Door air curtains:
save money quickly with a comfortable indoor climate

Simulations and calculations show how your hall is effectively protected against the ingress of cold air

Who’s not experienced the flow of warm air coming from above open doors or doorways? Door air curtains are being used there. It is inevitable that doorways are frequently opened and closed, or even remain open for longer, particularly in the industrial sector. Door air curtains are the units of choice in these cases to efficiently protect doorways during the winter months from the ingress of cold air, and retain the valuable heat indoors.

How do door air curtains work
and how do they prevent the uncontrolled exchange of air?

An open hall door without a door air curtain can be divided into three zones:

> Upper third: Warm air flows outside. As soon as the doorway is opened, the warm indoor air escapes outside because of thermal up-currents and its lower density.

> Lower third: Cold air flows inwards. Cold air has a higher density and so is heavier than warm air. It therefore flows into the hall at floor level.

> Middle third: The air flows cancel each other out. This is a neutral zone.

ProtecTor EC door air curtains simultaneously work with two air streams to efficiently screen cold air. This patented mode of action, consisting of an ambient and warm air curtain, ensures that the conditioned indoor air is effectively screened.

More information on the ProtecTor

The unheated ambient curtain on the door side comes into contact with the outside air and prevents major air turbulence with the discharged warm air curtain.

The ambient air curtain has a large penetration depth and also pulls the warm air curtain downwards, due to the minimal thermal up-current.

The discharge nozzle of the ProtecTor compresses and accelerates the outlet volume.

This results in a high exit velocity and an associated high pulse rate of the air, which thereby reaches the ground. The air discharge height of the ProtecTor door air curtain is 3.5 - 4.5 m. The unit is fitted with energy-saving EC fans to guide the air through the unit.

To save even more energy, operate the door air curtain in conjunction with a heat pump at low water temperatures. This also has a beneficial effect on the warm air curtain, which reaches the floor more efficiently due to even lower temperature differences.

Simulation showing the flow of cold air with and without door air curtain

Our simulation contrasts an unprotected open hall doorway with a doorway protected by a door air curtain. It can clearly be seen how the cold air flows unhindered into the interior of the hall and spreads out there. The door air curtain works to combat this. In slow motion, we can see how it shields the cold air and protects the hall from losing energy.

Without door air curtain

Time-lapse side view

Plan view

With a door air curtain

Slow motion side view

Calculation using a hall heating tool

Our hall heating tool lets you calculate the heating load of your hall in just a matter of clicks. The calculation results compare the outcome (with or without a door air curtain). Significant differences in the calculated heating load and the annual heat requirement are discernible, a factor that will also ultimately hit your pocket.

Calculation basis

> Hall dimensions: 50 x 25 x 8 m (length x width x height)
> Doorway dimensions: 3 doorways, each measuring 3 x 4 m (width x height)
> Doorway opening time: 5 min/h
> Wind speed: 3.4 m/s (average wind speed at this location)
> Minimum outside temperature: -6.1 °C

The total heat requirement increases by almost 20 % if no door air curtain is used. The use of three ProtecTor door air curtains saves €6,882 in energy costs per year. This justifies the investment after only a very short time.

21,507 kWh/year * €0.32/kWh = €6,882 cost savings/year

Simply calculate the heating load

Hall heating tool

In just a few clicks, the tool calculates the heating load and the annual heat requirement of halls of any size. Optionally, we would be happy to send you a tailor-made system solution including quotation – quickly and easily.

Try it out now


Depending on the use and design of the hall, you can also decide whether you want to install the ProtecTor with or without a heat exchanger.

Use of the ProtecTor with heat exchanger: There are always comfort factors that come into play when considering the use of a heat exchanger. Do you wish to site workstations closer to the doorway in your hall layout? Not a problem. Comfort is thus ensured close to the doorway or loading zone.

Without heat exchanger: In this scenario, the door air curtain is operated as a pure recirculation air unit, which works isothermically, that is with unheated room air. The room air is simply drawn in and discharged through the outlet nozzle. The cold outside air is reliably screened. The pulse of the discharged air is the decisive factor for the correct operation of the door air curtain.

Conclusion: A door air curtain every time!

The use of door air curtains combines several advantages outlined once again here at a glance:


Energy efficiency

No heat loss in cold months

Prevents warm outside air from entering in summer (operation without heat supply)

Considerable energy savings


Stable hall climate

No temperature fluctuations due to an uncontrolled air flow

An even indoor climate is important for sensitive production processes

Preventing drafts makes it possible to site workplaces closer to the entrance area

Improved use of the indoor space


Increases employee productivity

Pleasant, stable room climate for a comfortable working environment

Positive impact on employees’ productivity and well-being (health maintenance)

Ask us for advice. Together we’ll find the optimum solution to meet your needs!