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Engineering of Concordia University, Montreal, Canada. Dr.
Wang compared the energy performance of an air curtain mounted
over a single-entry door versus a vestibule using an integration
of three types of modeling software.
Using ANSYS Fluent CFD software, Dr. Wang found that an
air curtain reduced air infiltration significantly across a building
entrance door under various pressure conditions. The entire
building annual energy usage then was determined using TRNSYS energy modeling software and CONTAM software for
modeling building air pressure and infiltration. The results verified that the air curtain allowed less infiltration than a vestibule
for a given building. The study found that in all of the climate
zones where the IECC currently requires vestibules, an air curtain
was equally effective or better at energy savings.
To model the air curtain in a whole-building simulation, two
steps were necessary: First, three door setups were used to
determine the amount of air infiltration through the building
1. Single door without a vestibule or air curtain (hereafter, a
2. Single door equipped with an air curtain (hereafter, an air
3. A vestibule with two sets of doors (hereafter, a vestibule
1,146 kWh – 18,986 kWh in energy savings, with greater performance achieved in colder climate zones.
The study illustrated that heating efficiency accounted for the
air curtain door’s major savings. Because no changes were made
to the operating characteristics of the air curtain, total savings
in Zones 1 and 2 were marginal, or 0.0% – 0.1% (81 kWh ~ 132
kWh) when compared to the single door.
The study also found that building entrance orientation, building
pressure, and frequency of door usage all affect air infiltration/
exfiltration, and the resultant energy performance of the air
curtain door. In particular, the effects of building entrance orientation and the balance of the HVAC system were shown to be
as important as the frequency of door usage.
Dr. Wang’s final report can be downloaded at no charge at: www.
Second, research determined the impact of air infiltrations on
the whole building and annual energy use for the three different
Infiltration through the single door and vestibule door setups
was calculated by a commonly used orifice equation model,
which considers the amount of infiltration to depend linearly
on a power law function of the pressure difference across the
door. Yuill (1996)2 conducted extensive experimental studies
to provide the orifice equation models for both single and
vestibule doors based on door usage frequency, geometry, and
pressure difference across a door. The infiltration model for
the air curtain door was determined using the method similar
to that in Yuill’s study, in conjunction with the multi-model
CFD program described above.
For the modeled DOE3 medium office building, the major conclusions demonstrated the annual energy use of the whole building
with the air curtain installed is less in all of the climate zones.
Energy use is less than the single door in Climate Zones 1 – 2,
and less than the vestibule door in Climate Zones 3 – 8.
Additionally, the modeled air curtain door reduces air infiltration
significantly under the same conditions when compared to either
the single door or the vestibule door.
The modeled air curtain door also provided comparable performance to the modeled vestibule door for climate Zones 3–8.
Compared to the vestibule door, the air curtain door can reduce
energy use by 0.3% to 2.2% for Zones 3 – 8, corresponding to
w w w. a m c a . o r g
a m c a I n t e r nat I o na l
Wang, L. 2013. “Investigation of the Impact of Building
Entrance Air Curtain on Whole Building Energy Use.” http://
Yuill, G. K. 1996. “Impact of High Use Automatic Doors
on Infiltration.” ASHRAE RP-763.
Cho, H., K. Gowri, and B. Liu. 2010. “Energy saving impact
of ASHRAE 90.1 vestibule requirements: modeling of air
infiltration through door openings.” Oak Ridge, Tenn.,
Pacific Northwest National Laboratory: 47.
Benefits of air curtains
Approved as an alternative to vestibules in the 2012 IgCC,
air curtains make egress in an emergency exit situation
safer and faster by providing clear, uninhibited flow to the
traffic passing through it, while still saving energy during
heating and cooling seasons. Alternatively, with vestibules,
building occupants would need to pass through two sets of
doors instead of one.
An additional benefit of using an air curtain is a cleaner
indoor air environment. Air curtains can reduce the infiltration of dirt, fumes, and debris, and repel flying insects. As
recognized by ANSI/NSF Standard 37: Air Curtains for
Entranceways in Food and Food Service Establishments,
they are approved for the food service industry to control
insects at customer entry doors, service windows, and
Numerous studies have evaluated the effectiveness of air
curtains in terms of providing a separation between spaces.
Air curtains consistently meet the performance of or outperform vestibules in energy savings. Recent studies take
advantage of modern technology to evaluate air curtains’
efficiency and effectiveness, while considering installation,
operating costs, and maintenance costs.
ASHRAE Journal - ACMA Supplement - Fall 2013
Table of Contents for the Digital Edition of ASHRAE Journal - ACMA Supplement - Fall 2013
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