AIR CONDITIONING · VENTILATION
Should You Open Windows
While the AC Is Running?
Fresh air and cool air are not the same job. Most homes get a better result when they do them at different times.
The room feels stuffy but it is not yet very hot
Pause cooling and open windows on opposite sides when it is safe and the outdoor air is suitable. A short cross-breeze usually works better than leaving one window slightly open all day.
The AC is actively trying to cool the room
Close the windows. Warm or humid outdoor air makes the system work against a moving target and can make the room feel sticky even when the temperature drops.
Outdoor air is hotter, smokier or more humid
Keep windows closed. Ventilation is not automatically helpful when outdoor conditions are poor. Check local heat, air-quality, pollen and weather information first.
A child will sleep in the room
Ventilate before bedtime when conditions allow, then close the windows and cool the room. Keep direct cold airflow away from the bed and recheck the room rather than relying only on the thermostat.
THE EASY ROUTINE
Air out. Close up. Cool down.
- Check the outdoor air and temperature.
- Ventilate briefly when conditions are suitable.
- Close windows, shade the room and start cooling.
SOURCES & SCOPE
Based on public guidance from the U.S. EPA on indoor ventilation, the EPA on safe home ventilation, and the NHS on keeping homes cool in hot weather. Local weather, building design and equipment vary.