I'm planning use a window type A/C on my little attic room. My A/C unit is just .5 HP, just enough for the small room. The problem is there's no proper exhaust area like the standard Window type. There's an empty space on the side that can be used as space for its backside/exhaust. The empty space is a above the ceiling of the house (not the attic) (the attic is on the 2nd floor used for some storage). The empty space is enclosed within the roof, so no constant "fresh air" coming in. It's used for maintenance way to the roof.
Split type AC are not an option.
I just wanted to use this spare A/C unit. The downside is the exhaust is above the ceiling of the house, but the space is the ceiling is so huge. Even 10+ times bigger than the room. Is this possible? or any downside? I mean the best option was to have a split type Aircon, but for now I want to use the extra A/C for the attic.