Net Zero Roundtable
Ralph DiNola, executive director, New Buildings
Institute, Vancouver, Wash.
David Stermer, director of engineering at Metal Sales
Manufacturing Corp., Louisville, Ky.
Greg Mella, FAIA, LEED AP BD+C, vice president,
co-director of sustainability at SmithGroupJJR, Washington, D.C.
Brian Court, AIA, LEED AP, principal, The
Miller Hull Partnership LLP, Seattle
Justin Harkins, vice president, sales at Thermal
Design, Stoughton, Wis.
The push for net zero energy buildings has increased in recent
years, with the New Buildings Institute reporting that the number
of verified net zero energy buildings or those targeting net zero
energy has more than doubled in just two years, from 60 in 2012 to
160 in 2013.
The International Living Future Institute, creator of the Living
Building Challenge, even offers the Net Zero Energy Building
Certification, designed to verify the buildings that rely on energy
conservation and on-site renewables to achieve all of its heating,
cooling and energy needs.
Since net zero energy is something that we will continue to hear
more about, Metal Architecture took this opportunity to speak to
some people in the architecture and construction industries to
learn more about their thoughts on net zero energy buildings.
1. What are the most recent trends in net zero building
Ralph DiNola: The current definition of net
zero energy buildings is generally understood as those that consume
only as much energy as can be produced on-site through renewable
resources. Since space for renewable is typically limited and the
cost is relatively higher than energy efficiency measures, the
first step in achieving net zero energy performance is to design an
ultra-low energy building.
New Buildings Institute (NBI) research shows that most net zero
energy buildings have an Energy Use Intensity (EUI) under 40
kBtu/SF/year, with a national average around 20 kBtu/SF/year. The
second step to achieving net zero energy performance is to add
renewable energy systems. Most common are photovoltaics (PVs), but
multifamily projects often include solar thermal for domestic hot
Integrated design is the most critical aspect of creating a net
zero energy building. In this process, the owner, architect,
engineer and other critical roles on the design team, work in
concert to ensure that the interrelationships between the building
and its systems, surroundings and occupants make efficient and
effective use of all resources.
Under an integrated design process, key efficiency
considerations include optimizing the building envelope for thermal
efficiency, occupant comfort, daylighting and natural ventilation.
Advanced lighting strategies that include high efficiency equipment
coupled with controls and right-sized, high efficiency HVAC systems
are other measures that design teams give special attention.
Beyond the design owners and operators need to manage
plug-and-process loads, work to understand the most efficient
option for each component, and drive down those loads. Building
occupants should be educated about the energy efficiency features
of the building and engaged in what actions they can take to keep
energy use in line.
David Stermer: Recent trends include
high-efficiency HVAC and lighting, along with seasonal thermal
energy storage. Additionally, the interest in Passive House, which
features a low air permeability of the exterior envelope, is
Greg Mella: One trend is envelope
commissioning, which provides a means of ensuring that the robust
building enclosures we design-as a necessary component to extreme
energy conservation-get built and tested. We are also seeing more
performance modeling and simulation during the design process,
especially early on. To achieve net zero, performance modeling is
critical to optimize the performance of orientation, window design,
daylighting, exterior sunshading, envelope and so on. Another trend
is with energy metering information, as it's being integrated into
everything from light switches, to power strips, to systems
furniture. Monitoring behavior has a huge role in energy
consumption. Making the energy implications of the way we use a
building evident to the actual users really drives home
conservation. It even stimulates a little healthy competition!
Brian Court: Active exterior solar controls are
very effective tools building designers can utilize to minimize
solar heat gain, control glare and direct light deeper into
occupied spaces. All of these strategies help minimize energy loads
making them a vital first step toward successful net zero design.
While these systems are prevalent in Europe, they are just starting
to make inroads in the U.S. market. We will be seeing more and more
of this technology.
Justin Harkins: Recent cost reductions and
quality improvements in LED lighting are a trend that is having a
significant impact on the economics of net zero building designs.
Lighting energy consumption is generally second only to HVAC
consumption in buildings. In the past, the challenge of adopting
LED lighting often involved making sacrifices in some combination
of cost, color quality, light output and directionality that could
render them impractical for many applications. Now, there are an
increasing variety of LED lighting options that perform very well
in all of those specifications. While the lighting efficacy is not
always an improvement on florescent lighting, the life cycle cost
is reduced by long life of the LED lamps.
2. What are some design considerations with metal to
keep in mind when designing net zero energy
Harkins: Metal buildings can be a surprisingly
economical structure for net zero projects when you have an
understanding of the obstacles and how to work around them.
Unfortunately, the conventional methods of constructing metal
buildings with ineffective thermal envelope due to compressed
insulation, excessive thermal bridging due to exposed secondary
structure, and high infiltration are a poor starting
Upgrades to R-values have little impact if those additional
R-values are reduced by even more extreme compression or if the
purlins and girts are not thermally isolated. Lack of thermal
performance of conventional metal building envelopes require
corresponding increases in heating and cooling equipment capacity
that result in avoidable up-front and and ongoing costs for the
Insulating the building properly is the key to economically
reducing the energy consumption of metal buildings. This is because
the investment in insulation is either entirely or substantially
offset by other project savings, including reductions in HVAC
equipment costs. On a typical project, this can make the payback
timeframe on this investment as low as zero, which has an enormous
impact on the economics of designing to net zero.
While the costs of solar PV modules have come down drastically
in recent years, it is still more economic to invest in reducing
energy consumption first. Through a comprehensive consideration of
the insulation, HVAC, lighting, controls, internal loads, cost
trade offs and an operational plan, consumption can be reduced such
that the cost of the necessary renewable power generation equipment
becomes manageable, not just for big budget projects, but for every
day projects as well.
Stermer: There are several design
considerations architects should keep in mind, including:
- Color-solar reflectance.New color technologies are available
that provide a high Solar Reflectance Index (SRI). These colors
reflect solar energy that is usually absorbed as heat. The result
is a cooler roof and less energy needed for cooling needs.
- Roof slope and orientation, which affects the amount of solar
energy on the roof. If solar panels are being utilized, then the
roof orientation and slope should be considered. It's important to
design the roof to receive the highest amount of sunlight to
convert to usable energy. If the roof has the wrong slope or
directional orientation, there is risk that the solar panels will
not have enough exposure to sunlight to create enough usable energy
for a net zero building.
- Attachment of local energy production equipment. For net zero
buildings, it is crucial to choose an appropriate panel profile. If
a traditional solar panel is used, a ribbed panel is ideal because
the attachment hardware can be clamped to the panel ribs, therefore
eliminating the need to penetrate the panel. If a thin film solar
panel is being used, then a flat-pan panel is ideal because the
panel should be adhered to a surface that's as flat as possible.
Striations can prevent a strong adhesion.
- Metal panels are ideal for solar attachment. The panels do not
require penetrations for attachment, and the life span of metal
roofs are far beyond that of solar panels.
materials have a lot to offer net zero energy buildings. Standing
seam metal roofs provide an ideal roof surface for PV system
installation and metal siding provides a durable siding material
and effective rain screen for long lasting high performance
buildings. Exterior metal shading devices can provide effective
glare control as part of daylighting strategies.
Court: The finish and color of metal siding can
be a useful tool to either reflect or absorb the sun's energy.
Design teams should consider the potential of both.
Recent advances in coating and finishes have shown the potential
to mitigate air pollution through the application of a titanium
dioxide coating. This was first introduced to the building industry
by Alcoa [Architectural Products, Eastman, Ga.] on their Reynobond
aluminum panel product. Not only are the panels self-cleaning, but
they will actually pull pollutants out of the air near the panels,
break down into organic matter, which is then washed away with
rainfall. This type of groundbreaking coating has exciting
potential as buildings look beyond simply net zero toward
Mella: Metal exterior cladding systems and
framing is often used in sustainable design because metal can be
extremely durable, but metal also conducts thermal energy.
Designers need to be extremely mindful of thermal bridging to make
sure the super tight, highly insulated skins we create do not have
major leaks from thermal bridging. Thermally broken connection
details and strategies to ensure continuous insulation at the
building envelope become paramount.
3. What has the demand been for net zero
Court: While it's difficult to quantify the
demand, one thing that is certain is that the demand is increasing.
Where 10 years ago there were none, at least a half dozen net zero
buildings have now been built or are on the boards.
Stermer: The demand for net zero buildings
seems to be increasing at a moderate rate, although there seems to
be the highest demand in Europe. Last year Metal Sales executed
several successful net zero projects and see opportunity for more
in the future.
Mella: We're finding that more and more clients
are interested in net zero. Maybe three years ago, clients were
interested but did not think achieving net zero would even be
possible. Early innovators have demonstrated net zero
buildings are possible and a variety of scales, climates and
program types. We are even nearing the threshold where a net zero
energy building will be commercially viable in many parts of the
Harkins: The interest in net zero is certainly
increasing, but there is much more room for growth. Many people
still assume that net zero projects are only for big budget
projects and owners who have a high tolerance for payback. With a
comprehensive design approach that takes advantage of the synergies
of this type of design in a metal building, net zero can be a great
investment on a broad range of building projects.
DiNola: This trend is still nascent, but poised
to move quickly. In 2012, NBI identified 21 net zero energy
buildings in North America that we were able to verify by reviewing
energy use data. We found an additional 39 buildings that were
energy efficient enough to be net zero energy, but did not take the
step of adding renewable resources on-site. Finally, another 39
buildings were identified as working to achieve net zero energy
performance, but were either still under construction or did not
have a full year of energy use data.
In 2014, the number of net zero energy-verified projects grew to
33 including 32 buildings and one district-a set of buildings
achieving net zero energy. The number of ultra-efficient buildings
with energy performance on par with net zero energy, but without
the on-site renewables grew to 53 and the number of commercial
buildings working to achieve net zero energy rose to 127.
If all the buildings identified in 2014 achieve net zero
energy-level performance in the next two years, we will have more
than doubled the number of buildings in just four years. This kind
of growth mirrors our experience with green building and LEED.
Initially, the numbers were small, but then grew exponentially to
transform the building design and construction marketplace in favor
4. Are there areas of the country where the desire for
net zero has been more prevalent?
Harkins: The interest in net zero projects is
from coast to coast and in between.
Court: The greatest interest is in the Pacific
Northwest but examples can be found across the country and
Mella: Yes. The Sun Belt is still the most
prevalent location for net zero buildings. Our headquarters for DPR
Construction in Phoenix, and our Energy Systems Integration
Facility for the National Renewable Energy Lab (NREL) in Golden,
Colo., are good examples. The financial viability of photovoltaics
as the on-site renewable energy source in these regions with
excellent solar availability makes net zero pursuits more
achievable. But net zero projects are springing up in the least
likely of places like Seattle, a city with limited solar
availability. We have our Brock Environmental Center project under
construction in Virginia Beach, Va., which is a hot and humid
climate that puts a priority on energy-intensive cooling.
Stermer: There seems to be higher interest
levels in high population areas, such as the Northeast, West Coast
and Texas. However, with the recent federal mandate for building to
new or net zero energy standards, the desire is more uniform across
DiNola: California leads with 10 net zero
energy-verified buildings and significantly more under development
because of the Governor's leadership and policymaking in this area.
But other states are poised to follow as net zero energy policies
and practices are increasing seen as an effective means to create
resilient buildings and curb greenhouse gas emissions.
5. Who do you find is
requesting net zero buildings? Is there more interest in the public
versus private sector?
DiNola: Currently, the public sector leads in
pursuit of net zero energy performance in buildings. This kind of
trend is very similar to what we saw in the green building
movement. As public projects demonstrate feasibility and model the
potential for net zero energy design and construction practices,
private sector will follow suit.
In 2014, NBI found that of the 160 buildings that were either
verified net zero energy or targeting net zero energy performance;
26 percent were owned by private companies.
Stermer: There seems to be more interest in the
public sector due to the Executive Order that 15 percent of
existing federal buildings conform to new energy standards by 2015
and that 100 percent of federal buildings be net zero by 2030.
Harkins: The demand we have seen is more often
for public projects, though there is private interest as well. I
think this goes back to the perception that longer payback
timeframes are required. Public entities generally have a longer
time horizon, and tend to explore their options. Private owners may
not consider it based on that perception, or if they do, there are
many builders who don't understand how to do net zero economically,
because the approach is so different from conventional metal
buildings. When we have an inquiry about net zero from architects,
owners or contractors, we first try to address those misconceptions
first by walking them through our EnergyCraft Design process for
rebalancing the building design, and then provide energy analysis
of various design options to help them make informed decisions
about the energy performance of their building.
Court: There is almost an even split between
single-family residential, commercial and institutional.
Single-family clients tend to be motivated by their own moral
compass and simply want to do the right thing. Commercial projects
are either concerned with being perceived by their peers as
innovative or could be mission-driven to demonstrate environmental
concern. Institutional clients, who plan on owning and maintaining
their buildings for the life of the building have often been
motivated by life cycle cost analysis and understand that while net
zero buildings will have a higher initial construction cost, that
investment will pay dividends in the long run.
Mella: We've seen a real variety of private,
public and nonprofit clients requesting net zero. Our net zero
design for DPR Construction is a good example of a private client,
motivated by a sense of stewardship. Our design for the Energy
Systems Integration Facility at NREL is a good example of a public
client wanting to embrace federal mandates that seek net zero.
Finally, Chesapeake Bay Foundation's Brock Environmental Center is
a good example of a nonprofit client wanting to walk the talk and
encourage others to follow their leadership.
6. Do you think there will be more net zero residential
communities popping up across the nation? Why?
Stermer: Yes, because of energy codes and a
continued push to reduce environmental impact in architectural
design. At Metal Sales, we've noticed an increase in net zero
communities, multi-family housing and residences. We expect this
trend to continue with the growing push toward net zero.
Court: Yes, we see greater potential in the
private market where individuals can more easily prioritize and
make the upfront investment though, as described earlier, life
cycle cost analysis should make net zero buildings more attractive
to any entity that plans on occupying a building for a term longer
than that of the construction loan.
DiNola: Absolutely. Evidence in California and
other parts of the North America show that net zero energy
residential communities are technically feasible and cost effective
today. The state of California has a goal for all new residential
development to be net zero energy by 2020 and other states and
cities such as Vermont, Rhode Island, Salt Lake City, and
Washington, D.C., are looking at policies that will drive zero net
energy projects in their jurisdictions.
As feasibility expands for more buildings types and larger
square footage, net zero energy offers a critical solution for
addressing carbon mitigation mandates and higher resiliency in
buildings. Buildings account for about 40 percent of the carbon
emissions in the United States, but in some cities that number
approaches 80 percent. Policymakers understand that dramatically
improved efficiency for buildings will be required if we are going
to tackle the challenges presented by climate change.
Net zero energy buildings are good business as well. Developers
such as Gary Christensen of Boise, Idaho, are finding a positive
return on investment for the value of net zero energy
Harkins: There is already great interest from a
segment of the population in net zero homes, and energy
conservation. The technology advancements and economies of scale of
home automation products have increased the tools available to
homeowners to help reduce energy savings at home. Also, with
individual families the decision to reduce energy consumption is
not always primarily driven by economics alone, but can also about
social consciousness or just enjoying technology as a hobby. I
myself installed all LED lighting, photovoltaics and Energy Star
appliances in my home over the past two years. As a result, my net
electricity consumption at my home for the last four months was
only 26 kWh!
A positive aspect of this interest by homeowners is that some of
the consumer off the shelf technologies developed for that market
can be adopted for commercial metal building projects as well.
7. What do you think is the future of net
Court: Net zero buildings will continue to
become more wide spread and we are seeing interest in buildings
that are not only net zero energy but also net zero waste, water
and toxin free, most notable are buildings certified by the Living
Stermer: Products that help achieve net zero,
including efficient lighting, HVAC and heat energy reclamation will
continue to mature. Strategies, such as reduced energy use, energy
production and energy reclamation will also mature over time.
Additionally, on-site/local energy storage, or the reliance on the
grid during times of peak usage, is not necessarily reduced by
current net zero measures.
Harkins: The potential benefits of local and
distributed renewable power generation, including the impact on our
environment, energy infrastructure, dependence on foreign energy
sources, and our economy are tremendous. However, for net zero
buildings to become the norm for new construction, the economics
need to be there. Metal buildings have some unique advantages in
delivering economic energy performance, and this will be a great
asset to the industry in the coming years.
Mella: The 2030 Challenge set the building
industry on a path to achieve net zero energy for every building we
design, by the year 2030. When these targets were established in
2005, 2030 seemed like a long way away. We are now a decade closer
to that target date, and I've been extremely encouraged to see
early adopters and pioneers provide examples that net zero energy
buildings are possible. It gives me optimism that the aggressive
goal established in the 2030 Challenge can be met by the mainstream
following the path of these early examples. As the efficiency of
photovoltaic panels goes up while at the same time the costs for
PVs come down and simultaneously the cost for non-renewable
purchased energy goes up … well, we are nearing that tipping point.
And when the economy reaches that tipping point, the building
industry will have the knowledge to make a net zero energy future a
DiNola: NBI research shows that net zero energy
buildings are technically feasible and are already happening in 36
out of 50 states, across a broad range of building types and sizes
with strategies and technologies that are readily available.
Developers in California and other states are developing
speculative net zero energy buildings. I believe that this emerging
trend will become mainstream in the next decade. A growing network
of owners, developers, practitioners, contractors and suppliers are
aligning their efforts behind this next wave of sustainable
development. Like LEED, this market transforming movement is
poised to dramatic change practices in the building