Two designs share a number of similar characteristics. For instance, both travel the dividing line between the interior and the exterior of the home, meaning that all necessary components are contained in a single unit.
Both of these use the indoor and outdoor air to function. Both are capable of conditioning just one room. But there are a few differences as well.
Windows tend to be very thin and the sleeves for window units are created to benefit from this. These options sit on the sill with the window shut down on top of the case to seal it.
Side panels are used to fill in any gaps that exist. These tend to be quite thin as well and thus, a lot of the sleeve is outside and uncovered. This means that ventilation louvers can be placed n the top and the sides of the machine for free air flow.
This is the major difference between these two distinct types. With a wide availability of louver space there is plenty of room for air movement and this means that these units can be very powerful, all the way up to 36000 BTU or 3 tons. Thus, window air conditioner systems tend to be quite effective in larger spaces.
Conversely, a through wall air conditioner sleeve kit is created for a hole in the wall. Walls tend to be far thicker than windows. Walls that have sheet style siding could be just 6 inches in thickness while stone or brick walls will be far thicker.
Thus, wall AC sleeves will only have louvers for ventilation at the rear in order to ensure that the louvers are not covered by the edge of the wall. This reduces the ventilation space and limits the power of the unit. Wall air conditioning systems do not often go over 14000 BTU, depending upon the model that is used.
Can these be used interchangeably? This question is common when people need ample cooling power in a space that cannot accommodate a window unit. The answer will depend upon the thickness of the wall. Specifications for sleeves provided by some AC manufacturers include the maximum thickness for the wall before a portion of the louvers will be covered.
So what is the major issue if a small portion of the louvers are covered by the wall? There are two issues: 1) the air movement is restricted and this means lower efficiency and 2) these units are very powerful when it comes to pulling in air. Wall edges that are cut could come loose and this will allow loose materials to get sucked into the unit where it could cause damage.
There is one manufacturer, Friedrich, that has made a line of units that have sleeve options. For each model, people can choose different sleeve designs for their individual usage needs.