Jennifer, my OTR mic had to be directly vented from the fan motor straight up through the roof, with a metal baffle covering the opening. Is your roof vent right over the mic fan?

Be careful here...the roof vent you see over your kitchen may be a plumbing vent. If so, you may not connect your hood vent to it.

Essenitally the vent is above the micro area. When the new roof went on, this vent was added specifically for the micro venting, but I haven't run it up yet and have thoughts on how to do, but no actual step by step direcetions.

A new OTR mic will come with installation instructions. You can usually go to the manufacturer's website and download brochures and instruction booklets, too, in case you want to read about it in advance of purchase. It will probably list the supplies you'll need, like flexible ducting, adjustable metal rings, etc. Good luck, it's great to have the mic vented out.

OTR micros connect to rectangular duct at the unit, but as soon as you get into the attic, transition to 7" round , which is a lot easier to work with because you can use adjustable elbows to line the pipe up with the roof jack, most commonly round anyway. Not rocket science, just get the pipe from point A to point B as directly as possible. Screw the joints together with 3 or 4 1/2" self tapping screws and tape with silver foil tape, more costly than regular duct tape, but far superior. Support the duct by wrapping pipe strap aroung it and securing with a couple of screws into the duct, then screw the strapping to a nearby rafter or brace. Be carefull not to bend the flimsy little baffle that is in the flange on the top of the microwave or it will not open. Also be sure the blower unit is directed to flow out the top. Most can blow out the back or top; this is addressed in the installation instructions.