We are in the process is renovating our kitchen. One of the things we are doing is installing a more modern range hood instead of the older under cabinet hood. The new hood requires us to create a new vent hole and so our problem is "how do we close and permanently seal the old vent hole on the outside which was much lower?" Especially on the outside - can I cover it with wood and then siding or are kits made for this task?
The 'ducting area' of most hardware stores will carry caps that fit over common sizes of duct. Buy one for the interior and seal it in with silicon as close to the outer wall as possible. On the outside these vents are almost always covered with a downward angled cover. Just spray in "large crack foam" and you may not even need to move the cover. I wouldn't even bother to conceal the outer cover, houses have these kinds of covers all over.