Do not switch the AC off. Set it to hold around 24 degrees Celsius, or use a humidity setpoint near 55% if the unit supports one, so it keeps removing moisture while you are away. Leave internal doors and wardrobe doors open, clear the AC condensate drain, move furniture off external walls, and arrange for someone to check the property every week or two.
Key takeaways
- Leave the AC running — hold ~24 °C or a ~55% humidity setpoint.
- Open internal doors and wardrobes so air circulates.
- Clear the condensate drain before you go.
- Have someone check in, run the taps, and confirm the AC still works.
The AC setting
The goal is to keep indoor humidity under control without cooling an empty home to 20 °C. Two good options:
- Hold a moderate temperature — set the thermostat to around 24 °C and leave it. The unit will cycle occasionally and pull moisture out each time.
- Use a humidity setpoint — if your thermostat or split unit has a humidity or “dry” mode with a target, set it near 55%.
Turning the AC fully off for weeks lets the flat warm up and humidity climb to outdoor levels — the classic cause of mold after a vacation.
Airflow and furniture
- Leave all internal doors open so cooled, dried air reaches every room.
- Leave wardrobe, cupboard and store-room doors ajar — these are where mold starts.
- Pull large furniture a few centimetres off external and AC-adjacent walls.
- Do not leave damp laundry, wet towels or full bins in the flat.
Before you lock up
- Have the AC condensate drain checked and cleared, and the filter cleaned.
- Fix any known small leak, however minor.
- Empty and dry the washing machine and dishwasher; wipe out the fridge if you are switching it off.
- Consider a hygrometer you can read remotely, or a small dehumidifier in a known problem room (running alongside the AC).
The check-in
Ask a neighbour, relative or building service to visit every one to two weeks: confirm the AC is still running and cold, run each tap and flush toilets briefly to keep traps full, look for any new damp or smell, and check the area around the AC units. A five-minute visit catches a failed AC or a new leak before it turns into weeks of unchecked growth.
A power cut or an AC breakdown while you are away undoes all of this — which is exactly why the periodic check-in matters as much as the settings.