Revolving Door Energy Savings: Do Revolving Doors Save Energy?

Revolving door energy savings are the main reason building owners choose a revolving entrance over a sliding one. The idea is simple: a revolving door is never fully open. Its wings always close the drum against the street, so the air inside the building stays inside, whether it has been cooled at great expense or heated through a Highveld winter. But revolving door energy savings are not automatic, and they are not the same in every building.

This guide explains how revolving door energy savings actually work, when they are worth having in South Africa, when a sliding door or vestibule is the better choice, and how to compare them honestly. It uses our MC-R30 automatic revolving door, which covers diameters from 2,000 to 3,800 mm in three or four wings, with the height made to the opening.

Do revolving doors save energy?

Yes, in the right building. A revolving door saves energy by stopping air flowing straight through the entrance. A sliding door opens a clear path from the street to the lobby every time someone walks through. Wind and pressure differences push air through that path for as long as the door is open. A revolving door never opens that path. Air only moves in the small amount carried round in each compartment.

Whether that adds up to meaningful revolving door energy savings depends on three things: how hard the building is working to heat or cool the lobby, how strongly air is being pushed through the entrance, and how many people use it. A busy, tall, air-conditioned lobby on a windy street is the best case. A quiet single-storey shop on a sheltered street is the worst.

Where the air goes through an open door

Two forces push air through an open entrance, and both matter for revolving door energy savings.

• Wind. Wind against a building’s face creates pressure at the entrance. When a door opens, air is pushed through. On exposed coastal sites such as the Cape Town foreshore, Gqeberha and Durban’s beachfront, this is the dominant force.
• Stack effect. In a tall building, the difference between inside and outside temperature makes air rise inside or fall, pulling air in or pushing it out at ground level. The taller the building and the bigger the temperature difference, the stronger the pull at the lobby door.

Both forces are strongest exactly where revolving door energy savings are greatest: tall buildings, exposed streets and lobbies that are heated or cooled hard. A low building on a sheltered street sees little of either, so a sliding door with good settings may lose very little air anyway.

A worked illustration

The figures below are arithmetic to show the scale of the difference, not measurements from a building. Air speeds through real doorways vary with wind and stack effect from moment to moment.

• A sliding door opening 2,000 mm wide and 2,400 mm high has an area of 4.8 m². If air moves through it at an average of 0.5 m/s for five seconds per opening, about 12 m³ of air passes. At 1 m/s, about 24 m³.
• A revolving door 2,400 mm in diameter and 2,400 mm high holds about 10.9 m³ of air in the whole drum. With four wings, each compartment holds about 2.7 m³. With three wings, about 3.6 m³.

At most, a revolving door exchanges roughly one compartment of air per person, and usually less. A sliding door can exchange several times that every time it opens in a breeze. That gap, repeated thousands of times a day, is where revolving door energy savings come from.

Revolving door energy savings in South African climates

South Africa does not have the long, cold winters that made revolving doors standard in northern cities, but it has three conditions that make them worth considering.

• Coastal humidity and heat. In Durban and Umhlanga, air-conditioning works hard all year to take heat and moisture out of the air. Every cubic metre of warm, wet air that blows into the lobby has to be cooled and dried again.
• Wind. On the Cape and Eastern Cape coasts, wind pushes air through open doors with real force and loads sliding leaves while they move.
• Highveld winters. In Johannesburg and Pretoria, heated lobbies lose warm air quickly on cold, still mornings through stack effect in taller buildings.

Our guide to outdoor automatic doors and the South African climate covers each region in more detail.

Three wings or four

The number of wings changes both throughput and revolving door energy performance. Three wings give fewer, larger compartments that suit luggage, trolleys and people walking in pairs. Four wings give more, smaller compartments, and more wings are always touching the drum walls, so the seal against the street is better. For the best revolving door energy savings, four wings at a mid-range diameter are the usual choice. Where luggage and trolleys dominate, three wings may be better even at some cost in sealing.

Our guide to revolving door dimensions explains how diameter and wing count change the compartment size.

When a revolving door is not the answer

Revolving door energy savings do not justify a revolving door everywhere. These are the cases where we usually recommend something else.

• Low traffic. A sliding door that opens a few dozen times a day loses little air. The saving will not justify the cost.
• Trolleys, beds and large groups. Shopping centres and hospital main entrances usually need a sliding door for throughput and size, sometimes alongside a revolving door.
• Accessibility. A revolving door always needs an accessible door alongside it, usually a sliding or swing door, for wheelchair users, prams and people who cannot use a moving compartment.
• Escape routes. Where the entrance is also an escape route, the fire strategy decides what is needed, and a revolving door usually has to be supplemented by a door that can serve as an exit.
• Tight spaces. A revolving door needs a drum diameter plus approach space inside and out.

Alternatives that also save energy

Where a revolving door does not fit, other approaches capture part of the same revolving door energy benefit.

• Interlocked vestibule. Two sliding doors with a lobby between them, interlocked so only one opens at a time, stop the straight air path. The MC-125 supports two-door interlocking. See our door interlocking system guide.
• Half-open mode. The MC-125 can open the entrance to a fraction of its width during quiet periods, cutting heating and cooling losses without locking anybody out.
• Better settings. A shorter hold-open time and detection that ignores passers-by stop the door opening when nobody needs it. See automatic door speed.
• A canopy or recess. Shelter from the wind reduces the pressure pushing air through the opening.

Comparing the options honestly

We do not publish a general percentage for revolving door energy savings, because the honest answer depends on the building’s height, exposure, traffic and air-conditioning load. Anyone quoting a single figure for every building is guessing. What we can do is look at the entrance, the traffic and the exposure and tell you which of a revolving door, a vestibule, half-open mode or better settings will make the biggest difference for the money.

It also helps to look at the whole entrance, not just the door. A lobby with a second, internal set of doors, a deep canopy or a reception desk set well back from the entrance already loses less air than one that opens straight onto the street, and the extra benefit of a revolving door is smaller there. A shallow lobby facing the prevailing wind is the opposite.

Where a building has an energy model or a mechanical engineer, the door choice can be fed into it. That is the right place to put a number on revolving door energy savings for a specific project.

Revolving doors and comfort

Revolving door energy savings are not the only benefit. A revolving door also keeps wind, dust, street noise and rain out of the lobby, so reception staff are not working in a draught and the floor near the entrance stays dry. On windy coastal sites, that comfort benefit is often what convinces building owners, with revolving door energy savings as a bonus.

Revolving doors also control how people enter. The flow is steady and one-way per compartment, which suits hotels, offices and airports. Our automatic revolving doors page and hotel automatic doors guide explain the options.

Safety and speed

Speed has little effect on revolving door energy losses but a big effect on safety. An automatic revolving door turns at a speed set for the people using it and slows or stops when someone is too close to a wing. The MC-R30 has anti-pinch sensing on the wings. Speed is set on site, and a slower speed suits entrances used by older people or visitors with luggage. See our guides to automatic door safety requirements and the South African Bureau of Standards for standards.

Servicing for lasting savings

Revolving door energy savings depend on the seals and brushes that close the gap between the wings and the drum. Worn brushes leak air, so they are checked and replaced as part of servicing. As standard we service every six months, more often on busy entrances, with the sensing, speed, brushes and drive checked on every visit. See automatic door servicing.

Common myths

• “A revolving door saves energy by itself.” Revolving door energy savings only happen if people use it. If the accessible door alongside is left open, or most people prefer it, the saving disappears. Signage, layout and settings matter.
• “Revolving doors are only for cold countries.” In South Africa the larger cost is often cooling, especially on humid coasts, and that air is just as expensive to replace.
• “Bigger is better.” A larger drum moves more people but holds more air per compartment. Size it for the traffic, not for show.
• “A revolving door generates electricity.” Search engines suggest it, but that is a novelty, not something to plan a building around. The real benefit is the air it keeps in.

Power cuts and revolving doors

When the power goes, an automatic revolving door needs a defined behaviour like any other entrance, decided with the fire strategy. The accessible sliding or swing door alongside needs one too. Where people must keep entering during load shedding, battery backup on that door matters as much as on the revolving door. See automatic doors and load shedding.

Revolving door energy by building type

The case for a revolving door changes with the building. These are the patterns we see most often.

• Office towers. The strongest case for revolving door energy savings: tall buildings with strong stack effect, conditioned lobbies, steady traffic and a reception that suffers in a draught.
• Hotels. A strong case on exposed coastal sites, with three wings often chosen for luggage and a sliding door alongside for groups and trolleys.
• Airports and transport. Revolving door energy savings are real, but throughput and trolleys usually mean large sliding doors carry most of the traffic. See airport automatic doors.
• Shopping centres. Usually sliding doors, because of trolleys and prams, sometimes with a revolving door beside them for foot traffic on windy entrances.
• Hospitals. Main entrances are usually sliding for beds and wheelchairs. Revolving door energy savings matter less than access here.
• Small offices and shops. Rarely worth it. Better settings and a canopy capture most of the saving.

Planning a revolving entrance

A revolving door takes more floor space than a sliding door of similar capacity. It needs the drum diameter, the walls around it, approach space inside and out where people queue and step in, and space for the accessible door alongside. On a new building that is planned from the start. On an existing building, the lobby layout often decides whether it fits at all.

The height is made to the opening on the MC-R30, so tall lobbies do not need a fixed panel above a standard drum. A canopy above the drum keeps rain off the top. We measure the opening and approach space on site before confirming a size, because revolving door energy savings are wasted if people queue outside in the wind because the drum is too small.

Night locking and security

When the building closes, the revolving door can stop with its wings positioned to close the drum, and night locking secures it. The accessible door alongside is locked or placed under access control on the same schedule. That gives a building one secure, sealed entrance overnight rather than a sliding door that relies on its lock alone. See automatic door access control.

What to send us

To give you a useful answer on whether a revolving door is worth it, send photographs of the entrance from inside and outside, the lobby layout, the building height, which way the entrance faces, rough daily traffic and whether the lobby is air-conditioned or heated. With those we can compare a revolving door, an interlocked vestibule and better sliding-door settings, and tell you where the revolving door energy savings are likely to be largest.

Revolving door energy: quick answers

• Revolving door energy savings come from never opening a straight air path to the street.
• Revolving door energy savings are greatest in tall, busy, air-conditioned lobbies on exposed streets.
• Revolving door energy savings are small on low-traffic, sheltered entrances.
• Revolving door energy performance is better with four wings than three, at some cost in throughput.
• Revolving door energy savings depend on brushes and seals, which are checked at every service.
• Revolving door energy savings can be partly matched by an interlocked vestibule or half-open mode.
• Revolving door energy savings should be estimated per building, not quoted as one figure for all.

Revolving door energy questions

Wondering whether a revolving door would pay for itself in your lobby? Request a quote with photographs of the entrance, its exposure and the traffic, and we will tell you which option makes the biggest difference. We are on 010 412 0062, Monday to Thursday 08:00 to 16:30 and Friday 08:00 to 14:00.