House air. I don't recall the store where we bought even offering fresh air but I could be wrong.

Here's a somewhat long article de-bunking the principle: http://www.woodheat.org/the-outdoor-...h-exposed.html

Seems to be a much debated topic. Personally, I don't think houses are built so air-tight that using house air creates a problem. Our house is ICF and supposedly more air tight than a conventional build but we've had no problems getting the stove to run really hot and no noticeable drafts.

Disclaimer...this is only our first wood stove. (Vermont Castings Encore)