I need to install a duct to vent a kitchen range hood (under cabinet-style) and am wondering if there are any prefab parts that may assist me. The hood has an 8" round and a 6" round outlet. Here are tech specs on the hood: http://www.ventahood.com/images/docs...ifications.pdf
I would like to transition them into a single rectangular duct of the same area (~7" x 11" or ~6" x 12"). This duct will be going through kitchen cabinets, and the rectangular shape will consume less space in the cabinets and will mount more easily to them. The rectangular duct would be run along the top of inside of the cabinets and will still allow the bottom of the cabinets to be used.
So, in summary, how do I go from an 8" round and a 6" round to a 7" x 11" (or 6" x 12") rectangular duct? Are there any parts available that will do this (or close), or does it have to be custom made?