Air Curtain Buyers' Guide
Doors and windows are both necessary and a frequent source of difficulties for businesses. Temperature fluctuations, flying pests, and consumer and employee discomfort are all cause for concern in most commercial and industrial buildings. When a window or door is opened, whether for seconds or hours, there is the opportunity for insects and unconditioned air to enter the building, which can cause problems and cost operators money. An air door creates an invisible barrier that can be used to protect your business from outside elements, or to separate areas inside.
What is an Air Curtain?
An air curtain, also known as an air door, takes in air from the front of the unit and expels it at high velocity across the door or window opening. That sheet of high-speed air can block intrusion by flying insects, dust and debris, hot and cold temperatures, and even wind. Air doors are available in a wide range of sizes and with motors ranging from 1⁄6 to 7 HP, so there are air curtains available for openings as small as drive-through windows and as large as warehouse docking bay doors.
Air curtains save operators money on both HVAC energy costs and pest control. A properly sized and calibrated air curtain will retain 75 to 80 percent of the indoor air, reducing the work that the building's HVAC system must do to maintain the set internal temperature and eliminating the need to keep a solid door closed at all times. Air doors are recommended by the U.S. Green Building Council as a way to help manage energy usage while maintaining comfort, and can contribute toward earning LEED points. For example, the sprawling McCormick Place convention center in Chicago saves as much as $269.79 per hour when all the doors are open with air curtains in place to help maintain temperature.
In addition to energy savings, an air curtain can provide chemical-free, preemptive flying pest control that can save your business money in the long run and improve customer perception and food safety in restaurants. This is especially important on back doors located near dumpsters that attract flying insects.
Air Curtain Applications
The most important thing to know when shopping for an air curtain is the width and height of the opening you will install it on. An air door should always be at least as wide as the opening, and the velocity of the air flow will need to increase as the height of the door does. Below are some of the most common air door applications and the options available for those uses.
Used in: Fast food, pharmacies, concessions, food trucks
Drive-through and other serving windows are frequently opened, placing them among the most important places to install air curtains, which, beyond the benefits already noted, can keep out vehicle exhaust in these applications. Models designed for such use are available in stainless and powder-coated steel, and can be set to turn on automatically when the window opens or to be turned on manually. Heated models feature an on/off switch for the heat. Drive-through air curtains have an extra focus on keeping noise low to enable servers to hear orders.
Front and Back Doors
Used in: Restaurants, convenience stores, supermarkets, retail, offices, hotels, healthcare, schools
Front and back doors are important places to protect, and an air door can form a barrier that activates automatically when the door is open or can be activated manually as needed. Front doors most often need an air door for environmental control, as this is where customers enter; an air door with a heated option may be needed in the winter in some climates. The focus of most back door air curtains is preventing the ingress of flying insects, as those entrances are often near dumpsters that attract these pests. Additionally, those doors are more likely to be held or propped open for longer periods as items are brought into and taken out of facilities. Because of this, models made especially for back doors typically have motors offering higher horsepower capacities and may not have the attractive finishes as those designed for use in customer areas.
Used in: Restaurants, manufacturing, distribution
Air curtains are made to form a barrier, which can certainly be useful in more places than exterior doors. These can be used in restaurants as barriers between kitchens and dining areas as a way of containing excess heat to the kitchen. Air curtains are also commonly used in manufacturing facilities to separate stages of manufacturing, preventing the spread of paint, fumes, or wood or plastic particles. For large manufacturing areas, you may need a more powerful air curtain if it will be mounted high over the floor.
Commercial Bay Doors
Used in: Manufacturing, distribution, automotive shops, street-facing restaurants, retail
Any business that deals with incoming deliveries and outgoing shipments is likely to have a commercial bay door on the loading dock. These doors might be open for hours at a time as your building's conditioned or heated air escapes and your utility costs push steadily upward. Air doors are available that put out an air stream at a strong enough velocity to cover a door opening as high as 30 feet. These can also be used in street-facing bars or restaurants that leave their doors open to patios but still want to air condition the inside.
Used in: Restaurants, supermarkets, convenience stores
An air door placed in a walk-in cooler can help retain the cool temperatures inside when the door is opened. This helps keep food safe by keeping temperatures steady and makes your cooler more energy efficient. While most air curtains can function in a cooler, if you plan on using the curtain in a freezer, you may need to buy a specialty model that can work in the freezing temperatures without damaging the internal parts.
Switch and Control Options
Because air curtains are generally mounted over a door where it's hard to reach, it's important to have the right activation devices. The controlling device you need will depend on the type of air curtain you have and the features it includes.
Wall switches allow users to handle the settings on the air curtains from control panels mounted on walls near the equipment. The simplest of these controls is an on/off switch, which is usually a basic toggle switch, but most models can at least make use of a variable speed switch, which is usually offered as an additional option. A variable speed switch can be a toggle or knob switch with high/low/off options or a knob-style switch with variable speeds. Heated air curtain models included controls to toggle heat on and off. Individual wall-mounted switches are available to control the heat function, and some control panels include switches to control both fan speed and heat. These wall-mounted control panels are most often used in warehouse interiors and shipping area bay doors where the air doors will be running for extended periods of time.
For front and back doors, drive-through windows, and walk-in coolers, it usually makes more sense to have a switch that turns the unit on automatically when the door or window is opened.
- A magnetic door switch can use solar or battery power, or a combination of the two. These use a set of magnets positioned on the door and door frame that will trigger the air door to come on when the magnets are separated. When the door closes and the magnets are aligned again, the air curtain will turn off. This type of switch is compatible with most doors and drive-through windows.
- Another option is a motion sensor, which turns the air curtain on as movement is detected near the door. These are compatible with most door types, but should not be used in areas where there is a lot of movement, such as drive-through windows. These require a power source and are usually hardwired.
- The most common door switch type is the plunger/roller door switch due to it also being the most versatile; it can be used in almost any application. These use the pressure applied by the door to a plunger to determine whether the door is open or closed, which in turn activates the air door when needed. This type of switch is usually installed by an electrician so it can be hardwired for electricity.
If your air curtain is heated, you will likely need a heat switch control panel mounted nearby in addition to the door switch you choose.
Selecting an Air Door
The most important factor in choosing an air door is the size of the opening you’re outfitting. The width of the door or window is the basis for determining the width of the unit, while the height of the opening will dictate the air force needed to be effective all the way to the ground. Each air door model has a recommended maximum mounting height to ensure the unit can work as high as you need. These heights start as low as 5 feet for drive-through windows and go all the way to 30 feet for the largest openings in shipping and receiving docks. Air curtains are available in widths as long as 192 inches, but in most locations tandem mounting is an option to cover wider openings.
A few other factors to keep in mind while selecting a commercial air curtain include:
- Building air pressure: In some cases, especially in kitchens, negative pressure can make an air door less effective. This may be circumvented in some cases with a unit with a higher-horsepower motor, but usually the building's makeup air system will need to be adjusted to even out the pressure balance between the building and the outdoors for the air door to function properly.
- Heated air doors: If your region experiences cold winters, a heated air door can help maintain the temperature of your climate-controlled areas. Electric heat is the most common option, but operators with proper access to the utility may choose a model that makes use of steam or gas. These will require a more expensive installation, but in some areas can save you money on utilities over time.
- Mounting options: Air curtains can usually be mounted directly to a wall, but in some locations wall mounting brackets or a mounting plate may be needed. That condition is most common in facilities that use roll-up doors that need to be worked around. Some air door models can also be recessed into a drop ceiling for a more streamlined look, and some can be mounted vertically along one side of the door where the ceiling is too low to allow for a traditional installation.