk is starting to degrade you will want to remove as much of the old "bad" caulk as you can and replace it with a fresh application of an acrylic latex caulk or a polyurethane sealant.

To remove the old caulk, you will need a putty knife and you may wish to try various caulk removers that are available at hardware stores. The removers need some time to work, but can make removal of old caulk easier.  Once removed, clean the surface and apply your new caulk.

Choosing New Caulk - What To Buy

When buying caulk, note that some types are made for interior use, some for exterior, some are paintable, some are clear, some are white, and some are rated to last longer than others.  While we're at it, some caulks are even rated to withstand extremely high temperatures, which you may need when sealing furnace flue penetrations or light fixtures, but I digress.

Anyway, acrylic latex caulk is usually a good choice for sealing windows, and many varieties are paintable and suitable for indoor or outdoor use.

Applying Caulk

Occasionally, you can find caulk that comes in flexible tubes that allow you to simply squeeze the caulk out to apply. Usually these tubes are relatively small, but the convenience of squeezing is nice.

Most often, caulk comes in standard cylindrical tubes with rigid sides. these tubes are made to fit a caulking gun. Caulking guns are simple devices meant to apply constant pressure to the tube, resulting in quick and easy installation (with a bit of practice).

Usually you can purchase a good quality caulk gun for $10 to $15. I've found it is best not to skimp on the cheap $5 ones - those ones won't apply even pressure, will make your hands tired, and will crack, bend, or wear out.

The keys to applying caulk are:

1. Start with a clean, dry surface.
2. Apply caulk in an even, consistent bead.  It may take some practice, but you'll get it.  
3. Avoid applying too much caulk.  Most beginners apply two or three times more caulk than needed, making for a messy cleanup.
4. Smooth out the bead and press the caulk into place with a wet finger.  You can try a plastic caulk applicator if you want, but those aren't necessary.
5. Have a damp rag and some paper towels nearby for cleanup.

I mentioned above that beginners often apply to much caulk.  Along those lines, beginners using caulk guns often move too slowly.  When the caulk gun is depressed and caulk begins to come out, you generally want to move quickly and smoothly along the surface.  This helps prevent too much from accumulating, and results in a consistent application. Of course, if you have a large gap you'll want to move slowly to allow the gap to be filled.

Finishing

After applying you will want to smooth out the caulk with a wet finger or applicator, as mentioned above. While it is freshly applied you should be able to clean any messes or mistakes relatively easily with a damp rag or paper towel.

Most caulk requires several hours to set. Follow the directions on the caulk and wait for it to set before painting.

What About the Seal of the Window?

We've talked all about caulking the seams of the window, but what about the seal formed where the sill and the sash meet when the window is closed?

In many cases, windows do not form a tight seal when closed. This is a job for weather stripping - the type of weather stripping to use varies by window type and your own preference.

With double-hung and single-hung windows, self-adhesive foam weather stripping works fine on the edges of the windows that sit in the sash. With casement windows, you can apply self-adhesive weather stripping on all four sides. If you aren't sure what type of window you have, see this wikipedia article outlining window types.

In all cases, make sure you are applying the weather stripping to a clean, dry surface.

Lastly, with single and double hung windows, you may benefit from installing v-channel weatherstripping along the moving parts of the window. This video from easy2diy.com shows how to apply v-channel.

Types of Weatherstripping

If you are unfamiliar with weatherstripping types, it may be worth a quick trip to the hardware store to check out your options. In general, there are varying thickness and widths available. For windows, you may find self-adhesive or non-adhesive weatherstripping (the latter requiring nails or staples to apply).

Closed-cell foam and rubber are the most common materials.

For windows, you generally do not need much width, and the key is to buy a weather stripping just thick enough to seal the gap, but not too thick to impede closing the window all the way.