If it's your house, you can put your caulk anywhere.
Home Improvement
Home Improvement
I'd try clear silicone. Very easy to work with, won't stain, and pretty easy to peel off if you need to. Won't hurt, will probably help.
Yeah but you’ll need black caulk. You’ll just need to ask around for it.
You'll also definitely want the thickest consistency.
So be sure to ask for thick black caulk.
So I ask the guy at home depot for the longest, thickest, blackest caulk, right?
Is this picture from the exterior? I'm guessing this is a fixed vinyl (as opposed to wood) window?
If it's the exterior, that gap might be for water drainage. If it's the interior it might be for equalizing interior and exterior pressure. I'm doubtful either is the case though.
Filling the gap is likely okay.
This is the interior of a fixed window. Below it is a sliding screen window, then a sliding single pane window, and finally another sliding single pane window.
Unfortunately since these are single pane windows most of the thermal performance issues will be due to the glass. Sealing this gap will help some, but it will be just a drop in the bucket.
Replacing the windows with insulated glass (two pane) windows is ideal. However that will be expensive.
The easiest/cheapest option will be the temporary cling-film type kits you can buy--you won't be able to operate the windows, but that probably won't be an issue in the winter. Properly sized/installed storm windows will help some too, and be significantly cheaper than new windows.
I mean nothing stopping you. Just make sure to use something outdoor/ weather proof.