ASHRAE Journal - ACMA Supplement - Fall 2013 - 22

By david a. Johnson, Director of
engineering, Berner international corp.,
new castle, penn., fRank R. cuadeRno,
Vice presiDent of engineering, Mars
air systeMs, llc, garDena, calif., anD

How
air curtains Work

BRian Jones, engineering Manager,
powereD aire, inc., greenVille, penn.

recent study comparing the energy
performance of air curtains to vestibules
determined that in many climate zones, air

curtains save energy and operating costs. this article
describes the study and its results, and reviews how
air curtains work and their many benefits.

An air curtain installed on the interior of a building provides a
coherent sheet of air created by the discharge air stream and the
surrounding entrained air. This sheet of air is able to bend and
resist thermal exchange over an opening in the building envelope
by using the building’s interior pressure. Stability is created
when the air stream meets a return grill or splits when it meets
a surface, such as a floor or another air stream.
Air curtains are not intended to replace physical doors, but they
can be used as a low-cost, low-maintenance alternative to a vestibule. Air curtains can free up valuable floor space and create an
invisible, energy-saving barrier that reduces infiltration when the
door is open. Efficiency (or effectiveness) is determined by only
considering the operating cost when the door is open. Some air
curtains include heating options to conveniently warm interior
spaces, but only ambient air is needed to provide the most important
feature of an air curtain—separation between spaces. The most
common types of controls are switches triggered by the door, or
motion sensors that are triggered by people approaching the door.

Rating and ceRtification

Air curtains are rated in accordance with ANSI/AMCA 220,
Laboratory Methods of Testing Air Curtain Units for Aerodynamic
Performance Rating. AMCA 220 defines specific test procedures
that are administered by accredited manufacturers or third-party
laboratories. The critical rating parameters determined by AMCA
220 are core velocity projection, power rating, uniformity, and
air volume.
AMCA’s Certified Ratings Program provides a quality assurance measure that ensures publicized air curtain ratings are
accurate. AMCA’s certified ratings database at www.amca.org
is updated in real time with new and updated air curtain ratings.
If a claimed certified rating is not in or is different from that
in AMCA CRP database, it cannot be trusted.
aiR cuRtains in eneRgy and gReen constRuction
codes

Air curtains are approved as an alternative to vestibules in the 2012
International Green Construction Code. To meet the code provisions,
air curtains must be tested in accordance with AMCA 220.
new eneRgy study foR aiR cuRtains

The most recent air curtain study, Investigation of the Impact of
Building Entrance Air Curtain on Whole Building Energy Use1,
was conducted by Liangzhu Wang, PhD, assistant professor at
the Department of Building, Civil and Environmental

Figure 1: Infiltration/exfiltration characteristics of an air curtain jet under different pressure differences,
ΔP = Po – Pi . (Note the zero infiltration does not apply to the air recirculating through the air curtain.)
Image courtesy of AMCA International

OUTDOOR

(a). Zero infiltration
when ∆Plc < ∆P < ∆Puc

Fa l l 2 0 1 3

INDOOR

OUTDOOR

INDOOR

(c). Exfiltration
when ∆P > ∆Plc

(b). Infiltration
when ∆P > ∆Puc
a m c a I n t e r nat I o na l

OUTDOOR

inmotion

w w w. a m c a . o r g

http://www.amca.org http://WWW.AMCA.ORG

ASHRAE Journal - ACMA Supplement - Fall 2013

Table of Contents for the Digital Edition of ASHRAE Journal - ACMA Supplement - Fall 2013