Comment on energy efficiency of air curtains

By Steve Brown, Development Director, Envirotec

A common misconception regarding the use of door curtains in retail environments is that they always use large amounts of energy. This does not have to be the case.

The most important aspect of an air curtain is the barrier of air it creates between the external and internal environments and not its heat output. I will explain why this is important.

No Air Curtain

Warm air naturally rises and when a heated space is subjected to a lower temperature, such as when a door is opened, the warm internal air rushes to escape out of the top of the doorway. This escape of warm air is made up by cold air rushing in at the bottom of the entrance effectively lowering the temperature of the heated space.

The main aim of an air curtain is to reduce this effect by forcing the escaping warm air downwards and back in to the heated space thus reducing the cooling effect of cold air ingress.

A correctly specified air curtain will help improve energy efficiency, compared to doors that are continually opening and exposing the interior of the shop to outside temperatures.

An air curtain creates a barrier that helps prevent the cold outside air from mixing with the warm indoor air. Air curtains with intelligent controls can be configured to contribute to the heating of the interior of the shop, so the energy consumption of the main heating system could be reduced in proportion to the energy consumed by the air curtain.

Air Curtain Fitted

A crucial factor here is that the air curtain should be correctly specified for the doorway it is protecting, with the span of the warm air jet being wider than the doorway. It is also worth noting that many air curtains now use low carbon, low energy heat sources such as heat pumps, thus improving energy efficiency even more.

Air Curtain with heat pump 

The same principles apply to shops that are air conditioned in the summer, as an air curtain will prevent the cooled air from inside the shop being wasted through the doorway.

Closed doors, with no additional protection, which are constantly being opened during periods of high footfall, actually reduce energy efficiency due to the conditioned air leaving the building as explained above.

Therefore, the ideal solution for balancing the requirements of access and energy efficiency is to operate a closed door policy with an integrated correctly specified air curtain, using an efficient heat source, which becomes active when the door is opened.