I worked several years designing and installing commercial hvac systems in Switzerland. Plenty of offices, banks, museums etc. have ACs. It’s definitely allowed. But you will need a permit to install a fixed system if it affect/changes the building facade.
The reason why most homes don’t have one is that it’s too expensive for the 3-5 days a year you need it. Especially the new minergy houses can keep cool very well even during summer without an AC.
> Especially the new minergy houses can keep cool very well even during summer without an AC.
Your mileage might vary.
I've personally lived in 2 different "minergie" apartments over the past 2 years (3 summers) and one of them (large, facing away from the sun) was mostly bearable (though I'd still prefer A/C), whereas the other (smaller, facing midday sun) was really hot.
The reason why most homes don’t have one is that it’s too expensive for the 3-5 days a year you need it. Especially the new minergy houses can keep cool very well even during summer without an AC.