custom casement weatherstripping for draft problem

A home owner from Chicago area says:
I have custom double casement window sashes (made at a mill...please see 5 photos). Where the two sashes meet (when closed), there is vertical bulb weatherstrip in a kerf (slit in wood) for keeping the air out. Unfortunately, at the top and bottom (where the two casements meet), there is a small draft. In fact, for some of the windows on a sunny day, if you look at the correct angle, you can see a tiny pin sized hole of sunlight. When I mentioned this to the contractor, he put adhesive felt like material on the left and right the top and bottom...on the sides of the casement windows. When the casement windows were closed, the two pieces of felt like material were in contact with each other and filled the gap. Problem solved...except for the felt like material either had bad adhesive properties or it was structurally destined to fail given that the felt like material continually rubbed against each other as one opened and closed the windows (it was on a friction part of the window). The felt like material eventually started peeling off in a few weeks due to the continuous rubbing that occurred when opening/closing. As a temporary solution, I would just shove white cotton batting at the top and bottom where the casement windows met when they were closed (you can see the cotton batting in the attached pictures). It functionally served the same purpose as the felt like adhesive. However, I could no longer use our windows without always having to redo the cotton batting...very annoying. A few questions:

1) Should I try to find a more permanent version of the felt like material (staple or nail it in the side of the window), or is it bad to have weatherstripping at a friction point...since it will eventually fail? Any ideas? If possible, I would like to avoid nailing something into my new windows unless it's going to work for the long run.

2) Is the problem possibly with the vertical white bulb weatherstripping in the kerf? Perhaps, it needs to be a different shape/thickness? Perhaps, it needs to be slightly longer than the window at the top and bottom so it provides an additional filler at the top/bottom when the casement windows are closed, but maybe this would just eventually rip. Does this make sense? Will it work in the long run?

3) I can't go back to the original contractor (who was hard to find in the first place). What type of person would I hire to diagnose/solve this problem? Who would be a weatherstripping expert for truly custom windows? Carpenter? All of the window guys are typically "new window" specialists/installer (Marvin, Pella, etc).

I'm trying to figure out weatherstripping solutions that would solve this problem (or figure out who to hire and how to find them). I am open to any ideas. I appreciate all of your help.

User submitted photos of their custom casement window.
Profile picture of Paul
Paul from SWISCO responded:
Well, you may be able to use the Swisco 58-026 Stick-on Weatherstripping, but I am not certain it will work. I don't recommend routing or cutting the wood unless you're experienced with such a task.

I will look more into our situation and see if I can find any more useful tips or recommendations.
A home owner from Chicago area says:
Thanks for the initial input Paul. I really appreciate it.

In terms of the stick-on weatherstrip you mention, I assume I would place it in a similar position as my cotton batting on both windows (so that two piles would meet up when the windows are closed...forming a good barrier to any pin sized hole)?

I'm a little concerned about the longevity of an adhesive given my last experience. If the painted wood surface is clean, should the adhesive be able to handle the friction from opening and closing? Is there a special technique I'm supposed to use to make the adhesive stick better?

Just thinking out loud...what about using a glue too?

Thanks again for all of your help.

Profile picture of Donna
Donna from SWISCO responded:
Hi Pete,
It is suggested to prepare the surface by cleaning with denatured alcohol.

I added this same stick-on pile weatherstrip to a painted steel surface around the perimeter of my front door because I had air flowing in and now it is a very tight seal. The pile has not peeled up at all and I open an close my front door several times a day and it is really tugging on that weatherstrip.

I would definitely recommend trying it.
Reply to Thread
Use this form to ask a follow-up question or to share your experience regarding this subject.
(your email address will be kept private and is only used to inform you when a response has been made)