An open entrance door welcomes customers, but it is a weak point for the indoor climate. If you want to size an air curtain correctly, you need to consider more than the width of the door: the actual mounting height, the length of the unit, the right heating type and the installation position are what matter. Choose wrongly and the unit may blow hard, but the air barrier never reaches the floor and the draught remains.
In this guide we show you step by step which criteria to use when choosing a door air curtain. You will learn why the installation height matters more than the door height, how to match the unit length to the door width, when a unit without heating, with electric heating or with a hot water coil makes sense, and which details you should gather for sound planning. The technical values are taken from the data sheets and planning notes of the manufacturer Frico.
How an air curtain works and what sizing depends on
An air curtain blows an even jet of air downwards across the full width of the opening. This jet separates the air inside from the air outside without obstructing people or goods. According to Frico, how strongly air flows through an open door depends on three factors: the temperature difference between inside and outside, the pressure difference between inside and outside, and the wind striking the door opening. The greater these influences, the more stable the air jet needs to be.
This leads to an important planning rule: an air curtain should not be chosen on air volume alone. Frico points out that a unit with plenty of air but an unfavourable flow pattern only protects well directly at the outlet grille, while the effect fades near the floor. What counts is that the airflow reaches the floor at sufficient velocity and evenly across the whole width. If the velocity there is too low, the jet cannot withstand the wind. If it is too high, turbulence develops that reduces the protective effect and raises the noise level.
How much the air velocity drops with distance is illustrated by an example from the data sheet of the compact Frico ADA: averaged across the series according to ISO 27327-1, it is 7.7 m/s at 0.1 m, 4.2 m/s at 1.0 m and 2.8 m/s at 2.5 m from the unit. This is exactly why the manufacturer specifies a recommended mounting height for every series.
Mounting height rather than door height: the key sizing factor
In its selection guide Frico stresses that the installation height, not the height of the entrance, must be considered when choosing a unit. If a unit above a 2.1 m door actually hangs at 2.8 m because of a fanlight or a suspended ceiling, the series must be chosen for those 2.8 m. At the same time the unit should sit as close to the opening as possible. The following overview shows the mounting heights recommended by the manufacturer for selected series from our range. According to Frico, the actual value always depends on the premises.
| Series | Recommended mounting height according to Frico | Installation position | Heating types |
|---|---|---|---|
| PA1508 | small openings such as kiosks, serving hatches, counters | horizontal | electric |
| PA2200C | entrances up to 2.2 m | horizontal | none, electric, water |
| ADA | 2.5 m | horizontal | no heating |
| Pamir 2500 (PAF) | 2.5 m | horizontal | none, electric, water |
| AR200 | 2.5 m | recessed in the suspended ceiling | none, electric, water |
| PA3200C / AR3200C | 3.2 m (AR3200C with water heating 2.8 m) | horizontal / recessed | none, electric, water |
| Pamir PAFEC | 3.5 m, 4.2 m or 5 m depending on size | horizontal, vertical, recessed | none, electric, water |
| Arden ARFEC | 3.5 m or 4.2 m depending on size | flush with the ceiling | none, electric, water |
| Cordilla G / Ziller G | 4.5 m | horizontal or vertical / flush with the ceiling | none, electric, water |
| Tatra | 6 m | horizontal or vertical | no heating |
If your mounting height lies between two sizes, clarify the choice with a specialist planner or via the product selection tool that Frico offers to planners. Units with EC motors such as the Pamir with stepless airflow control can be finely adjusted for this. In very windy locations or where there is a constant noticeable negative pressure in the building, it is worth consulting a specialist planner, because the right size alone is then not enough.
Combining door width and unit length correctly
The second step is the length. Frico recommends that the air curtain covers the full width of the opening. If the unit is shorter than the door, outside air flows in unhindered at the edges. A flow simulation that Frico published for a Pamir air curtain showed exactly this effect: warm outside air entered the air-conditioned room through a gap between the unit and the wall. Mount the unit as flush as possible with the side boundaries and as close to the opening as possible.
Most series come in fixed lengths, typically 1 m, 1.5 m, 2 m and for some series 2.5 m. For wide openings, Frico says several units are mounted directly next to each other. For a 3 m wide shop door you could therefore combine two units of 1.5 m each, or one 2 m unit and one 1 m unit. Make sure that all units serving one opening are set identically and controlled together.
For very large doors in halls, logistics centres or at loading bays, vertically mounted units are used on both sides of the opening. Frico gives recommended installation widths for these, for example 6.5 m for Cordilla or 8 m for the Tatra industrial air curtain, each with air curtains on both sides. Such solutions should always be planned on a project basis.
Choosing the heating type: no heating, electric or hot water
Air curtains come in three versions. Which one fits depends on the application and on the existing building services. Frico gives a clear rule of thumb: if there is a draught problem, choose an air curtain with heating. The manufacturer recommends units without heating for cold room openings and for air-conditioned rooms. Heated units can be run in fan-only mode in summer to keep cooled air inside.
- No heating (A): simple electrical connection, suitable for cold rooms, air-conditioned areas and internal doors between zones with similar temperatures.
- Electric heating (E): no water pipes required, small units partly on 230 V, larger outputs on 400 V three-phase. For the PA2200C the range runs from 2/3 kW at 230 V to 10/16 kW at 400 V. The electrical connection must be designed by a qualified electrician.
- Water heating (W): connection to the existing heating system. Depending on the series, Frico offers coils for different flow temperatures, for the Pamir for example WH for water from 80 °C, WL up to 80 °C and WLL up to 60 °C.
For water-heated units the stated heat output is always tied to water temperatures. For the Pamir and Arden, Frico specifies it for defined flow and return temperatures such as 60/40 °C at an air inlet temperature of +18 °C. If your heating works at low temperatures, for example with a heat pump, a low-temperature coil is an option. You can read more about why low system temperatures make sense in our guide to flow temperature. According to Frico, water-heated air curtains also need a valve kit that controls the water flow. The principle is similar to a heating coil in a ventilation system.
Installation position: visible, recessed or vertical
The most common solution is horizontal mounting directly above the door with wall brackets or on threaded rods below the ceiling. These units are easy to access and quick to install. Where appearance matters, for instance in boutiques, hotels or banks, recessed units are an option. With the Frico AR, only the underside is visible after installation, sitting flush with the suspended ceiling. Air is drawn in at the underside and blown out towards the entrance.
With recessed mounting you should check early on whether the ceiling void and the substructure are sufficient and whether access for maintenance and cleaning is possible. Frico explicitly points out that the air outlet must remain unobstructed and that access for maintenance work must be considered. For electrically heated units the manufacturer also specifies minimum distances, for example 1,800 mm between outlet and floor for the PA2200C and AR200.
Vertical units stand at the side of the opening and blow horizontally across the width. They are an alternative for tall doors or for entrances without enough space above the door. You will find an overview of horizontal, vertical and recessed models in our air curtains category.
Planning checklist
The more information is available, the more precisely a unit can be selected. For a consultation, Frico lists the following points that you should gather in advance:
- Type and size of the premises, for example shop, office, workshop or warehouse
- Width and height of the opening and the actual mounting height
- How often the door is used or whether it stays open permanently
- Preferred heating type and, for water heating, the available water temperature
- Indoor and outdoor temperature and the wind conditions at the entrance
Also check the ventilation of the building. Frico points out that the pressure difference between inside and outside should not be too great and that balanced ventilation is essential. If a powerful extract system without sufficient supply air draws air out of the building, it pulls outside air in through every opening, and no air curtain can fully compensate for that. For installation, the electrical connection and, for water units, the hydraulic integration, we work with installation partners who can take care of fitting, installation and maintenance on site.
Frequently asked questions
Does the air curtain have to be as long as the door is wide?
It should cover the full width of the opening. If no unit of the right length is available, combine several units side by side. A unit that is too short lets outside air through at the edges.
Which height counts when choosing?
The actual mounting height of the unit, measured from the outlet to the floor. According to Frico it matters more than the height of the door, because the airflow must reach the floor at sufficient velocity.
When is an air curtain without heating enough?
Frico recommends unheated units for cold rooms and air-conditioned rooms. At entrances with draught problems in winter, however, the manufacturer advises a heated unit.
Electric or hot water: which is better?
That depends on the existing systems. If a heating system with a suitable flow temperature is nearby, a water-heated unit with a valve kit is an option. If there is no heating connection or it can only be created with great effort, an electrically heated unit is easier to install.
Conclusion
When sizing an air curtain, start with the actual mounting height and then choose the matching series. The unit length must cover the full door width, and for wide openings several units work side by side. The heating type depends on the application: no heating for cold rooms and air-conditioned areas, electric or water heating against draughts in winter. Balanced building ventilation and clean installation directly at the opening ultimately determine how well it works. You will find suitable Frico units for entrances, counters and doors in our range, for example the air curtain for horizontal mounting in three heating versions.
