Yes, revolving doors are more energy efficient. In a 2006 study conducted by graduate students at MIT, they found that use of a traditional door allowed in 8 times as much air to pass through the building than a revolving door. There was a revolving door in the building, but just 23% of visitors used this door. They concluded that if everyone were to use the revolving door, MIT could save up to $7,500 per year in natural gas.