If you own your home, you could install a ventilation system with an air-to-air heat exchanger with the outside... that way you at least reduce the heating loss. Or you install a forced ventilation towards whatever adjacent room there is, with a foam mesh to pad down on sounds.
Why? You can have a simple indoor exchange for under a hundred dollars - a simple bathroom fan for 20€ would be a starter if you don't mind its noise, but stuff like axial fans for pot growers is pretty cheap as well (e.g. [1]). That, a 100mm core drill and a fairly simple mechanical 230V switch on the door should be enough.
Because labour is crazy and I don't feel comfortable doing this myself. I've recently had a basic AC unit installed at home, it was £500 for the hardware and then another £1000 on top of that for the installation. I imagine that exchange fan would be at least £1000 installed and I just don't have a grand laying around spare to do this.
Yeah, AC units do require a lot of specialized labor to install (in some jurisdictions, it actually may even be mandated by law)... but a simple fan? That's half an hour for the drill, half an hour for the electrician and that's it.
