A little bit of insulation and caulk can make a big difference in comfort

Many homeowners incorrectly assume that if they have drafty windows, they need to have replacement windows installed. The truth is that replacement windows will improve your home’s comfort and energy efficiency, but they don’t always eliminate drafts.

[aside]Do I need replacement windows? Drafty window problems can often be solved without installing replacement windows (see the main story). But sometimes this expensive, whole-house upgrade is a worthwhile investment. If your house still has old-fashioned single-pane windows, replacement windows will make a big difference in comfort, energy efficiency and home resale value. You may also want to consider replacement windows if you have insulated (double-pane) windows with cloudiness or condensation between panes. Another important selling point for replacement windows is zero maintenance. Today’s solid vinyl, solid fiberglass and clad replacement windows never require painting like old-fashioned wood windows do.[/aside]

It’s all about the shim space

The real culprit in most drafty window problems is the shim space – the gap between the framed window opening and the frame of the window. When a house is built, the framing crew creates window and door openings that are anywhere from ¾ in. to 1 in. larger than the exterior dimensions of the window or door frame. This clearance ensures that the window and door units will fit easily into their framed openings. Carpenters then use wood shims as spacers when fitting the window and door units in place –hence the term “shim space.” Unfortunately, this air space is often left open, creating a pathway for frigid air to enter the house.
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You can’t see the shim space because it’s covered by molding (interior and exterior trim) that’s been nailed to the window jambs and to the wall framing. But you can feel the effects of an open shim space during cold weather, because frigid outside air will find its way around your exterior siding, into the shim space, and then around your window trim and into your living space. Brrrr…

Spray foam, caulk and an expert installer

It takes these three ingredients to effectively insulate and seal the shim space around your window and stop energy-wasting, uncomfortable drafty windows.

In some cases, an experienced energy technician will have to carefully pry off your interior trim to reveal the shim space. (The trim can be reinstalled later.) In other cases, the tech may be able to drill holes through the window jambs and inject spray foam into the shim space through these holes, using a special spray foam applicator (as shown in the video below).

Either way, the specially formulated spray foam will expand to fill the shim space, providing high R-value insulation as well as air sealing capability.

As a second line of defense against window drafts, the gap between your window trim and the gypsum wallboard can be sealed with a flexible caulk. This permanent drafty window fix can be performed on existing windows, or during the installation of replacement windows. It also works on drafty exterior doors.

As the temperatures dip, be sure to check your windows for drafts. Fixing them can save utility costs!