Do air curtains work for shop doors?
Updated 23 October 2026 · SEO Dons Editorial
An air curtain is a fan unit fitted at the head of a doorway that blows a fast, narrow jet of air across the opening. It cuts the exchange of air between inside and out, so it matters most where a door is open for long periods or never closes.
What does an air curtain do at a shop door?
The government-backed Energy Technology List (ETL) describes air curtains as a way to reduce losses by disrupting the natural convection between two adjacent spaces at different temperatures. It says they are typically used where an open door is needed for uninterrupted access, or where traffic is so high that the door stays open for extended periods.
The CIBSE Journal CPD module of March 2026 explains why. Once a door is open, insulation no longer defines the boundary: airflow is set by temperature differences, wind pressure and the building's ventilation, and in busy retail and logistics buildings these flows can dominate heat loss. The air curtain trade group, HEVAC, adds that even under a closed-door policy, enough foot traffic means the entrance effectively becomes open. The retail air conditioning page covers why an open shopfront drives so much of the cooling load.
Do air curtains really work?
They can, when the application suits them. The CIBSE module says there is some evidence of significant energy savings when air curtains are correctly applied, and cites field studies in retail buildings that reported HVAC energy reductions above 30% in high-traffic entrances. Read that as a favourable case, not a forecast for one shop: the module is a sponsored CPD item that credits a figure to an air curtain maker, and it goes on to list how the jet fails. Two more points matter when weighing any saving figure.
- Ask about the test. HEVAC's page names BS ISO 27327-1:2009, a laboratory test that rates airflow, velocity projection, velocity uniformity and fan energy. It lists a proposed part 3 for measuring energy effectiveness at a doorway, so a saving figure needs its own stated basis.
- Part L software will not show it. CIBSE says the standard compliance tool (SBEM) does not explicitly model airflow through open doors or the separation an air curtain creates, so designers enter the unit as a heating or cooling device.
When do air curtains fail?
CIBSE's module says performance comes down to building physics. These are the failure modes it describes.
| Problem | What happens | What to check |
|---|---|---|
| Jet too slow | It loses momentum before the floor, and the unit behaves more like an over-door heater than a barrier | Discharge velocity measured at commissioning |
| Jet too fast | It hits the floor hard, and the turbulence can increase air exchange | Fan speed set, not left at maximum |
| Wrong angle | Most units are installed to discharge 10 to 20 degrees outward from vertical, towards the outside; a different angle is a listed failure mode | Angle set and recorded |
| Negative building pressure | Extract fans draw outdoor air in and can overwhelm the jet | Balance of supply and extract |
| Cross-draughts | Open doors on opposite facades or open roof vents deflect the jet | Other openings in the building |
| Strong wind | Typical units resist modest pressure differences, about 3 to 5 metres per second of wind at the door | How exposed the entrance is |
| Very large opening | Standard products typically cover openings up to about 8 metres wide or high | Whether a custom system is needed |
Comfort is the other test. HSE says small air movements in cool conditions may be perceived as a draught. CIBSE notes that people walking through feel the jet only briefly, that discharge air is typically limited to about 40°C, and that noise near the door can be noticeable if the unit is poorly selected or run too fast.
Should an air curtain go inside or outside the door?
The sources checked describe a unit fitted above the opening, discharging from a slot along the head of the doorway with the jet angled slightly towards the outside. None says to mount it on the outer face, so follow the maker's instructions. Height is the limit that catches people out: one manufacturer's EASYAIR range lists a maximum installation height of 3.7 metres for heated units and 4.7 metres for the unheated version, in widths of 1, 1.5 and 2 metres, and says its units can be mounted horizontally or vertically. Limits differ by model, so check the data sheet against the real opening.
Ambient or heated: which type?
CIBSE says air curtains can use electric heaters, hot-water coils or heat pumps, and that heat pump versions can be more efficient than electric resistance heating because they deliver heat at a higher coefficient of performance (COP). Ambient units, with no heating source, also exist. An ambient unit adds no heat, so people near the door may still feel cold air. A hot-water coil takes heat from the building's heating system, which is covered on the commercial heating systems page.
The ETL lists single-split heat pump driven air curtains that reach a heating COP of at least 3.10 and a cooling energy efficiency ratio of at least 3.20 under standard test conditions, with outlet velocity uniformity of at least 70%, and that use electric heaters only for defrost or heat pump failure.
What does it cost to run? A worked example in kWh
Tariffs differ by site, so this example stays in kWh. Multiply by the rate on your own bill. Every input is an assumption for illustration, not a measurement. Suppose a doorway unit delivers 9 kW of heat for 2,500 hours a year, which is 22,500 kWh of heat.
| Type | Assumption | Electricity for 22,500 kWh of heat |
|---|---|---|
| Electric resistance | COP of 1 | 22,500 kWh |
| Heat pump driven | COP of 3.10, the ETL threshold under test conditions | 7,258 kWh |
| Heat pump driven | COP of 4.0, assumed | 5,625 kWh |
| Ambient, fan only | 0.3 kW of fan power over 2,500 hours | 750 kWh |
The curtain pays only if the heating or cooling energy it keeps in is worth more than the electricity it uses. That saving depends on door size, traffic, wind and temperature difference, and the only published figure checked is the field-study result above. Ask for the calculation in kWh with its assumptions, then price it with your own tariffs. CIBSE adds that older installations often had manual switches and fixed fan speeds, while modern controls use door sensors to start the curtain when the entrance is open and temperature sensors to monitor conditions.
What else cuts losses at an open door?
An air curtain is aimed at doors that must stay open, so ask a designer to compare it with a door that closes. How the shop is heated also changes how much the door matters: CIBSE's radiant heating module says a room with significant infiltration can still hold reasonable operative temperatures with radiant heat, because the radiant input is unaffected by the volume of airflow. The infrared heating guide covers electric panels, and the warehouse heating guide covers large loading doors. Readers weighing options for an open-fronted shop can send an enquiry through the form on this page.
Sources
All pages checked 22 October 2026.
- Energy Technology List (DESNZ): Heat pump driven air curtains, checked 22 October 2026.
- CIBSE Journal: Module 262, Air curtains and doorways as dynamic thermal boundaries (March 2026), and Module 70, radiant heating with low temperature hot water (November 2014), checked 22 October 2026.
- HEVAC, part of FETA: Air Curtain Group, checked 22 October 2026.
- HSE: Thermal comfort, checked 22 October 2026.
- Mark Climate (manufacturer, facts about its own EASYAIR range only): EASYAIR air curtain, checked 22 October 2026.
Common questions
Do air curtains work in summer as well as winter?
They act on the exchange of air, so they apply to cooled spaces as well as heated ones. The ETL describes air curtains as reducing the amount of heating or cooling needed to maintain a space, and lists heat pump versions that can heat or cool the expelled air. Whether the saving is worth the running cost depends on the door, the traffic and the climate.
Is an over-door heater the same as an air curtain?
Not necessarily. CIBSE says a unit whose jet is too weak to reach the floor behaves more like an over-door heater than an aerodynamic barrier. A true air curtain is set up so the jet reaches the floor with enough momentum to resist the pressures across the doorway.
Can an air curtain cope with a very windy doorway?
Only within limits. CIBSE says typical commercial units are designed to resist modest pressure differences, corresponding to wind speeds of around 3 to 5 metres per second at the door. An exposed entrance, or cross-draughts from other openings, can overwhelm the jet.
Do air curtains make a lot of noise?
They contain high-speed fans, and CIBSE says sound levels close to the doorway can be noticeable if the unit is poorly selected or run at excessive speed. Ask for the sound data at the speed the unit will actually use, and check it against the background level in the shop.
Related guides
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