An open shop door tells customers they are welcome. At the same time, warm room air flows out and cold outside air flows in during winter, while cooled air escapes in summer. If you want to save energy with an air curtain in a shop, you should know where the losses at the door come from, which savings are documented and what role the controls play.
In this guide we explain why an open door costs so much heat, what manufacturers and studies say about the effect of air curtains and how to run your unit so that it does not become an energy guzzler itself. We also show which room temperature requirements apply to workplaces near the door and which typical mistakes reduce the effect. We only give specific percentages with a source, because the actual saving always depends on the individual building.
Why an open shop door costs energy
Air flows through an open door as soon as the conditions on either side differ. The manufacturer Frico names three influencing factors: the temperature difference between inside and outside, the pressure difference between inside and outside, and the wind striking the door opening. In a heated shop, warm air flows out at the top of the door while cold air flows in at floor level. That is exactly where customers and staff stand, so the draught is correspondingly unpleasant.
How large this share of the energy demand can be is shown by a study by AMCA (Air Movement and Control Association), summarised by Frico: according to it, infiltrating outside air can account for up to 18 % of the total heat loss in commercial buildings. The share is particularly high at doors that are used frequently, for example in restaurants, retail, supermarkets, offices and hospitals. A shop with customer traffic is therefore a typical application.
There is also an effect that is often overlooked: if the door is frequently open, the heating has to make up for the losses, and thermostats are often turned up or additional heaters used against the draught in the checkout area. The shop as a whole is then heated more than would be necessary without the draught.
What an air curtain can save: documented figures
There are manufacturer statements and studies on the effect of air curtains that need to be put into context. All values are maximum or average values under certain conditions and are no promise for an individual building.
| Source | Statement | Context |
|---|---|---|
| Frico, referring to independent tests | correctly installed air curtains can reduce energy loss at an open door by up to 80 % | open door, correct installation |
| AMCA study, summarised by Frico | air curtains provide about 65 % protection against infiltrating outside air, a vestibule about 23 % | around 350 simulations, entrance with two doors |
| AMCA study, summarised by Frico | lower total energy consumption of a medium-sized office building with an air curtain, both with and without a vestibule | balanced ventilation, on average 100 people per hour |
| AMCA study, summarised by Frico | infiltrating outside air can account for up to 18 % of the heat loss of commercial buildings | commercial buildings in general |
For your shop this means: a correctly selected and installed air curtain can significantly reduce the losses at the door, but the exact order of magnitude depends on door size, opening frequency, wind, temperature difference and building ventilation. Reputable planners therefore calculate with the data for your location rather than with flat percentages. You will find the basics on choosing mounting height, length and heating type in our guide on sizing an air curtain correctly.
Workplaces near the door: what the workplace rules require
In retail the checkout is often right next to the entrance. The German Technical Rules for Workplaces apply to such workplaces. ASR A3.5 Room Temperature sets minimum air temperatures that must be maintained throughout the period of use. For light work while seated it is +20 °C, for light work while standing or walking +19 °C, and for moderate work while standing or walking +17 °C. If these values are not reached despite exhausting the technical options, the rule provides for additional measures in a fixed order of priority, starting with workplace-related technical measures.
Draughts are covered by ASR A3.6 Ventilation. It describes a draught as a disturbing air movement leading to local cooling and requires that no unreasonable draught occurs in occupied zones. As a guide it states that at +20 °C, a turbulence intensity of 40 % and a mean air velocity below 0.15 m/s, there is usually no unreasonable draught for light work. At an open shop door in winter this value is easily exceeded without protection. An air curtain is therefore not only a question of heating costs but also of occupational health and safety. The assessment in the individual case is made as part of the risk assessment.
Controls determine consumption
An air curtain itself uses energy: electricity for the fans and, for heated units, heat from an electric coil or heating water. Whether the unit pays off in energy terms therefore depends largely on its controls. Frico writes that how effective an air curtain is and how much energy it can save depends largely on the control system, because many influences change constantly, for instance when the sun goes behind clouds, the room fills up or the door is opened.
Modern controls offer a range of functions for this. According to the manufacturer, Frico's FC control system includes temperature-based output control, a weekly programme, heating lock-out with an outdoor sensor, a ventilation mode and a timer. The FC Smart version adds a door contact, app operation and optional wireless sensors. Simpler solutions such as the SIRe Competent control detect via a door contact whether the door is open or closed and offer separate modes for frequently opened and permanently open doors.
- Door contact: the unit runs at a low setting or switches off when the door is closed and only increases output when it opens.
- Outdoor sensor: in mild outdoor temperatures the air curtain's heating is locked out and the unit runs with the fan only or not at all.
- Time programme: the unit stays off outside opening hours.
- Stepless EC fans: the speed can be matched precisely to the situation instead of running permanently at the highest setting.
With the units themselves, it is worth looking at the motor. Frico has published a flow simulation for a Pamir air curtain with EC fans. According to it, the new series is as effective as the predecessor series with AC fans despite a lower airflow, with reduced operating costs. For typical shop entrances with a 2.5 m mounting height, the slim Pamir 2500 air curtain, for example, is intended, available without heating, with electric or with water heating.
Heating type in the shop: electric, hot water or summer mode
If the shop has a hot water heating system, a water-heated air curtain can be connected to it. The heat then comes from the same source as the rest of the space heating. It is important that the coil matches the available flow temperature. Frico offers low-temperature coils for several series, for the Pamir for example the WLL version for water up to 60 °C. According to the manufacturer, water-heated units need a valve kit through which the controls regulate the water flow.
If there is no heating connection near the door, an electrically heated unit is easier to install. Here it is particularly worthwhile to limit the heat output via door contact, room sensor and outdoor sensor, because electricity is expensive as a heating energy. In summer, according to Frico, a heated air curtain can run in fan-only mode to keep air-conditioned air in the shop. You can read how to reduce the energy consumption of your building services overall in our guide to reducing energy costs.
Typical mistakes that prevent savings
In practice, the effect rarely fails because of the unit, but usually because of planning or operation. You should check these points:
- Unit too short: if the air curtain does not cover the full door width, outside air flows in at the edges. In the simulation published by Frico, warm air entered the room through a gap between the unit and the wall.
- Wrong size: if the unit is too weak for the mounting height, the air jet does not reach the floor. If it is set too high, Frico says turbulence develops that impairs the protective effect and the noise level.
- Unbalanced ventilation: if an extract system creates negative pressure in the shop, it draws outside air through the door. Frico explicitly names balanced ventilation as a prerequisite.
- Continuous operation at full output: without a door contact, time programme and outdoor sensor, the unit also runs when it is not needed.
- Lack of maintenance: dirty intake grilles reduce the airflow. According to Frico, maintenance is minimal and is usually limited to regular cleaning and checks.
For installation, electrical connection and, where applicable, integration into the heating system, we work with installation partners who can take care of fitting, installation and maintenance on site.
Frequently asked questions
How much energy does an air curtain save in a shop?
That can only be calculated for the specific location. Referring to independent tests, Frico states a reduction of energy loss at an open door of up to 80 % with correct installation. How much of that applies in your shop depends on door size, opening hours, wind and ventilation.
Is an air curtain better than a vestibule?
In the AMCA study summarised by Frico, an air curtain provided about 65 % protection against infiltrating outside air and a vestibule about 23 %. An air curtain also needs less space. In buildings with a vestibule, an air curtain can be used in addition.
Does the air curtain have to run all day?
No. With a door contact, time programme and outdoor sensor it only runs at full output when the door is open and it is cold outside. With the door closed it can switch off or continue at a low setting.
Does an air curtain help in summer too?
Yes, in air-conditioned shops. According to Frico, units in fan mode keep cooled air in the room. The manufacturer also says the air barrier keeps out insects, dust and exhaust fumes.
Conclusion
A lot of heat is lost at an open shop door, and draughts are a burden for staff and customers. According to manufacturer and study data, an air curtain can significantly reduce these losses if it suits the mounting height, covers the full door width and the building is ventilated in a balanced way. Controls with door contact, outdoor sensor and time programme have the greatest influence on consumption. So always plan the unit and the controls together and calculate with the data for your location. You will find suitable Frico units and controls in our air curtains category.
