Air curtains that keep the cold in while the door stays open.

It blows a controlled sheet of air across a doorway so the air on each side stays where it is. At a cool room door that means less cold air pouring out at the bottom and less warm air rolling in at the top while the door is open. At a store entrance it holds the conditioned air in, and in a food area a unit built for it also makes the opening harder for flying insects and airborne dirt to cross.

A correctly sized and correctly set up curtain cuts the air exchange through an open door, and less exchange is less load on the refrigeration or the air conditioning. How much depends on the opening, how often it is open and how the unit is set, which is why the saving has to be measured at your door rather than taken off a brochure. Published research on a cold store door found the same unit going from 0.31 to 0.77 effectiveness on setup alone. Worked through for one Melbourne cool room door standing open four hours a day, the calculation on this page puts the net saving at about 1,160 kWh a year as typically installed and about 3,050 kWh set up properly, against 117 kWh for the curtain's own fans.

On the worked example on this page, one Melbourne cool room door open four hours a day, about 0.9 tonnes a year as typically installed and 2.4 tonnes set up properly, at the Australian Government's 2025 factor for Victoria. It is a calculation from a published doorway method with every input shown, not a measurement, and the biggest lever in it is the setup, not the unit.

Not on its own. NCC 2022 clause J5D5 names an airlock, a self closing door, a rapid roller door, a revolving door or the like for an entrance leading to a conditioned space, and an air curtain is not in that list. It can form part of a performance solution, which the building certifier assesses, and it is often worth fitting purely for comfort and running cost. Anyone who tells you it ticks J5D5 by itself should be asked to point at the clause.

Only if the unit was built for it. NSF/ANSI 37, the standard written for air curtains at food premises openings, sets a jet speed of about 8.13 m/s at a service door and 3.05 m/s at a customer entrance. A comfort unit chosen for an entrance draught runs well under that, so it will not do the insect job. If the brief came out of a food safety audit or a pest report, say so, because it changes the family of unit.

No. A curtain reduces the exchange while the door is open. It cannot hold a room at temperature when nobody is using the door, and it does nothing at all with the power off. The usual answer at a busy cool room is both: the door for the quiet hours, the curtain for the hours it stands open.

There are families built for sub zero openings, often two units with opposed jets, but it is a different specification and a harder one. Below zero the moisture in the incoming air turns to frost and then ice, on the grille, on the floor and in the door track, so where that moisture goes has to be designed rather than discovered. A unit rated for chambers above zero fitted to a freezer opening is the most common wrong purchase in this category.

It depends on the family. Commercial entrance and cool room units are commonly rated to project about three metres, and industrial families go to about seven metres. The rating matters more than the look of the unit: mounted above its rated projection, the jet arrives at the floor too slow to hold anything, and the curtain becomes an expensive draught.

Length to the clear opening width first, so the jet covers the whole gap, using units in line where one will not reach. Then the family and the speed to the mounting height and the temperature difference, then the control to how the door is actually used. We take air velocity and temperature readings at the opening before specifying, because door traffic, exhaust fans and the store air conditioning all change the answer.

Unheated is right for most Australian retail entrances, where the store is air conditioned and the job is holding the boundary. Heating earns its place where a cold climate entrance draught is a genuine comfort complaint, and it can be electric or run off an existing heating water circuit. Electric heating is the load to watch: it often needs three phase and spare capacity at the board, which makes it a switchboard question before it is an air curtain question.

Manufacturers publish a noise rating, commonly in dB(A) at five metres, and a unit usually has a quiet setting and a high one. It matters most over a service counter or near a checkout, because a unit that is too loud for the people standing under it gets switched off, and a switched off curtain saves nothing. The rating and the listening distance both belong in the specification.

An unheated commercial unit is typically single phase with a modest fan load, often well under a kilowatt for a domestic sized opening. Electrically heated and industrial units are a different matter and commonly need three phase and their own circuit. Breaker size and cable run are checked at the survey, so the electrical work is quoted with the unit instead of stopping the install.

On a door contact wherever the door is genuinely closed between uses, which is most cool room doors. Continuous running suits an opening that stands open all trading day. Wiring a continuous run to a door that opens thirty times a day is a running cost with no benefit, and it is one of the first things we change on curtains that were already there. In the worked example on this page, running the fans around the clock instead of on the door costs 584 kWh a year more, which is half the net saving of a curtain left at its installed settings.

Keep the inlet grille and any filter clean, because a blocked inlet costs jet speed straight away and cool room installs in humid areas clog faster. Beyond that it is fan bearings, and a speed check any time something changes at the door: a new door leaf, a new exhaust fan, a shopfit that moves the bulkhead. Ours get remeasured rather than assumed.

Because the number that matters is the one at your door. A data sheet describes a test opening in a laboratory, not a store entrance with a kitchen exhaust forty metres away and a cool room door that stands open through the morning pick. We read air velocity and temperature at the opening in each state before anything is ordered, and again after commissioning, so the business case is built on your readings.

Vertical units mounted at the jamb blow across the opening instead of down, and recessed units sit in the ceiling void with only the grille showing. Both are normal answers to a glazed shopfront with nowhere to hang a surface box. The trade off is planning: a recessed unit has to be coordinated with the ceiling, and with how the grille will be cleaned.

A strip curtain is plastic hanging in the opening: cheap, passive, and still working with the power off, but it clouds and tears, catches trolleys and stock, and staff stop trusting what is behind it. An air curtain leaves the opening clear, and needs power and setup to do anything at all. Do not fit both in the same traffic path, because strips hanging in front of a curtain break the jet up before it gets going.

Yes, and that is the normal shape of this work. A sample of stores is measured, one specification is set per door type, each store is priced, and the rollout stages against the capital cycle under one accountable team, with readings and photos filed per store.