My problem if a difficult layout for converting the recirculating cooktop vent to exhaust to the exterior? We just moved into our 2007 home and want the exterior vent. The vent hood is on an interior wall with the laundry on the other side. The master bath is right upstairs. Looks like the water supply for the laundry is in one of the stud bays behind the vent hood. Don't know if there is a bay clear for installing a vent. Assume that the water supply and drain for the bath routes through the wall close by, if not in the same bay. There is a finished attic and an HVAC unit above the 2nd floor bath so I assume that routing through to the roof is not an option. One path is through into the laundry room, then run to the outside wall - not the best. Another path if acceptable would be through the wall down into the crawl space and then outside. Through the crawl space is the longest path but has an acceptable equivelent length for the fan. I would reroute some water/drain lines to route the vent properly. What suggestions and advice can you offer?