I've got a Whirlpool over-the-range microwave that is currently venting back into the kitchen. I'd like to poke a hole through the wall and vent it directly outside. I've read the instructions and it seems pretty straight forward.
I don't know much about this, so my question(s) is: am I going to be "locked in" to this microwave? What happens in three years when I want to replace it with another brand? Is it likely that the exhaust duct will still line up? What if I replace it with a hood?
There is no standard mounting or vent hole dimensions for these type of microwaves. Although most of them adapt to 4inch vent hose, there is no standard to where on the back of the microwave the vent is attached, and this can effect where you need to cut your hole in the wall, especially in 2X4 walls where you won't have a lot of room to offset the vent.
The fact that there is no standard makes this a problem over and over again, which is why most people just let it vent into their kitchen.
A solution to this might be to vent up and then out. I'm assuming that this is mounted under a cabinet and over the stove (they generally are). Instead of going straight out the wall go up into the cabinet and then through the wall. this up and then out model might give you some play room if you switch to a different microwave or move up to a hood. you loose some storage space doing this but may be worth it.
You can get flexible aluminium hose, which I have used to deal with a situation where the appliance didn't line up with the outlet hole. It is not totally smooth, so there is the potential for a bit of grease build up (you could replace it every now and again, or put it in the dishwasher or something) and it will impair the airflow slightly (run as short a length as you can).