It is surprisingly quiet. I couldn't believe it. Our little 12-volt oscillating fan is louder.
It has heating, cooling and "fan only." It comes with two ducts (shown above) as well as two adapters which I screwed to the plywood insert in the door, replacing the screen in our Yoder Toter 5X8. A drill bit is supplied to drill holes of an appropriate size.
It does lend itself to both interior (permanent) and exterior (temporary) installation. We opted for the second option, and will install ducting from below the galley hatch up through the galley, then a 90 degree turn into the cabin. It has both supply and return lines. Sonetpro installed this unit inside
his FishInn - sans cove - and has pictures in his album.
Ideally, for this type installation, you would be better served to have the unit on hand when building, so that you might customize your tear to accomodate its exact size. See also Sonetpro's venting solution, using a boat vent. Slick!
Marvin the Cool (and Warm)