A Kitchen Bath Designer for 20+ years...still accept jobs occasionally...my experience taught me this:
- If an exhaust fan is not vented to the outside, it is blowing the grease around your kitchen, etc.
- The most efficient venting is that which has the fewest turns and the shortest distance to the outside.
- Microwave over Range exhaust is usually worthless and can be a fire hazard if the exhaust portion is not kept spotless...it is also visually and maybe physically in the way, if placed low enough to work well.
- The quality and size of the exhaust fan is determined by the size and quality of the range.