Venting an over the range microwave.

[Tim K]

Baths are vented to attics all the time and they are much higher producers of moisture. There is nothing in the building code (last time I looked was 10 years ago) that specifies a vent must go outside. In fact, there is no requirement for a vent at all. I'll agree it's better to go all the way, but roof penetrations are not always simple. I've seen homeowners do it themselves and end up with a leaky roof.

Where are you planning to plug it in? I can't remember if a MW requires a dedicated circuit like a fridge, but I don't think so. They are big draws, however, and if you run one on a circuit that runs other high power devices you'll likely blow breakers.