There will be a larger gap behind those strips. That is an interior "molding" that is designed to help conceal the irregularities in the drywall jamb return.

Your best seal, would to be to go buy a storm window and put that, on that window, rather than risk damaging the window. If its that bad, you could also use window plastic to seal from inside.

+1.

- A storm window is not advisable as it could ruin your window entirely.

-The part in question is not part of the window. As WoW explained, those are interior moulding/extender strips. They are generally attached with two sided tape that's very durable when properly prepped.

You have a few options on trying to fix:

1) If possible, call the company that installed and have them fix it

2) If they aren't available, try to reset those that are loose with some silicone. This method has mixed results.

3) Ditch them and replace with new "interior stops", this is often shoe or cove molding. This can be messy in trying to remove the two-sided tape in the areas that it did adhere well.

Its not likely that the window is tight enough to cover the gap underneath these with caulk alone, otherwise it would've been done in the first place.

Lastly, know that these pieces are aesthetic and really not sealing anything. If you rmeove them you can probably check and/or double up on the low expansion, closed cell window foam that should be behind them sealing the perimeter of the install.

Peal one off and post a picture of what's underneath.

@HomeSealed Exteriors, LLC @PPF.@Windows on Washington Ltd

I didn't peel off completely, but hopefully it helps.

It looks like there is up to a half inch gap in some areas that just seem open to the inside of the wall. I assume this is impacting insulation significantly.

Is the best suggestion to remove these, add insulating foam, then put new ones on top?