Curious City recently answered, “Why does Chicago have so many revolving doors?” That made us wonder how many people know that using revolving doors saves energy. If you didn’t before, now you can feel a tiny boost of adult pride and child-like glee when you chose the revolving doors; you’re saving energy while you run around in a circle!
Revolving doors are energy efficient?
Yes they are. Primarily because they don’t have to “open” to let someone pass into our out of the building. At every moment, there are two weather stripped arms in contact with the curved door jamb, meaning that air never flows into or out of the building. Neither does snow, rain or sleet. The area of floor that you walk across traps dust and dirt, meaning that entering the building results in less mess to clean up, slippery floors or other debris. Simple and effective.
Another favorite podcast has address this question: 99% Invisible featured Revolving doors in 2013. As they put it,opening a standard door is like “tearing a hole in a building” which lets out a lot of conditioned air that then has to be replaced by the heating or air conditioning system of the building. The podcast quotes a 2006 MIT research problem which studied the two types of doors – swing and revolving – and they found that standard doors exchange eight times a much air as revolving doors! Read it all here.
They are also space saving. The best way to stop air winter air from rushing into a building using swing doors is to set them up on both sides of a vestibule. That takes a lot of space (when you account for ADA accessibility guidelines) and can still fail when someone choses to hold or block open both doors at once. A revolving door takes less room and does the job better.
Per Curious City, revolving doors solved another problem at the time of their invention. We’ve talked about Stack Ventillation in our post on passive cooling. At its most simple, the concept boils down to this: heat rises. In the new tall buildings common in the mid 1800s, hot air rose up elevator and stair shafts, creating suction at the base of the building. Sometimes it was so great that people could pull a swing door open on the ground floor!
Curious City asks a question of its own:
Can you think of another century-old invention that works the same way as it did when it was created, but has only become increasingly relevant?
There’s just one problem … many people don’t use those energy-efficient, revolving doors.
Another question for Curious City – why don’t people USE revolving doors.
Per 99% Invisible, there are a lot of reasons why revolving doors are scary: What if you get stuck in one … what if you go into the compartment with someone else … what if you are superhero and your cape gets caught in a revolving door? Some reasons are less silly: its hard to tell how hard you’ll have to push, they break up conversations etc. There are a lot of rational and irrational fears.
That same MIT Study examined the use of revolving doors vs swing doors in one building on campus and found that the revolving doors got only 25% of traffic. However, they could use simple signage to they could raise that usage to 60%.
Andrew Shea, author of Designing for Social Change, is interviewed in the 99% episode. He repeated the MIT study at a building at Columbia University in New York and observed that a baseline of 28% of people used revolving doors. Then he put up a simple paper sign about the 8x benefit on the swing doors … it caused 58% of people to use the revolving doors. Shea experimented with several versions of signs and when he matched his sign to the Columbia university branding he found a 71% usage of revolving doors.
He’s produced a Revolving Door Action Kit with information and door signage you can apply to swing doors next to revolving doors near you.
What Designers Can Do
For one thing … we can preserve existing revolving doors and keep specifying them in new buildings. We can also work on improvements in design, making them larger, more attractive, and more eye catching. Someone has proposed a revolving door that GENERATES energy when it is turned.
And … what YOU Can Do
Just use the revolving door when you see it and know you’re saving energy in the building and making the world a slightly greener place. Good Job, YOU!