ASHRAE Journal - February 2022 - 8

LETTERS
Existing Building
Automation System
Challenges
Many thanks for the column on
challenges in existing building
control systems in the April 2021
issue compiled from interviews by
Journal Managing Editor Mary Kate
McGowan. I am a member of the
New York City Energy Conservation
Code Advisory Committee for the
2020 code and the New York City
Mechanical Code Committee for the
2022 NYC Construction Code.
I appreciate your relaying helpful
anecdotes in this column on
controls. Many of these mirror my
own experience in a practice that
has evolved from design for new
construction of iconic buildings to
carbon emissions-focused retrofits
of existing buildings.
The last section of the column
advises designers to avoid leaving
in place independent controls
that may cause conflicting operation
at the time of a BMS rollout
or upgrade. The column gives the
example of a perimeter heating system
with controls that are independent
from a cooling system in the
same space. That condition would
represent a violation of a requirement
of Standard 90.1-2004 and
later. Section 6.4.3.2 of Standard
90.1 requires interlocks, programming,
mechanical stops or similar
to prevent the heating setpoint from
exceeding the cooling setpoint at the
zone level.
Under most applications of the
International Existing Building
Code (IEBC), International Energy
Conservation Code (IECC) and the
alteration provisions of Standard
90.1, alterations to an existing HVAC
8
ASHRAE JOURNAL ashrae.o rg
zone-physical reconfiguration of
the zone or a replacement of the
cooling or heating controls in the
zone not constituting a repair-trigger,
in my opinion, a requirement
for the zone controls to comply as
new. That would include a requirement
to comply with section 6.4.3.2
of Standard 90.1 (or provisions of the
IECC with identical effect).
Replacement, for example, of
pneumatic, analog electric or standalone
digital controls of a VAV box
with a networked DDC controller as
part of a BMS rollout would trigger
the requirement to extend the control
system to cover the perimeter
heating system serving the zone in
order to comply with the setpoint
overlap provisions of Section 6.4.3.2.
The requirement to provide setpoint
overlap restriction exists even
though such controls' work is not
ordinarily filed for permit and even
if the designer or owner did not initially
intend to include the perimeter
heating system in the project
scope.
My point is that complying with
the advice given in the last section of
the column isn't just a good idea, it's
the law.
Daniel Bersohn, P.E.,
Associate Member ASHRAE, New York
The Contributor Responds
Thanks for the feedback about
the column and for the important
work you do serving New York. You
provided a great walk-through in
your response about how modern
ASHRAE standards and energy codes
should lead to the suggested and
more-efficient outcome proposed in
the column.
Where energy codes have been
adopted, I completely agree that we
F E B R U A RY 2022
have a responsibility to communicate
and protect these strategies as a
requirement, not just good practice.
As we discuss this topic at a national
and global scale, we mustn't forget
the significant diversity of adopted
code requirements. As one example,
there are cities where energy code
has not been adopted at a local level
when decided by " home rule. " If a
region chose not to adopt this code
requirement, decisions like tying
those previously independent VAV
and perimeter heat systems together
would not be required by law-still
left to the discretion of the design
team and owners.
I continue to be amazed at how
much value energy codes have
delivered across the building portfolio
over time, but there is clearly
still room for improvement with
understanding and application. One
intention of the original column was
to highlight the reality that, even
despite the presence of our codes
and our best intentions, we still
experience this kind of disconnect
in common practice.
Independently controlled systems
serving the same space may be more
of an issue when retrofitting existing
buildings in phases, as the designer
has some natural disadvantages:
1) not being as intimately familiar
with what was originally intended/
installed and 2) being paid to focus
only on an incomplete scope. Things
simply get missed. I hope that by
sharing lessons learned about common
pitfalls and impacts of those
decisions, we might raise awareness
and help improve performance,
whether technically required or not.
Christopher Benson, P.E.,
Member ASHRAE, Salt Lake City
http://ashrae.org
ASHRAE Journal - February 2022

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