Keep the doors closed

“Keep exterior doors closed while running your HVAC. It sounds simple, but it will help avoid wasteful loss of heated or cooled air!”

https://www.energystar.gov/buildings/facility-owners-and-managers/existing-buildings/save-energy/stamp-out-energy-waste?fbclid=IwAR3et52ys7nvywsNwC35RzyhgVFRK16i50aO1mFyZl2UCOnL4E4coCMlZgc