A:Answer I have used microwaves with exterior venting, and no venting.
When we didn't vent our microwaves the moisture that comes from the interior is vented out into your kitchen. Depending on the make and manufacturer if may vent out the top,bottom etc. But that moisture accumulates in your kitchen and in our case the exhausted moisture vented downward and since heat rises,the underneath surfaces of my upper cabinets was destroyed,as well as the finish of my upper cabinets above the microwave.
This happened with 3 different micro. On the 3rd micro we saw it was going to do the same bad venting into my kitchen, which by the way raises the humidity in your kitchen making it like a sweat box while cooking,it can also cause food smells to stay in your home,staining cabinets and paint and wallpaper., especially if you are into frying foods. When we vented our last two microwaves we no longer had all the nasty problems I noted here. Venting outside is much better, and I will never go with the ventless installation, again. Also going ventless shortened the life of the over the stove mounted microwaves significantly.
I don't care if you spend $100 or $1000, ..even a $100 is a lot of money to waste, when you have to work so hard to earn it.
Hope my honest answer saves some of you trouble and expense.
