Editor, Laboratory Design
Laboratory Design spoke to Ian Dempster, senior director of product innovation at Optimum Energy and a certified energy
manager (CEM), about HVAC considerations
when planning a net zero building.
Laboratory Design (LD): What is the
HVAC system’s role in a net zero building?
Ian Dempster (ID): I remember years ago
(pre-2010), talking to an engineer whose
passion was net zero buildings, and he
was very dismissive of optimizing current
HVAC systems. He believed that a true
“green” or net zero building didn’t need
HVAC, or at least systems as they currently are conceived. I didn’t agree with that.
First, there is no easy path for the current
existing building to become net zero, so
it has to be done in stages. Improving
buildings and building systems over time
is essential, but people want to be comfort-
able, and in a working environment that is
a necessity for productivity. Even brand-
new buildings have to have some means of
keeping their occupants comfortable; so
at the end of the day the role of the HVAC
system in a net zero building is to keep the
interior environment comfortable, as effi-
ciently as possible, using the least amount
of energy possible. You can do this by using
new software that allows you to run these
systems holistically, utilizing the [newest],
most efficient equipment, and making
intelligent use of options like natural venti-
lation and energy recovery.
LD: What are some challenges faced along
the way, and how can they be overcome?
ID: The challenges are many and varied.
Some involve perceptions of how hard
or expensive it will be to build a net zero
building. The way to get around that is with
examples of successful projects. There have
been a good many net zero buildings finished to great success in the last few years.
Sharing those successes, and the designs
and costs, will go a long way toward chang-
ing perceptions. Looking at the building
operation costs over time will address the
expense argument. Energy use becomes one
of the major operating costs of a conven-
tional building, so you can easily show pay-
back over time with a net zero building.
Then there is the argument that older
buildings will never be net zero. There will
always be buildings whose age and initial
design make them almost impossible to
convert to net zero without major rebuilds
and total equipment replacements, but they
can still achieve lofty sustainability goals
by upgrading over time, starting with modern control systems and optimization of
existing equipment and systems.
LD: What energy efficiency/sustainability
efforts must been made?
ID: Understanding the building as an
entire connected system versus separate
unconnected systems is essential. This
starts with constructing a full energy
model of the building that includes all
systems, uses and seasons. It is important
to also model what waste the building will
produce and make plans for utilizing or
recycling that waste. Strategies like reusing
grey water for irrigation, toilet flushing or
cooling tower make-up water, and recovering heat from HVAC or wastewater, can
HVAC’s role in the net zero facility
Integrating energy-generation technology into a net zero building is essential—for example, solar PV on the roof and parking lots. Image: Shutterstock