aside from a lintle, you should also consider the width of the wall, and how
that will affect the air movement in the ac housing.
when they are window mounted, there are narrow window frames/sills for the
ac to rest on, giving some space for air flow.
you may need to add similar structure for air flow.

wrote in message
oups.com...
I have an attached garage with cement block outside wall that I would
like to cut a hole in large enough for a 15,000 - 20,000 btu window
a/c. Feasible??