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Wood Windows & Energy Efficiency: Infiltration

So, you have studied your wood windows, and have identified the different parts and respective terminology. (You have right? If not, read part one.)

Let's talk about air infiltration first. That's where Old Man Winter blows into the room, grabs you by the shoulders, shakes you and yells, "Cold enough for you?!" Don't you hate that? Yeah. Me too.

If your old wood windows have not been properly weatherized, cold air can be sneaky. When your old wood windows were installed, they were set into what is called a "rough opening". Big holes that the builders left in the wall to set those window jambs in. There is space below and above your window under the molding. That space was not originally insulated. And the boxes on either side of your window jamb? Where the weights go up and down? That wasn't insulated either.

Sometimes, the only thing between your bare feet and the icy cold outdoors is some window trim. One piece on the interior. One piece on the exterior. That's it. Don't believe me? Take a look. This is the bottom of the weight box for one of my dining room windows. I have taken off the piece of interior trim that covers it. That light you see? That is SUNLIGHT. From the GREAT OUTDOORS.

So, these uninsulated spaces on all sides of your windows can let it a surprising amount of outside air.

Another thing, even if you decide to replace your windows, that is not a guarantee that your contractor will insulate these spaces! So, new windows and smaller bank account, but same old heat loss. (I'll write about insulating these spaces later.)

You can experience heat loss in the following places if your window locks are not tightened and/or you have not weatherstripped the top, bottom and meeting rail. Window locks are not only for security. Tight locks force the sashes against each other and the window jamb so no air can get in.

Also, If your window sashes are too loose or too small, air can leak in at the sides of the sashes.

Finally, there are the pulleys. If you haven't insulated your weight box from the outside air, it can leak in through the pulleys.

But all of these spaces can be insulated against the cold. And, if you do it yourself, it isn't even that expensive to do it.

Next, we'll talk about thermal loss. Hopefully, I haven't scared you away just yet.

Posted by jeanne on August 1, 2007 at 9:34 PM (8)

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