How do I seal the space around my "wall" air conditioning unit?

Question

The wall opening is much bigger than the air conditioner itself (the building was build in the 80's when air conditioners were monsterous) now we have this huge gap all the way around the new unit. At present, we stuffed towels all the way around, but this is only temporary since it is pretty ugly.

Answer 1

Any home supply Will have spray foam or you can buy foam strips to do the same.

Answer 2

i have foam rubber on both sides and on the bottom of a window unit.  the foam rubber is about 2 to 2 1/2 wide on both sides and the bottom.  it easy to work with and is cut so it has to be forced in where it needs to go.

Answer 3

Go to Lowes or Home Depot and buy a can or two of expanding spray foam.It'll take care of it.

Answer 4

You can trim off with wood and stuff insulation in the gaps first, the reason for this is if you need to clean or repair the unit do not make the seal to permanent because it will be very difficult to remove for service, I know from experience!  

Answer 5

Fitting in some plywood  or finished vinyl for the outside surface, cut nice and neat.  then insulate with either glass insulation from the inside or spray foam and some finish boarding on the inside around the unit should make it nice and snug and look decent.