A/C
Wallycleaver,
Your right , most a/c units of the type I generally described do sound noisy in motel rooms. If you look in the (Studio Basics 101) leaflet Auralex used to offer to every customer, I think they mention a particular model. I've been in some home brew studios where these units were used and they didn't produce that much noise when installed in a suspension hole using a double layer of Sheetblock. Again, You would typically shut the unit off and seal it off when making actual live passes fo recording. This is simple, but it works.
dom franco,
What you described, using a window unit with ductwork sounds interesting, but I don't see how it could efficiently move the air for any distance within the ductwork( what about the warm air return?). Still, interesting, I'll have to experiment.