General Assist Operating Guide

Should I Leave Doors or Windows Open While Using My Air Conditioner?

Quick Answer
For normal heating or cooling, keep external doors and windows closed. Air conditioners are designed to condition an enclosed space, and open doors or windows allow conditioned air to escape while introducing warm, cold or humid outdoor air.

Why Doors and Windows Should Stay Closed

Air conditioners work by repeatedly circulating and conditioning the air inside the room. When doors or windows are left open, the unit must continually compensate for outdoor air entering the space.

This can result in:

  • Reduced efficiency and higher energy consumption.
  • Longer run times, increasing unnecessary operating load.
  • Inconsistent comfort because the room may struggle to reach or maintain the selected temperature.
  • Higher indoor humidity during cooling operation in humid conditions.

For Best Performance

  • Keep external doors and windows closed while the air conditioner is operating.
  • Close blinds or curtains where practical to reduce heat gain from direct sunlight.
  • Ensure doors to spaces you do not intend to condition are closed where this suits the system design.
  • Maintain appropriate insulation and weather sealing to reduce unwanted heat transfer.
  • If fresh air is required, use a dedicated ventilation or fresh-air system where one is installed.
Important
An air conditioner generally does not provide ventilation unless a separate fresh-air or ventilation function has been specifically installed. Closing windows and doors for efficient air-conditioning does not replace any ventilation requirements applicable to the building or space.

Short-Term Ventilation

If you need to introduce fresh air, it is generally better to briefly ventilate the room and then close the doors and windows before resuming normal heating or cooling. This allows the air conditioner to return the space to the desired temperature more efficiently.