How efficient are single-pane windows?
Obviously, not very!
Notice the coolest temperatures on the left side of this window. That is the side where the sliding window is encased by the sash. That area is typically the most leaky.
In this case the temperature outdoors is about 45F.
And the temperature of the window pane and framing is just above that!
How efficient are single-pane windows? Not very!
A decent window pane, one that meets Energy Star standards for Virginia, would have a U-factor of .32 or less. That translates to an R-value of about 3. ** By contrast the walls nearby have insulation with an R-value of about 13 (if you include the brick on the outside).
The R-value of a single-pane window is about .5. That is virtually nothing.
That is not very efficient!
Remember, heat seeks cold. In the winter heat is getting out. In the summer heat is getting in.
My recommendation: older condos with single-pane windows should have replaced them years ago with something more efficient. Buying a condo with single-pane windows means the buyer is inheriting high energy costs year round for the life span of the purchase. Renting a condo with single-pane windows means the renter is inheriting high energy costs year round for the life span of the rental. Consider carefully!
** The best windows have U-factors of .12 or .15. If you are building a home, ask the builder what the U-factor is for the windows being installed. And you can look at the sticker. An instructive blog I wrote 2 years ago can be read by clicking here.
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560