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INDUSTRY NEWS
Greenbuild, From Page 6
2015 to Oct. 31, 2016, allowing projects to continue
to register under the less
stringent LEED 2009 during this time. The USGBC
cited a survey conducted
at this year’s Greenbuild in
which 61% of respondents
said they needed more
time to prepare for LEED
v4. Projects can continue
to be registered under the
more rigorous LEED v4,
but fewer than 400 projects have been registered
under LEED v4 since it was
introduced.
“LEED v4 created a
certain amount of chaos
with transparency and
disclosure,” said Dwayne
Fuhlhage, who attended
an educational session
related to evaluating the
risk of chemicals in building products. Fuhlhage
is Sustainability and
Environment Director
for PROSOCO, a building
product manufacturer
based in Lawrence, Kan.
“It’s not all been resolved.
We’re seeing a gradual
maturing.”
“It is triggering the transformation it is intended
to trigger,” Fuhlhage said.
“Materials are coming
along the way with net
zero.”
At the Expo, many
exhibitors offered environmental product declarations and third-party
certifications. The Expo
also featured a focus on
net zero energy, including
a net zero energy house
and a portion of the expo
space that operated on a
net zero energy basis.
Attendees toured
the 2014 Greenbuild
PHOTO: ATELIERS JEAN NOUVEL
CHICAGO—A residential
building in Sydney has
been named the “Best
Tall Building Worldwide”
by the Council on Tall
Buildings and Urban
Habitat (CTBUH). One
Central Park beat 87 other
international entries, and
was commended for its
visible use of green design.
Key features include hanging gardens, a cantilevered
heliostat, an internal
water recycling plant and
a low-carbon trigeneration
power plant. The building’s most visible feature,
the hanging gardens, use
a remote-controlled, dripper irrigation system and
a special process in which
the roots of each plant are
attached to a mesh-covered felt, and soaked with
mineralized water. This
allows the plants to grow
without soil along the faces
of the building envelope.
One Central Park in Sydney
Australian Tower
‘Best Tall Building’
8
A S H R A E J O U R N A L ashrae.org D ECEM BER 2014
LETTERS
Return Fans in VAV Systems
Your description of airflow tracking and direct pressure control in October’s “Return Fans in VAV Systems”
was very good. Would you recommend this approach
for an air-handling system that serves areas where
space to space pressure relationships are critical? If
so, what steps would you recommend to ensure that
the static pressure in the return duct is appropriate for
the proper operation of return air VAV boxes? I’ve seen
buildings with critical spaces and with multiple AHU’s
attempt to convert all of their systems over to direct
pressure control only to have space pressure relationships become a problem.
Brian Rose, P.E., Member ASHRAE, Guilford, Ind.
The Author Responds
You are correct and my example a) for Airflow Tracking
is misleading. Systems that have return air VAV boxes
essentially have pressure control at the zone level, typically by zone level airflow tracking (tracking the return
airflow rate with the supply airflow rate), but occasionally with zone level direct pressure control (controlling
return airflow rate to maintain zone pressure using a
zone pressure sensor). Either way, the return airflow rate
is determined by the return air VAV boxes, not directly
by the return fan, similar to a VAV supply air system. So,
the return fan simply needs to be controlled like a supply air fan on a supply air VAV system: maintain enough
negative static pressure in the return air duct to allow all
return air VAV boxes to meet their airflow setpoints. In
other words return fan speed should be controlled by
return duct pressure and not be controlled based on system level supply/return airflow differential as my article
suggests. Sorry for the confusion!
Steven Taylor, P.E., Fellow ASHRAE, Alameda, Calif.
LivingHome throughout
both days of the Expo. The
modular net zero home
that featured the latest
sustainable building techniques was relocated and
permanently placed in
New Orleans’ Lower 9th
Ward after the conference.
The Net Zero Pavilion,
which included 11 exhibitors in 1,500 ft2 of exhibit
space, was powered by
an on-site microgrid
including alternate
energy generation, storage and distribution.
The space was designed
for the hybrid use of
alternating current and
direct current and was
designed to demonstrate
the efficiency, reliability
and resiliency of hybrid
microgrids, which can
operate in combination
with the local utility grid
or in isolation from it.
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