Thanks. Where do I get the backer rod? Would using a piece of d-shaped
frost king rubber weatherstrip work?

Not sure if the windows are Anderson, but they are likely a similar window
to Anderson. By the way, one of the windows seems to have an mysterious
additional problem in which the thin wooden frame, on the inside of the
window, which holds the glass panel in place seems to get saturated with
water even when there is absolutely zero evidence of water dripping down
from the top. I suspect water is wicking through from the outside where the
frame holds the glass panel. Could this be solved just be putting some
clear silicone on the outside where the glass panel meets the frame that is
holding it?

Are you in the NJ by any chance?

Thanks,

J.


I am an Andersen Window Service Provider and this sounds like an
Andersen window! Very easy repair. What you need to acquire is 1/8"
or 3/16" rubber backer rod. Open the wndow up and get to the top of
the open sash. Cut a length of backer rod the width of the sash. Take
a stiff putty knife and press the backer rod under the flap to make it
spread more open. Close the window and the seal should be tight.
Sometimes you have to use different sizes of backer rod to get the flap
to touch the head jamb.

You can replace the sash w/s around the perimeter, but it sounds like
your problem is at the top of the sash.

That should do it!

jocobe