The IECC and IgCC building codes list AMCA certified air curtains as viable alternatives to vestibules.

Learn more about Berner’s AMCA certified air curtains.

Published on the NEWS on September 8, 2014.

There has been a deluge of recent technological advancements that are creating new air curtain applications that were barely imaginable 10 years ago. Advancements range from more efficient electric heaters to manufacturing improvements that now extend lengths up to 16 feet. Air curtains that were once only custom-manufactured with explosion- and spark-proof components for hazardous industrial locations are now standardized catalog items. What was once an energy-saving device for industrial shipping doors is now embraced by retail, hotel, restaurant, and food service operators as tools for saving energy, eliminating flying insect infiltration, and increasing employee comfort.

Air curtains, also known as air doors, are typically mounted inside the top of a doorway and continually discharge a steady stream of air down the threshold to separate indoor and outdoor environments. The airstream keeps unwanted cold or hot air from infiltrating an open doorway during winter or summer, respectively. The units also keep out flying insects and maintain a comfortable working environment for employees.

Airstream Efficiency

Air curtains have offered electric heating coil options for decades; however, their traditional mounting in the airstream disrupts the laminar flow that’s critical to its efficacy. Such an obstructing placement can cut airstream efficiency by up to 40 percent. Furthermore, electric heater placements in the airstream disrupt the air curtain’s all-important volume, velocity, and uniformity (VVU), which is critical for maintaining an air seal across the entire doorway for ultimate efficacy.

In addition to the discharge air, electric heaters have also been mounted at the inlet screen where air is drawn into the air curtain. While this positioning doesn’t affect the discharge, it’s less energy-efficient because the air curtain enclosure itself becomes heated. This causes up to a 5 percent heat loss radiated through the cabinet that doesn’t reach the targeted area.

One recent invention that has corrected these inefficiencies is the Venturi-style heater, which is a hemispherical electric element array that’s strategically mounted at the air curtain blower’s inlets. Instead of an obstructive mounting in the discharge air, the element’s heat is drawn naturally into the blower via the Venturi effect, which is named for Italian 19th century physicist Giovanni Battista Venturi.

Essentially, the heating element is on the incoming side versus the discharge end of the fan/blower. The result of the Venturi effect heater is an electrically heated air curtain with no discharge obstruction; thus, the air curtain gets nearly 100 percent of the airstream’s aerodynamic potential.

Hazardous Locations

Petroleum refineries, food processing factories, pharmaceutical plants, chemical facilities, compressed natural gas (CNG) bus garages, and other hazardous locations (HL) are restricted by codes that allow only electrical components that are explosion-proof, spark-proof, and abide by other safeguards.

These special processes and environments typically create gases, dust, and other flammable or ignitable elements that can create fires or explosions generated from the spark of an electric motor, contact between ferrous metals, or arcing between electrical connections.

For years, custom-built HL-rated air curtains were available for this type of clientele, but they were custom-manufactured. Now, air curtain manufacturers are offering them as a standardized product line item, which lowers costs significantly and improves availability and lead times.

HL applications now offer large door coverage with explosion-proof motors ranging ½ to 15 hp and heavy-duty blowers to protect doorways up to 20 feet tall.

Extending Air Curtain Length

Another standardization of air curtain product lines is length. Previously, doorways wider than 12 feet typically had modular units bolted together or custom-made single-unit constructed air curtains, the latter of which carried expensive manufacturing costs. However, new technological manufacturing advancements make 16-foot lengths possible as standardized catalog items for some manufacturers. Industrial doorways commonly span widths of 12-16 feet.

The important aspect of single-unit construction is installation ease and performance. In comparison to multiple short units bolted together, single-construction air curtains typically don’t need intermediate supports, which can increase installation time and costs. Furthermore, the space between bolted units typically creates air voids. Single-construction units designed for 16-foot lengths use blower and nozzle airstream widths that cover the entire span without any interruption or turbulence. The VVU of the airstream, which can only be accomplished with a single-construction unit, is critical to air curtain performance and efficacy.

Air Curtains Substituting for Vestibules

Recent updates to the 2015 International Energy Conservation Code (IECC), which is published by the International Code Council (ICC), will now allow certified air curtains as a vestibule alternative. This is good news for commercial buildings that, in the past, were mandated to use vestibules as energy-saving airlocks.

This code change offers both a new construction and a retrofit perspective, especially for retailers. In retrofit examples, installing an air curtain and using the vestibule for merchandising space can add to a retailer’s bottom line.

The 2015 IECC code also stipulates air curtains must be tested in accordance with standard ANSI/AMCA-220 and certified by the Air Movement and Control Association Intl. Inc. (AMCA), a not-for-profit organization that tests and certifies manufacturers’ stated performance of fans, blowers, air curtains, and other air movement devices.

Food Service Applications

Walk-in cooler air curtains have been shown to surpass the energy-saving potential of alternatives, such as swinging hinged doors and strip curtains, and they produce a quick payback of less than two years, depending on the number of door cycles. While they are now predominantly appearing as options on new models from walk-in cooler manufacturers, several air curtain suppliers make retrofitting easy with a kit that includes an air curtain designed specifically for the unique size and configuration of walk-in coolers. Included in some kits are a prewired 24-V control/load center in a small enclosure and a magnetic reed on-off door switch. Once 120-V power is extended to the area, the prewired kit can be installed in as little as 15 minutes with conventional tools and basic electrical knowledge.

Besides walk-in coolers, another trend in the food service and restaurant industries is the use of drive-thru window air curtains, which are being used for a variety of purposes in many restaurant chains. They minimize both flying insect and outdoor air infiltration and protect the indoor drive-thru station employee from idling vehicle fume inhalation as well as cold air in winter climates, which are employee health and comfort issues, respectively. The U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA) specifically recommends a “reverse-flow fan system” at its “Teen Worker Safety in Restaurants” page.

As technological advancements move forward, even more new air curtain applications are expected to emerge. What is barely imaginable today may soon become common building construction concepts in the future.

CONFIRMATION

“If you ask most engineers or architects if air curtains are more energy efficient or less expensive than vestibules, they probably don’t know for sure, but this study reveals what we’ve known for some time,” said Timothy Londeree, R.A., architect, David A. Levy and Associates, Akron, Ohio, a retail design and development firm that has specified air curtains on dozens of commercial projects to save clients construction costs.

Berner executives said they hope the certified research will open a dialogue between the industry and the International Energy Conservation Code (IECC). Currently, the IECC doesn’t accept air curtains as viable alternatives in its Air Leakage – Section 802.3. Thus, the research study is another example of Berner providing customers with custom solutions to real market issues.

“Our clients want to save operating costs by using air curtains and eliminate the $20,000 to $60,000 cost of vestibules in their store designs, but they also want to stay within the IECC code,” said Berner project engineer Phil Thomas, who oversaw the project with engineering manager David Johnson.

THE STUDY ALSO CONFIRMED THAT BUILDING OWNERS SAVE MORE ENERGY, CONSTRUCTION COSTS, AND FLOOR SPACE.

AIR CURTAINS:

use less supplemental heat than vestibule heaters;
help enhance employee comfort;
reduce liability by maintaining drier entryway floors during inclement weather;
help keep traffic flow unhindered;
improves sanitation by reducing insect entry.

The culmination of energy and construction savings adds up to a one- to three-year payback for an air curtain, according to the study.

The Air Movement and Control Association (AMCA), Arlington Heights, Ill., a nonprofit organization that creates standards for, and tests/rates everything from air curtains to dampers, louvers, outside air grilles, fans, and other air-side HVAC equipment, hopes to change codes to address air curtains as a vestibule substitute. Armed with the research study, the association is currently lobbying code committees.

Architects, engineers, and specifiers can still comply with codes and use air curtains as vestibule substitutes, but it’s usually done at the local inspection level.

MORE ADVANTAGES

Another sometimes-overlooked advantage of air curtains is employee comfort. Because point-of-purchase (POP) stations typically are located near entryways for security reasons, POP employees don’t enjoy the same air comfort of their interior counterparts. Cashiers tend to get the brunt of unchecked wind in the absence of vestibules or air curtains.

In the case of vestibules, cold outdoor air can penetrate the entryway, especially when both sliding door entrances open simultaneously during heavy traffic periods. Supplemental space heaters, which can be costly to install and operate, temper the vestibule space air that infiltrates the POP area. Air curtains can be specified with built-in electric heaters or heating coils that are supplied by the building’s central heating supply loop to temper the air.

In the summer, hot, humid air infiltrates the space and makes work areas near doors uncomfortable for employees.

BEYOND VESTIBULES

Air curtains also have a variety of other applications. For example, the extension of the TD Banknorth Garden’s commuter foot traffic area 100 feet into the adjacent train shed of the Massachusetts Bay Transit Authority’s (MBTA’s) North Station was an energy-saving opportunity.

Architect Sasaki and Associates, Boston, and HVAC project engineer Jeff Fleishman, Cosentini Associates, Cambridge, Mass., were concerned with energy efficiency as much as aesthetics. Consequently, Sasaki’s idea of a 12-foot-high lobby/soffit design now presents an environment that’s comfortably separated from the outdoor air of the mammoth train shed via 12 air curtains at the mouth of 12 automatic sliding doors. During rush hour when the automatic doors are constantly open with passing commuters, the air curtains keep cold air from infiltrating the new train station lobby area at great savings to the building owner, Delaware North Companies Inc.

Summertime operation prevents hot, humid air from infiltrating the lobby space. Except for the gentler airstream at the entrance, commuters don’t notice the air curtains, which are flush-mounted above into the new lobby’s perimeter soffit.

Cosentini custom ordered factory-installed coil-filter combination options that all have hot water coils that tap into the soffit’s heating supply loop. The 95,600-Btuh coils supplement the new entrance area’s main HVAC system by providing thermostatically controlled heating near the door areas when needed.

Each air curtain also includes a control package, which includes a thermostat; three-speed fan with maintenance access from an onboard control panel; a timer delay function; and a low-voltage relay for tapping into direct digital control (DDC) building automation systems.

MCCORMICK PLACE

Another innovative use of air curtains is Chicago’s new McCormick Place West convention center. When officials of the Metropolitan Pier and Exposition Authority (MPEA), which owns and operates the facility, were presented with energy conservation estimates of $70,000 annually and equipment cost paybacks of less than two years, choosing air curtains looked like a good thing.

Air curtains were one of several energy-conserving technologies that helped the project achieve two of its Leadership in Energy and Environmental Design (LEED) points from the U.S. Green Building Council (USGBC) in the Optimized Energy Performance category.

The $850 million exposition facility has more than 375 linear feet of freight and pedestrian doors, which are typically open 10 to 14 hours daily during the five-seven days of setup prior to major winter events. Many air curtain manufacturers can perform an energy savings estimate for customers by gathering and calculating dozens of site conditions data. Some of McCormick Place West’s data calculations considered a 26-week heating season, with each door open 10 hours weekly for a total of 260 hours annually. Besides the annual savings and payback, there was also a calculated hourly savings of $269.79 when all the doors are open simultaneously.

Air curtains also have an impact on indoor air comfort in the facility’s 470,000 square feet of open exhibition space. Without the air curtains on all large roll-up doors and main doors, temperatures would drop dramatically during set-up and tear-down, and it would require a minimum of 24 to 48 hours to regain the target temperature of 73° to 75°F for an event, according to Susan Van Klompenburg, senior mechanical design engineer, A. Epstein and Sons International Inc., which performed consulting engineering for the McCormick Place West expansion as a member of the joint venture, McCormick Place Design Team, Take II LLC, Chicago.

Furthermore, employee air comfort can affect productivity significantly. Shows are set up more efficiently in cold, wintertime months at McCormick Place West because employees are more comfortable. Moreover, forklifts can pass freely through freight doors without waiting for them to cycle.

IN THE STUDY

Thomas and Johnson recorded and compiled hundreds of statistics based on the geometry and scale of conventional vestibule architecture used by three national pharmacy chains. Three building configurations (vestibule only, air curtain only, and vestibule and air curtain) were simulated with wintertime ambient temperatures of 20°F under a variety of wind loads and traffic frequencies. The dozen scenarios were 3-D modeled in SolidWorks 2007 and launched into CFdesign upfront CFD software by Blue Ridge Numerics.

CFdesign was chosen because of its ability to model moving solids in numerous scenarios and to allow recorded measurements in a multitude of scalar and vector quantities in a precise and repeatable manner. Similar test results would have been impossible with other testing methodology such as simple mathematical equations.

“Physical lab testing procedures might have given a similar result, but CFD analysis cut test time by as much as 60 percent, not to mention the additional production costs of building a vestibule test site,” said Jason Pfeiffer, director of engineering services, Blue Ridge Numerics, which is a world leader in upfront CFD and engineering services.

For more information, visit www.berner.com.

Sidebar: Air Curtains and LEED Credits

Berner air curtains, which have been certified by the Air Movement and Control Association (AMCA), can help to achieve Leadership in Energy and Environmental Design (LEED) Energy and Atmosphere points, as well as Indoor Air Quality points. Here are a few of the main areas in which the proper use of an air curtain can help a building achieve LEED points.

Energy and Atmosphere Points (EA Credits 1)

Credit EA 1 – While air curtains are not a major part of an HVAC system, used properly, air curtains can increase a space’s energy efficiency when the doors are opened – decreasing energy consumption and increasing occupants’ comfort. For this credit (good for up to 10 points), the LEED certification process requires a whole building project simulation that shows the percentage improvement in the proposed building performance rating compared to the baseline building performance rating per ASHRAE/IESNA Standard 90.1-2004.

Indoor Air Quality Points (EQ Credits 6.2 and 7.1)

Credit EQ 6.2 – Air curtains provide a high level of thermal comfort system control by individual occupants or by specific groups in spaces that are surrounding openings (i.e., loading dock doors, customer entryways) to promote the productivity, comfort and well being of building occupants (Thermal Comfort: Controllability of Systems, Credit 6.2).

Credit EQ 7.1 – By preventing thermal drops or rises due to a system’s reaction to cross-contamination of airstreams near an open doorway, air curtains can help an HVAC system comply with ASHRAE Standard 55-2004, Thermal Comfort Conditions for Human Occupancy. For example, cold winter air near the door may kick the heat on, causing spaces away from the door to be overheated (Thermal Comfort: Compliance, Credit 7.1).

Innovation in Design Points (ID Credits):

Credit ID 1-1.4 (good for 1 point) – Because doors are already closed when a building is commissioned, air curtains are not always included in the mechanical testing process. However, when used properly, air curtains help to increase energy performance (decrease energy use), and it is common to see a payback period of one-two years depending on location and use. It has been recommended that if the benefits of air curtains are not being captured elsewhere by the LEED-NC Green Building Rating System, air curtains should be submitted for this credit.

Some air curtains can also be used for insect control. If a client is putting together a Low Environmental Impact Pest Management Policy to minimize the use and cost of chemicals, air curtains can help achieve Indoor Environmental Quality points in the LEED for Existing Buildings Rating System.

Indoor Environmental Quality Points (EQ Credits 10.4 and 10.5)

Credit IEQ 10.4 and 10.5 – Low Environmental Impact Pest Management Policy.

For more information, visit www.usgbc.org.

Published by AMCA International – October 2013

Air curtains can be considered as an alternative to vestibules in accordance with IECC-2015.

ARLINGTON HEIGHTS, IL., October 30, 2013 – Air Movement and Control Association International, Inc. (AMCA International) announced today that the 2015 version of the International Energy Conservation Code will contain a provision enabling air curtains to be considered as an alternative to vestibules. For compliance, air curtains have to be tested in accordance with ANSI/AMCA Standard 220 and be installed in accordance with manufacturer’s instructions.

The International Energy Conservation Code is published by the International Code Council, “a member-focused association dedicated to developing model codes and standards used in the design, build and compliance process to construct safe, sustainable, affordable and resilient structures.”

Air curtains are devices installed above exterior door thresholds that blow a film (curtain) of air downward when the door is opened, trapping conditioned air inside the building.

“The IECC provision complements a similar provision adopted by the 2012 International Green Construction Code. Taken together, air curtains can help meet baseline energy codes and green construction codes,” said Brian Jones, Engineering Manager, Powered Aire, Inc., Greenville Penn., and chair of the AMCA Air Curtain Engineering Committee.

“AMCA International is proud of the AMCA Air Curtain Engineering Committee, Air Movement Code Action Review Committee, and Intercode Incorporated for their combined efforts to develop and support this successful code change proposal. We also want to thank the Colorado Chapter of ICC for working with us to develop the language, as well as the numerous code officials from around the country who supported and voted to approve the code change proposals,” said Wade Smith, PE, Executive Director, AMCA International.

In a competitive auto retailing economy, car dealerships always look for a competitive edge. Mel Grata Chevrolet/Toyota has found climate-controlled indoor air comfort greatly improves customer satisfaction especially during cold Pennsylvania winters.

Mel Grata Chevrolet/Toyota’s new green service bay buildings in Hermitage, Pa., save energy while keeping employees and customers warm.
In a competitive auto retailing economy, car dealerships are always looking for an edge, and Mel Grata Chevrolet/Toyota has found that climate-controlled indoor air comfort greatly improves customer satisfaction, especially during cold Pennsylvania winters.
Instead of fighting inclement weather, Mel Grata customers now drive through one of two new climate-controlled service/staging areas featuring doorway air curtains. The air curtains, also referred to as “air doors,” efficiently separate the indoor and outdoor environments and maintain indoor temperatures, even with constant door openings during morning rush hours.
The Chevrolet service area was expanded into a 2,000-square-foot, newly remodeled three-bay space. The separate 1,500-square-foot Toyota service area is a recently built two-bay, four-door space. Both buildings adjoin the dealership’s main 75,000-square-foot showroom and office complex. Industrial Direct Drive 12 Series air curtains with three-speed motors, manufactured by Berner International, New Castle, Pa., seal each of the seven 12 x 12-foot doorways with a controlled airstream to protect against outdoor air infiltration during hundreds of daily door cycles.
“Without the air curtains, it would take several minutes for the heating system to recover our 70°F set point temperature that keeps customers and employees comfortable,” said President Mel Grata, who conceived of the idea after seeing air curtains in action on truck docks, vestibules and retail store entrances.

“We’ve had no air comfort complaints from customers or employees even on the coldest winter days, and that’s good for business,” said Grata.
— Mel Grata, President, Mel Grata Chevrolet/Toyota

Find out more about Berner’s line of Industrial air curtains.

Good news for building owners, engineers/architects, and HVAC contractors who can now save energy, construction costs, and space in commercial facilities with this latest approved code addition.

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