Do It Yourself Energy Efficiency Projects: Your Home’s Thermal Envelope (Part 3): Windows

By Vernon Trollinger, January 22, 2010, Energy Efficiency, Home Improvement

There are a few things you can do around your home to save money during the remaining winter months and the hot summer.  Basically, you need to air seal your home's "thermal envelope"; the sum total of the home's insulation systems including walls, ceilings, foundation, floors, windows, and doors.  These work more effectively with good, tight fits that seal-out the weather, moisture, and air.

By having a tight seal, the less energy you waste or lose by exchanging it too often with the air outside.  

You might believe that work I describe below is beyond your ability.  Never fear, these are easy tasks for any average person.  Make sure you have a good set of tools.  Plus, you might want to look at the Federal Energy Efficiency Tax Creditand save on your taxes, too.

One word of warning: you will get a little dusty and dirty.  

And now: Windows.

If you have double-hung wooden sash windows with storm windows that are drafty, there are several ways to make them more energy efficient.  Make sure the glazing on the glass panes of the sash windows is not cracked or crumbling.  The glazing helps hold and seal the glass to the wooden window and thus blocks drafts and quiets rattling — especially from traffic.  It also lessens the likelihood that the glass will break if a pet or a child presses against it.  Glazing is something of a skilled art.  That being said, it's not that hard to do.  Re-glazing a window yourself can save you $50 to $100 or more.  All you need is glazing putty ($5), a putty knife ($2), some glaziers' points ($2 for a box of 100) and some time.  

First, remove any old, cracked, or crumbling glazing with a putty knife.  Glazing putty takes a long time to cure but it will be very, very hard and will last decades.  It can be loosened with a heat gun, but keep the gun moving or the heat will crack the glass.

When the old putty has been removed, pull the old glaziers' points with a pair of needle-nose pliers.  Now, lift out the pane and set it aside.  Sand the channel where the pane fits on the wooden sash.  Usually, I apply a thin bead of silicone caulk in this channel before replacing the glass.  This helps to seat and seal the glass pane.  This especially helps when working on multiple small panes (called "lights") separated by thin or fragile wooden mullions (also called "muntins").  Next, insert new glaziers points.  This is done by using the putty knife to press points into the wooden sash along the glass pane to keep it in place.  Take your time so that you don't break the glass.  

Glazing putty can be purchased in either a can or a tube with a shaped tip that fits in a caulking gun.  However, it does take some practice to get just the right angle and right amount of putty on the glass.  When using the tube mix, keep the 45 degree angled tip steadily against the glass and lay a bead of putty the length of bottom of the pane.  If you're using the putty from the can, roll the putty into long snake (or rope) and place it along the edge of the pane and along the wood.  Gently press it into position so that it forms a nice 45 degree angle with the putty knife.  The putty is shaped this way so that water runs off the glass to the edge of the window sash instead of into the window pane channel where it can rot the wood.  

The next thing to look for is if your windows close snugly.  Both the top and bottom window have what is called a "meeting rail".  On the upper window, it is the bottom of the window and on the bottom window it is the top.  These meeting rails are shaped so that they mesh together when they close.  This helps seat and seal the window properly.  Check to see if the bottom window runs firmly –but not too tightly– along the window jamb as you close the window.  If it's too loose and wiggles back and forth, it probably won't seat very snugly when it's closed.  You can use a putty knife to pry out the window jambs and then re-position them to fix this.  You might try adding felt or self-adhesive foam weather stripping.  Also, make sure you clean out any debris from the window to ensure the window will seat and seal snugly.  

As metal storm windows age, the harder they seem to close.  This usually happens because of dirt and corrosion.  Make sure the window tracks are clean and free of dirt and debris so the window runs smoothly.  

Outside, check that the storm window frame is held tightly in place against the wooden window frame.  Screws that hold this frame in place might be loose and might need to be replaced or moved to a new spot.  Most drafts from storms windows come from where the storm window frame meets the wooden window frame.  Once you're certain the storm window frame is secure, lay a bead of caulk into the seam where the metal storm window frame meets the wooden window frame.  Typically, there are two slots cut into the bottom apron of the storm window frame.  Do not seal these.  These are weep holes that allow condensation to escape.  

If you have modern, double glazed windows (windows with inner and outer panes of glass), one of the things to look out for is fogging between the panes.  Double glazed windows are made by attaching a pane of glass with adhesive to either side of a half-inch wide aluminum frame either in a vacuum or a hot, dry environment.  It is then a single glass unit and is installed into a standardized window frame with adhesive.  Fogging is a sign that the seal on the glass unit has failed and water vapor has penetrated into the space between the panes.  If the fogging is still present in summer, it's a good guess that acids have also leeched in with the water vapor and have permanently etched the window glass.

If the fogging disappears when the window warms, then it's not too late to treat it.  Examine the wood of the window for any discoloration from moisture.  Look for peeling, flaking paint or soft, gray-colored wood.  If you find some, sand it smooth and then seal it with an oil-based enamel or polyurethane.  If the wood is very soft, you might try using an epoxy formulated to penetrate and preserve rotten wood.  Be sure to mask the glass first with painter's tape.

Visit the Bounce Energy Education Center for more tips on saving energy. 

Stay tuned for next time:  Wind, Weather, and Storm: Door and Window Tips (cont.)
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