How does using the revolving door save energy?
The air that is inside a building has been “conditioned” to make it comfortable for the occupants. We call the equipment that does this “air conditioners” in the summer, but the air heating equipment in use during the winter and ventilation “make-up air” consumed year round is also conditioned air. Energy is required to condition air — to make hot, moist air cold and dry in the summer and to make cold, dry air warm in the winter. Thus, whenever air is exchanged between inside and outside, air conditioning equipment has to work harder, using more energy.
The revolving door stops conditioned air from moving freely. An open swing door is like letting go of a balloon- the air rushes out of the opening. A revolving door is never open- seals remain in contact with the walls of the door at all times. Only the air in the chamber with the person going through the door is transferred.
How much energy does using the revolving door save?
The energy savings from using a revolving door are remarkable, given the three or four seconds over which is occurs. Note that the savings if everyone uses the revolving door don’t amount to 88%, as you might expect from the 8x less air transferred through the revolving door as through the swing doors. That’s because the revolving doors leak more than swing doors, lowering their overall efficiency slightly.
Energy savings depend on the weather- heating is less efficient than cooling and the indoor / outdoor temperature differential is larger in the winter than in the summer, so more energy is saved in the winter. Windy days are worse than calm ones. Still, every time you walk through a door and you feel that rush of “wind,” you’re feeling energy leave the building.
Average heat transfer per swing door passage
- 78 Wh (267 BTU)
- 1.3 hours of light from a desk lamp
- 4.3 hours of light from a compact fluorescent bulb
- Driving a car 306 feet
- Half a mile jog