Adhesive/"seal"er

need to seal vents. Rather not use chemical since they are indoor intake/outtake vents.

Paper-mache? Cut up strips of newspaper and use a flour&water paste to glue it into shape. If you add a good bit of salt to the flour, it will make the end product even harder and longer lasting, as with all that salt, it will be less likely to support any mold or bacterial growth on it. And the nice thing about paper-mache is you can paint on it when it has dried.

And welcome to Permies, Ann!