money out the window

Heat Loss Through Windows. Once Again

With the white stuff just around the corner. (I know it’s coming, I can see it up on the hills), I am getting more calls than last month about insulated window coverings. Or, in layman’s terms, how to keep the cold out and the heat in.

I’ve written about this before, but it bears repeating. Do you understand that 25% of your heating bill is going directly out your windows?  That’s a number produced by Hunter Douglas, and one which I’ve seen backed up by several studies from the U.S. Government among others.

If you think your super-dooper new windows are protecting you against this loss, sorry, they aren’t.

HOW MUCH?? Yes, 25% of your heating bill is wasted.

This means that out of every $100.00 you spend on your heating bill, $25.00 is going directly out the window. It’s the same as if the window was open and you threw $25.00 through it. Every month you use heat. If you have air conditioning, this 25% applies to those months as well.

How do you fix this?

You can replace the windows, but that will only decrease the loss. A bit.

You can put insulation over the windows. This can be plastic on the inside, or outside. But, this won’t help much either.

You can put insulated window coverings over the windows. These will also not STOP the loss, but can reduce the loss so substantially that the payback can be measured. You can tell how long it will take to break even on the window covering cost.

insulated roman and drape

You can reduce the heat loss through your window with insulated window coverings. For example, some cellular shades can provide an added R-value to the window of up to 7. An insulated, blackout-lined drapery with valance and Roman Shade can increase the R by about 17

That’s a substantial change in heat loss.


A few things to know about heat loss through windows:

The insulation in your walls is rated at a R-24. (If it  is to code.)  The R stands for resistance to heat flow. Some highly insulated homes, like straw-bale, can have an R-value of 40 or more.

Heat loss through windows is actually measured as a U-value. It is rare to find windows with a listed U-value, the public gets R-ratings for windows too.  The best windows readily available to the public have an R rating of between 4 and 5. There are windows with an R-value of 7 to 11, but they are not yet commercially available.

For info on how to find out how much YOU are sending out your window, and what difference your window coverings is making to that heat loss, email me at 

Read more about heat loss:
Layers are the Key

My Heat-loss Rant for the year

Photo credits and attriburtions

Copyright: <a href=’’>blamb / 123RF Stock Photo</a>

winter scene
Copyright: <a href=’’>yegorov / 123RF Stock Photo</a>

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