ASHRAE Journal - May 2022 - 27

COLUMN ENGINEER'S NOTEBOOK
PHOTO 1 Sidewalk elevator.
The third exception is also common.
It states that you do not need
hoistway venting if your elevator
serves an open parking garage only.
The elevator cannot also serve an
attached building.
The fi nal exception states that you
don't need hoistway venting for an
elevator in an individual residence.
Refer to Figure 1 for a hoistway venting
fl ow chart.
If your elevator penetrates four
stories or more and you don't meet
any of the exceptions, you need to
have hoistway venting. The code
specifi es how this must be done:
Vent Location. The vent must
fi fth fl oor is not serving two fl oors.
It is serving fi ve fl oors. If the elevator
serves three fl oors or less, you
do not need hoistway venting. If
the elevator serves more than three
fl oors, you might need hoistway
venting. I say " might " because there
are four exceptions to this code
requirement.
The fi rst exception is the most
common. It states that unless you
are Group R-1, R-2, I-1 or I-2 occupancy
or similar occupancies with
overnight sleeping rooms, you do
not need hoistway venting if your
building is equipped throughout
with an automatic sprinkler system.
The exception excludes Groups R-1,
R-2, I-1 or I-2 and similar occupancies
because these occupancies all
have overnight sleeping rooms and
the code holds them to a higher life
safety standard. (The IBC defi nes
Group R as Residential and Group I
as Institutional.)
The second exception states that
hoistway venting is not required for
sidewalk elevator hoistways (Photo 1).
These are not often seen in our
industry.
be located at the top of the hoistway
and open to the outside or be
ducted to the outside through a
non-combustible duct enclosed in
fi re-rated construction equivalent
to that required for the hoistway,
typically two-hour rated. If the
machine room is at the top of the
shaft, the vent will duct through
the room and out the top of the
machine room roof. If the elevator
shaft extends above the roof, the
code offi cial may allow the vent to
be on the side of the shaft above the
roof rather than at the top. You must
verify with the local code authority
whether they will allow this location
because " top " of hoistway is subject
to interpretation.
Vent Size. The vent must have an
area that is equal to or greater than
3.5% of the hoistway area (plan footprint)
or 3 ft2 (0.3 m2) per elevator
car, whichever is greater. The code
does not say the opening has to be
square or give a minimum dimension
in any direction. Typically, vents
are square or rectangular because
this results in lower cost and easier
installation. It also states that at least
1/3 of the area must be permanently
open. The entire vent could be
permanently open, but that allows
more unconditioned outdoor air
into the shaft, which can potentially
affect space comfort, raise energy
consumption and potentially freeze
sprinkler pipes in the hoistway. The
portion that is not permanently
open must have annealed glass not
greater than 1/8 in. (3.2 mm) in
thickness. This is uncommon and
not done much anymore. Photo 2
shows the glass option.
There is an exception in the code
to this requirement:
" Exception: The total required vent
area shall not be required to be permanently
open where all the vent
openings automatically open upon
detection of smoke in the elevator
lobbies or hoistway, upon power
failure and upon activation of a
manual override control. The manual
override control shall be capable
of opening and closing the vents
and shall be located in an approved
location. "
This exception allows you to use
a motorized damper. The manual
override control is typically at the
fi re command center. Most designs
are either permanently open for
the entire vent area, or the entire
vent area has an automatic motorized
damper. A common approach
to designing the vent is to locate
it at the top of the hoistway roof
(or ducted up to the roof) with an
automatic motorized damper and
a louvered penthouse. It could
also be an opening with a louvered
penthouse (no damper), but as
mentioned previously, this can
waste energy.
A lesser-known part of the code
regarding hoistway venting is the
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ASHRAE Journal - May 2022

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