The Green Side of Doors
Retailers are beginning to take a new look at an old concept: the revolving door. Approximately 100 years after its invention, the revolving door is generating increased interest in the retail and hospitality industries largely due to its energy-saving potential.
Revolving doors got a big boost from a 2007 study at the Massachusetts Institute of Technology (MIT), which found that, on average, eight times more air is exchanged when a swing door is opened as opposed to a revolving one. Depending on the climate conditions, either warmer or colder air enters the facility, which makes the air conditioners or heaters work more to bring the interior temperatures back to average, resulting in higher energy bills.
The researchers at MIT estimated that if everyone used a revolving door at E25 (one of the research buildings on the campus) instead of the swing doors, MIT could save as much as $7,500 annually in natural gas used to power the buildings and save nearly 15 tons of CO2 emissions.
While the researchers based their study on buildings at MIT, the results are applicable to grocery stores and other larger-footprint retail stores as well, according to many industry experts.
“Whenever air is exchanged between inside and outside, air-conditioning or heating equipment has to work harder, which uses more energy,” said Mike Fisher, VP, Besam Entrance Solutions, an Assa Abloy Group Co., Windsor, N.J.
Bi-parting automatic sliding doors account for the majority of doors in retail stores, Fisher added. Such doors typically provide an opening 6 ft. wide by 7 ft. high.
“Normally, a store would have two of them, with the idea of having an air lock, so that one closes before the other,” Fisher explained. “But in reality, the doors are spaced too close together in most instances for the air lock to exist. The end result is that the outside air blows in, and the conditioned air blows out.”
In contrast, a revolving door is never truly open as the 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. The revolving door stops conditioned air from moving freely whereas with other doors, the air rushes out of the opening. (To maintain accessibility for the handicapped, it is necessary to have at least one sliding or swinging door.)
The Food Emporium, which operates 16 grocery stores throughout Manhattan, recently installed a three-wing revolving door (from Besam) at one of its midtown locations. The grocer is so pleased with the climate control the door is providing, it has specified the door for another location.
In another recent Besam application, the Gaylord Palms Resort, in Kissimmee, Fla., recently installed a 16-ft. diameter, two-wing revolving door. Its two-wing design securely seals entrances when the unit is closed, eliminating the need for costly additional security doors.
Some retailers are put off by the up-front cost of revolving doors, which are much more expensive than bi-parting automatic sliding doors. However, Fisher noted, automatic sliding doors require glass and aluminum between the sliders, an interior ceiling and lighting—all of which are included with a revolving door.
And with the rising cost of energy, the payback on revolving doors is good, often in as little as three years, he said.
“Revolving doors in retail stores are more commonplace in Europe, where operators have been living with high energy costs for some time,” Fisher added.
Revolving doors also generally have higher maintenance costs compared to automatic sliding doors.
“A revolving door really is a moving vestibule and, as such, it requires more maintenance,” Fisher said.
Another issue involves use—or lack of it. Some people will shy away from a revolving door because they are uncertain how to use it.
“Instead, they will use a side door, which defeats the purpose of the revolving door,” Fisher added.
As retailers look for ways to be more sustainable and reduce their carbon footprint, revolving doors are likely to become more commonplace in larger stores.
“A revolving door is really the ultimate green machine,” Fisher said. “It’s made up mainly of glass and aluminum, 50% of which is post-industrial recycled materials.”