Overview
- The single best strategy is to prevent heat from entering by airing only at night or early morning and keeping windows closed during hot daytime hours to stop solar and outdoor heat gain.
- External sun protection such as roller shutters, outside blinds, or awnings blocks solar radiation far more effectively than indoor curtains and should be closed before direct sun hits windows.
- Do not rely on permanently tilted (kipp) windows because they let warm air in without meaningful air exchange; use short, wide cross‑vents early or late when outside air is cooler.
- Fans improve comfort by speeding sweat evaporation and can move cooler night air into rooms, but they do not lower actual indoor air temperature and use much less electricity than mobile AC units.
- Meteorologist Jörg Kachelmann adds that ventilation must be situational: rising indoor CO2 or humidity can make short bursts of airing necessary even when outside air is warmer, and only an air conditioner will actually reduce room temperature.