An expert report for the Rathaus Galerie Essen shopping center shows how differently air curtains and air walls can perform under real operating conditions.
In the case examined, the installed air curtains did not provide sufficient protection against cold air infiltration. The air walls were generally functional, but were installed too far away from the door openings.
The key finding is simple: the decisive factor is not the catalog specification, but the actual airflow performance at the opening.
Air curtains are commonly used to improve comfort in entrance areas and reduce air exchange between indoors and outdoors.
In practice, however, their effectiveness depends heavily on the actual installation conditions. Opening height, wind, temperature differences, equipment position and real airflow performance determine whether enough air velocity still reaches the critical area of the opening.
The operators of Rathaus Galerie Essen were not satisfied with the performance of the installed systems. An independent expert report was therefore commissioned to assess their function, sizing and suitability.
Both air curtains and air walls were examined under real operating conditions. The purpose was not to perform an abstract laboratory comparison, but to determine whether the installed systems were capable of reducing cold air infiltration effectively.
The installed systems were assessed in the actual building environment.
The investigation included:
The decisive question was not simply whether air was coming out of the system.
What mattered was whether sufficient airflow performance still reached the relevant part of the opening to prevent cold outside air from entering the building.
The report reached different conclusions for the two types of systems.
The air walls tested were functional and, in principle, suitable for reducing cold air infiltration. However, in this installation, they had been positioned too far away from the door openings.
This illustrates a key point: an air wall also has to be positioned correctly and designed for the specific opening.
The air curtains examined did not achieve their specified nominal airflow. Under the prevailing cold and windy conditions, they were not sufficiently sized.
Under these circumstances, there was no reliable evidence that they were capable of preventing cold outside air from entering the building effectively.
The result demonstrates why an air curtain should not be evaluated solely based on catalog data.
What matters is the actual airflow performance at the opening.
An air curtain can be suitable for simple entrances, protected openings and applications with limited external influences.
Problems arise when additional factors such as wind, low outside temperatures, pressure differences or unfavorable installation conditions affect the airflow.
In these situations, the airflow directly at the unit is not the only relevant parameter.
The important question is how much usable air velocity and momentum remain at the critical point of the opening.
If the airflow is deflected, becomes turbulent or loses too much velocity before reaching that point, cold air can still enter the building even though the air curtain is operating.
This is one of the key differences between a conventional air curtain and an air wall.
An air wall is designed specifically to separate two air zones. Pressure chamber design, nozzle geometry and discharge direction are used to generate a stable and directed air jet that retains sufficient performance at the critical part of the opening.
More on the technical differences: Air Curtain vs. Air Wall: What Is the Difference?
An air wall is not automatically the better solution for every application.
It does not replace a closed door or a physical barrier, and it also has to be correctly sized and installed.
However, an air wall can offer advantages where a conventional air curtain reaches its practical limits, for example:
The relevant question is therefore not simply:
“Which system moves more air?”
The better question is:
“Which system separates the two air zones more effectively at this particular opening?”
In addition to the expert report comparing air curtains and air walls, tracer gas studies have also been carried out to examine the separation performance of air walls.
These measurements demonstrate that air separation does not have to be evaluated subjectively.
Its effectiveness can be measured.
This is particularly relevant because air movement itself is difficult to see.
Drafts, cold air infiltration or odor migration may be noticeable, but the actual separation performance should ideally be assessed using objective measurements.
A separate tracer gas study investigated how effectively an air wall reduced air exchange between two areas.
The expert report shows that the performance of an air curtain depends heavily on the actual installation conditions.
Catalog specifications alone are not sufficient when wind, low temperatures or unfavorable positioning affect the airflow.
Air walls can provide a technical alternative where a more stable and targeted separation of air zones is required.
However, correct system design remains essential.
Opening dimensions, installation position, temperature differences, wind conditions and the required level of air separation must all be considered together.