How much easier is it to design energy efficient
buildings from the ground up, as opposed to retrofitting
an existing building?
KP: We have similar technologies that can be used in
both new buildings and building renovations. The primary
difference is new buildings have many more options with
orientation and building materials. Renovation projects
will typically have a fixed building footprint and some
building envelope components will be re-used.
Building geometry will also determine whether onsite
renewable energy is feasible. Hi-Rise buildings in dense
urban environments will likely need to use off-site
renewable energy, since there simply is not enough
building footprint for on-site solar PV. One to three story
buildings typically have enough roof area for on-site
solar PV to balance the energy for buildings with an EUI
of 25-30 kBtu/SF-yr.
There are some facilities like hospitals and laboratories
that are so energy intensive, that some people doubt
they can ever Zero Net Energy. Can they?
KP: What are the commonalities in hospitals and labs?
They have a lot of equipment, they tend to run 24/7 and
they’re serving some critical function. Because they’re
operating 24/7 they’re going to use more energy on
an annual basis. But the same energy efficient design
principles and technologies can apply to any building.
We can still take a hospital or laboratory and make it
substantially more energy efficient than what the code
requires. Is it practical to put PV onsite and be able to
offset the energy the building is using? Typically, no but
we can still take all the strategies from ZNE type design
and use them in hospital or lab setting. Hospital and lab
owners want the best energy efficiency possible that
makes sense for them from a life cycle cost standpoint
while still accomplishing their primary mission.
What are some specific design strategies and
technologies that you use to achieve Zero Net Energy?
KP: Passive design strategies like thermal mass,
daylighting and orientation are some examples. A
lot of the ZNE buildings that we’ve been designing
recently, have some type of mix mode operation of the
HVAC system using natural cooling when the ambient
conditions allow. With California’s mild climate, there
are times during the year when we can use natural
ventilation/cooling. It’s not much different than the way
most people operate their houses, they don’t turn on the
AC all the time if it’s nice enough outside to open the
windows.
In the last 20 years, we’ve seen a tremendous increase
in HVAC energy efficiency. Chillers, package units and
radiant heating and cooling systems have gotten much
more energy efficient.
What are some of the most noteworthy Zero Net Energy
projects that you have overseen?
KP: We’ve talked a lot about CSULB’s recently opened
CCPE (College of Continuing and Professional
Education) building but it’s a unique building because
there’s not a lot of three-story ZNE buildings in California.
The fact that CSULB decided to go ZNE with a three-story
classroom building is noteworthy. It uses mix-mode HVAC
operations with a dedicated outside air system, radiant
heating and cooling and ceiling fans. When the weather
is nice outside, occupants get a green light to open the
operable windows, the active systems turn off and the
passive systems take over.
We’re currently designing a retrofit for Cal State LA.
Building 12 is a former physical sciences building being
converted into an office building. It’s a high-rise that will
undergo a complete interior redesign. It’s being designed
as “Zero Energy Ready”, the PV panels will be added
some time after the project’s completion on a nearby
parking structure. We’re on a design-build team, and
the project design is nearly finished. I tend to find that
design-build makes a lot of sense for ZNE buildings.
You get to have discussions with the contractor and the
architect and teams tend to come up with a better set of
technologies that work and are financially viable.
Finally, I think we would all like to know, is there a
difference between “Zero Net Energy” and “Net Zero
Energy”? Which is correct?
KP: There is no difference. All these terms, along with
others, are in widespread use and mean the same thing.
Many engineers want to have the word “net” in there
because it’s technically correct, but a Zero Energy
Building is the same as a Net-Zero or Zero Net Energy
building. They all refer to the same comprehensive U.S.
Department of Energy definition.
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