The addition of air curtains in the International Green Construction Code (IgCC), the new comprehensive high performance green building code slated for publication this month, aims for energy and construction cost savings for commercial, industrial, and institutional buildings.
An air curtain (also an “air door”), employs a controlled stream of air aimed across an opening to create an air seal. This seal separates different environments, while allowing a smooth, unhindered flow of traffic and unobstructed vision through the opening. Because air doors help to contain heated or air conditioned air, they provide energy savings and personal comfort when applied in industrial or commercial settings. Air doors can also be used to stop the infiltration of flying insects.
Specifying air curtains as energy saving, cost saving alternatives to vestibules in buildings that are 3,000 square foot and larger has been a recent trend among consulting engineers and architects. However, many times specifications are blocked by local jurisdictions that have adopted the International Energy Construction Code (IECC), which doesn’t yet recognize air curtains as vestibule alternatives.
Thus, the newly enacted IgCC provides an approved overlay of green construction products to the base code IECC, which is overseen by the International Code Council (ICC).
“Building owners have lobbied code organizations for an alternative to vestibules, because of their higher costs, waste of space, and less effectiveness compared to air curtains,” says David Johnson, director of engineering at air curtain manufacturer, Berner International of New Castle, PA. “The overlay helps high performance green building advocates push through design criteria such as substituting a vestibule with an air curtain, however it’s still up to the discretion of local code jurisdictions whether it’s accepted in a project.”
Recent proposals to the IgCC by the Air Movement and Control Association International (AMCA) of Arlington Heights, IL, helped establish air curtains as a vestibule alternative with the stipulation that they’re tested in accordance with ANSI/AMCA Standard 220-05, “Laboratory Methods of Testing Air Curtains for Aerodynamics Performance Ratings.”
Also helpful in the code modification effort were recent studies proving air curtains as 10% more energy-efficient than vestibules. The three month research study, “Air Curtains: A Proven Alternative to Vestibule Design,” used second-party validation from research/validation consultant, Blue Ridge Numerics of Charlottesville, VA (which has since been acquired by AutoDesk) with certified results from proven computational fluid dynamics (CFD) analysis.
Besides energy savings, Johnson also said vestibules, especially in retail settings, consume anywhere from 25 to 250 square feet of usable retail space and carry construction costs ranging from $3,750 to $37,500, based on an average of $150/square feet construction costs.
“The IgCC is an overlay code to the base energy code,” says Amanda Hickman, manager of regulatory affairs, Intercode Inc. of Delray Beach, FL, who along with Johnson, helped AMCA present data to IgCC committees. “This means the requirements of the IECC must be met first. The IECC does not contain the same allowance that the IgCC just accepted for an air curtain alternative.”
Meanwhile air curtain proponents will continue to present energy efficiency data to code committees, in hopes of instituting the vestibule alternative measure into the IECC. The next meeting on the subject is scheduled in January 2013.
“The next step for the air curtain industry is to seek the same allowance that was approved by the IgCC and get it into the IECC. Then, designers will be able to use an air curtain as an alternative to a vestibule full-stop throughout the country,” says Hickman.