everyone's right, none of PLAN on starting a fire... fix the vent with the quilt or styro or both and talk her out of the 'stove quilt'...

Would a layer of vinyl inside help?

Sorry, but this is all kinds of wrong. Putting fabric of any kind on a STOVE TOP is foolish. All it takes is a bump on the knob and the top is on. Venting is insufficient. If its too cold, have her get the vent fixed - don't put newspapers or other flammable materials on top of it!!

Think about how you'd feel if the stove (or your sister!) ever malfunctioned and there was any kind of flamable material on the surface. The whole idea is SO not worth the risk. You need to convince her of that so she doesn't continue to cover the cooktop even if you don't make her a 'stove quilt'.

I think I understand what you are looking for - her cooktop must have a vent right in the cooktop, not in the hood over the top - correct. Lots of cooktops have down draft vents in the surface of them and this must be what she wants to cover up when not using the stove.

I have a cooktop with the downdraft in the center of the cooktop. I don't ever recall getting a draft through there. Maybe the damper is stuck open outside. I hope you can get this resolved.

These are my thoughts, too! I imagine a fire department inspector would come apart at the seams if they were to see something like that. So not worth the risk.

My sister is single, no kids and never I mean never uses her stove, I could see her wanting to cover it with something, I'm not going to give her any ideas tho, that will just mean one more project for me.

If her cook top is like my Jenn Air, there is a vent that is level with and between two glass top burners. The vent goes through the floor and then to the outside wall under the floor (along the basement ceiling). Her idea is a really good one. I've used layers of terry dish towels to cover my vent for years, but now I think I'll borrow her idea and make a cook top quilt, too. Thank your sister for me, please. And, Merry Christmas to all of you!