What Makes an Air Curtain High Performance? Key Specification Factors.

Authoritative guide by Thermoscreens — UK-manufactured air curtain specialists since the very beginning of the technology.

Quick answer: A high-performance air curtain is defined by the balance of three measured forces — velocity, volume and uniformity — delivered with enough throw to reach the floor and form a stable seal across the full width of the opening. Beyond aerodynamics, the specification factors that separate a premium unit from a basic one are heat output, energy efficiency (ErP compliance), acoustic performance, intelligent controls, and independent certification to standards such as ISO 27327-1 and ANSI/AMCA 220.

A high performance air curtain does one job exceptionally well: every time a commercial door opens, it stops conditioned air escaping and uncontrolled outdoor air rushing in. For a busy retail entrance, hospital lobby or industrial loading bay, that exchange happens hundreds of times a day — driving up heating costs, creating cold draughts, and letting in dust, insects and pollutants.

What is a high-performance air curtain?

A high-performance air curtain is a unit engineered to maintain a continuous, uniform jet of air that reaches the floor with enough force to resist the pressure differences acting across the doorway — wind, stack effect and mechanical ventilation — across the full width of the opening, for the full height of the door.

Performance is not a single number. It is the combination of how fast the air moves (velocity), how much air is moving (volume) and how evenly that air is distributed across the nozzle (uniformity). A genuinely high-performance unit gets all three right and proves it with independently tested data.

How does an air curtain actually work?

Air is drawn in through the intake, accelerated by the fan, and pushed into a plenum — a chamber that distributes the airflow evenly along the length of the unit. It then leaves through a narrow discharge nozzle, where directional vanes shape it into a coherent, laminar jet aimed at the floor.

When that jet hits the floor, it splits — part of the air is entrained back inside, part outside. This split is what creates the stable barrier. Get the velocity and volume right, and the split occurs precisely at the threshold, sealing the opening. Get it wrong, and the jet either runs out of energy before it reaches the floor or arrives so hard it bounces back as turbulence and causes the heat loss it was meant to prevent.

(For a deeper visual explainer, see the Thermoscreens resource “How does an air curtain work?“)

What are the key specification factors that define a high-performance air curtain?

These are the factors that genuinely separate premium commercial air curtains from budget units. Use them as a specification checklist.

1. Velocity, volume and uniformity — the performance triad

This is the single most important concept in air curtain specifications, and it is widely misunderstood.

• Velocity is the speed of the air stream. It must arrive at the floor with enough force to “split” and resist door-pressure differences. Discharge (nozzle) velocities typically range from roughly 8–18 m/s depending on door height and exposure.
• Volume is the quantity of air being moved (m³/h). Velocity without volume produces a thin, fragile jet that collapses under pressure.
• Uniformity is how evenly the air is distributed across the entire nozzle width. A jet that is strong in the middle and weak at the edges leaves gaps at the most exposed parts of the doorway.

The international test standard ISO 27327-1:2009 exists precisely to measure these parameters consistently — airflow rate, outlet velocity uniformity, power consumption and air velocity projection — so that ratings can be compared like for like rather than on marketing terms.

Specifier’s tip: Be wary of the headline figure “maximum velocity.” It carries no industry certification and tells you nothing about where that velocity is measured. The meaningful figure is velocity projection — the actual measured speed at defined distances down the airstream.

2. Throw (velocity projection to the floor)

Throw is how far the air stream travels while remaining coherent. For a high-performance air curtain, the throw must exceed the door height — a sensible engineering margin is 10–20% beyond the door height — so the jet still has the energy to split when it reaches the floor.

Under-specifying throw is the most common cause of disappointing real-world performance. A unit rated for a 2.5 m door installed over a 3.5 m opening will never seal it, regardless of how good the data sheet looks.

3. Air separation efficiency

This is the bottom-line outcome: how effectively the unit reduces unwanted air infiltration and exfiltration through the opening. Research published in Building and Environment has worked to link the measurable aerodynamic parameters above to real-world separation effectiveness, confirming that stronger, more uniform jets with minimal degradation produce better climate separation (ScienceDirect, 2019).

4. Heat output and heating type

For heated applications, the unit must add enough warmth to offset the chilled incoming air without overshooting. Specify the heating type to the building’s services:

• Ambient (unheated) — for internal doorways or warm climates where the goal is air separation only.
• Electric — instant, responsive heat; ideal where there is no wet system.
• LPHW (water heated) — connects to the building’s hot-water circuit; the most energy-efficient option for buildings with a boiler or heat-pump plant. Thermoscreens water units are supplied with a motorised three-port valve as standard.

5. Energy efficiency and ErP compliance

A high-performance air curtain saves more energy than it consumes — but only if it is efficient in its own right. Look for:

• ErP compliance (the EU/UK Energy-related Products framework) as a baseline.
• EC fan technology for lower electrical consumption and precise speed control.
• Building Management System (BMS) readiness so the unit only runs when it is needed.

The energy case is well evidenced. Following third-party studies led by Dr Liangzhu Wang at Concordia University, ASHRAE Standard 90.1-2019 accepted AMCA-certified air curtains as a valid alternative to building vestibules. Those studies found air curtain-protected doorways could save 0.3%–2.2% of whole-building annual energy compared with vestibules — equivalent to roughly 1,146–18,986 kWh per year depending on climate zone (Mars Air summary of Wang’s research). Typical payback periods for a well-specified unit fall in the one-to-two-year range.

6. Acoustic performance (dB(A))

In hospitality, healthcare, retail and offices, noise is part of the specification, not an afterthought. A powerful air curtain that is too loud will simply be switched off — at which point its performance is zero. Compare sound pressure levels in dB(A) at a stated distance (e.g. 3 m), and remember that a 10 dB increase is perceived as roughly twice as loud.

7. Controls and BMS integration

Intelligent control is what turns a powerful unit into an efficient one. The best systems modulate fan speed and heat against door state, indoor/outdoor temperature and occupancy. Thermoscreens supplies a touch controller as standard and units that can be linked and managed together, with full BMS integration.

8. Build quality and independent certification

Finally, performance claims are only as good as the testing behind them. Premium units are tested to ISO 27327-1 or ANSI/AMCA Standard 220 (“Laboratory Methods of Testing Air Curtain Units for Aerodynamic Performance Rating”). Certified ratings — rather than self-declared figures — are the closest thing the industry has to a guarantee that the unit will do what the data sheet says.

How do you specify the right air curtain for a doorway?

Even the best unit underperforms if it is wrongly sized. Work through these variables:

• Door height determines the fan type. Cross-flow/tangential units work best up to around 3–3.5 m; centrifugal units handle taller openings of roughly 4–8 m. For exposed, high-traffic or high doorways, a dedicated high-velocity range (such as the Thermoscreens PHV series, suited to doorways up to ~4 m) is the correct choice.
• Door width sets the unit length. Keep a continuous nozzle line across the full opening — gaps between units create weak points where air leaks through.
• Exposure and pressure — wind, stack effect and the building’s own ventilation all push against the jet. The more exposed the entrance, the more throw and impulse you need.
• Mounting — surface-mounted, recessed, horizontal or vertical. Confirm there is adequate space above or beside the door before specifying.
• Application — retail and commercial, industrial, cold storage, healthcare and hospitality each have different priorities (aesthetics, hygiene, robustness, acoustics).

Long-tail takeaway: the right answer to “what air curtain do I need for a high doorway?” or “which air curtain for an exposed retail entrance?” always starts with door dimensions and exposure — never with price.

What is the ROI of a high-performance air curtain?

The return on investment comes from four sources, in roughly this order of value:

1. Reduced heating and cooling demand — the conditioned air stays inside, so plant cycles less.
2. Lower capital and floor-space cost than a vestibule — air curtains free up the square footage a lobby would consume, which is why ASHRAE now accepts them as a vestibule alternative.
3. Improved comfort and productivity — no cold draughts at entrances and tills.
4. Protection of stock and interiors — by excluding dust, fumes, insects and pollutants.

With whole-building energy savings demonstrated in peer-reviewed simulation studies and payback periods commonly inside two years, a correctly specified high-performance air curtain is one of the rare building-services upgrades that pays for itself quickly and improves the occupant experience.

Why specify Thermoscreens air curtains?

Thermoscreens was one of the first companies in the world to design and build air curtains, and today manufactures in the UK and exports to over 50 countries. That heritage matters: air separation performance is the product of decades of refinement in nozzle design, fan selection and control strategy — not something that can be reverse-engineered from a spec sheet.

The Thermoscreens range is built around matching the right unit to the application:

• T Series — the industry standard for commercial and retail, with powerful centrifugal fans and high heat output.
• C Series — including stylish Designer units (horizontal or vertical, any RAL colour or stainless finish) and compact surface-mounted units for restricted spaces.
• PHV — high-velocity units for exposed doorways up to ~4 m, ideal for hotels, airports and commercial buildings.
• HX with Ecopower Air Technology — one of the most advanced, energy-efficient solutions available in the UK.
• Compact 2 — a quiet, cost-effective, easy-to-install solution where space is at a premium.
• Slimline CS Series — a compact cold-store air curtain engineered to maintain climate separation in temperatures as low as -25°C. Built with energy-efficient EC motor technology and built-in frost protection (with heated, enlarged inlet-grille openings to prevent ice build-up), it delivers exceptional performance where headspace above the door is limited — replacing doors and strip curtains while cutting the waste of expensive cold air.

Every unit is ErP compliant and BMS ready, supplied with the Thermoscreens touch controller, and backed by genuine engineering support to get the specification right first time.

Explore the full range: Air curtains by Thermoscreens ·· Case studies 

What makes an air curtain high performance?

A high-performance air curtain delivers the right balance of velocity, volume and uniformity, with enough throw to reach the floor and seal the full width of the opening. It pairs that aerodynamic performance with efficient EC fans, ErP compliance, low noise, intelligent BMS-ready controls, and independent certification to ISO 27327-1 or AMCA 220.

What is the difference between velocity and throw in an air curtain?

Velocity is the speed of the air leaving the nozzle and arriving at the floor. Throw is the distance the air stream travels while staying coherent. A unit can have high velocity but insufficient throw for a tall door — which is why throw should exceed door height by 10–20%.

Do air curtains actually save energy?

Yes. Third-party studies behind ASHRAE Standard 90.1-2019 found air curtains can save roughly 0.3%–2.2% of whole-building annual energy versus vestibules, with payback periods commonly inside one to two years when correctly specified and controlled.

What standards prove air curtain performance?

The key aerodynamic test standards are ISO 27327-1:2009 and ANSI/AMCA Standard 220. They measure airflow rate, velocity projection, uniformity and power consumption under controlled laboratory conditions, allowing genuine like-for-like comparison.

What size air curtain do I need for my doorway?

Size to the door’s height and width, its exposure to wind and pressure, and the application. The nozzle should span the full width with no gaps, and the unit’s throw should comfortably exceed the door height. For tall or exposed doors, choose a centrifugal or high-velocity range. Thermoscreens can size the unit for you.

Electric or water-heated air curtain — which is better?

Electric units offer instant, responsive heat and simple installation where there is no wet system. Water-heated (LPHW) units are typically more energy-efficient for buildings with a boiler or heat-pump plant. The right choice depends on the available building services.

A high-performance air curtain is not the one with the biggest headline velocity figure — it is the one whose velocity, volume and uniformity are correctly balanced for your door, proven by independent testing, and controlled intelligently so it only works when it needs to. Get that right and you gain lower energy bills, a more comfortable entrance, cleaner indoor air, and an upgrade that typically pays for itself within two years.

Specifying an air curtain for a project? Talk to the Thermoscreens technical team for free, application-specific sizing and selection, or download the full product literature to compare certified performance data across the range.

➡️ Request a specification or sizing consultation ➡️ Download the Thermoscreens product brochure