Overview
- Leaving radiators on during airing makes thermostats chase the set temperature and effectively heat outdoors, according to Stadtwerke München expert Bettina Hess.
- Suggested window‑open times vary by season: roughly 3–10 minutes in winter, 10–20 minutes in spring and autumn, and 20–30 minutes in summer.
- Ventilate at least twice daily if away or about four times when home, with extra airing after every shower or cooking session.
- For bedrooms in winter, experts recommend morning double airing: ventilate with heating off, reheat for about 20 minutes, then air again.
- Keep rooms at or above about 16°C to lower mold risk as warmer air holds more moisture, and note that poor technique can add roughly 10% to annual heating costs.