Measure the height of the wall opening and subtract the combined thickness of the 2 x 4 s you just cut.
How to put a window ac in a wall.
Measure your a c from left to right including your frame.
Before installing a window ac open the window as far as it goes remove the screen and clean the windowsill glass and window frame.
Window air conditioners often come with a foam insulating strip.
Put those four pieces of 2 x 4 lumber together to make a frame.
Use a utility knife to cut the roll insulation at the top and the bottom of the drywall opening.
Cut two pieces of the c channel in both sizes1 2 and 3 8.
Measure the width of the wall opening and transfer that measurement to 2 2 x 4 s and cut them down to the matching length.
Then cut those down to the matching lengths.
Strictly speaking if you put a window unit in the wall it won t be vented correctly and it can overheat and die or have a shorter lifespan.
With the insulation removed mark the opening corners by drilling through the exterior sheeting with a long drill bit.
Remove the drywall to reveal insulation and the edge of a stud.
Also putting a new window unit in the wall voids its warranty and it will be less efficient i e more costly because you ll have to fill more gaps between the smaller machine and the wall.
Drill hole on the side through channel and coupling than insert a screw.
In the 3 8 c channel insert nut rod coupling on the end.
Measure a 2 by 4 and saw it to fit on top of the cut vertical wall studs at the bottom of the hole.
Cut the strip of foam to the correct length and insert it between the upper window sash and the lower window sash.
Do prepare the window and install brackets if necessary.