I've got a Jenn Air stove with a downdraft fan vented to the outside. In
the winter, cold air seeps in from the outside (I do have a louver mounted
on the outside wall). Sometimes when it's really cold you can freeze a
small drop of water on the stovetop. I usually need to put a dishtowel over
the vent which helps a bit.

The Jenn Air website suggests installing something called a 'thermal break'
which is described as a non-metallic (so as not to conduct heat) piece in
the air duct as close as possible to the outside. No one at my local stores
has ever heard of this device.

Does anyone out there know what this looks like and possible where else I
could find one?

Thanks in advance!
KZ