the path to net zero court

8/8/2019 The Path to Net Zero Court

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W e s t b u i l di n g fa C a de

The Path to Net Zero Co2urt:

Wh fom follow pfomac.A team led by HOK and energy and daylighting

consultant The Weidt Group set out to determine

whether we could use todays technolo gy,

materials and systems to do exactly that.

Though there has been lots o talk about reducing

our societys carbon emissions, architects havent

been designing mainstream, aordable carbon

neutral ofce buildings. This has to change quickly.

HOK and The Weidt Group collaborated on this

research and design project so we could better

understand the market opportunities and barriers

related to zero emissions design. The goal was

to develop new design p rocesses that makezero carbon possible and affordable for all.

T H E P A T H T O N E T Z E R O C O

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Can we design a market-

rate, Class A, zero emissions

ofce building?


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Whyzero emissionsNTEA Ozero energy?

The team used the .. epartment o Energys

defnition o a net zero emissions building:

A buldng ha produc

and xpor a la a much

mon-fr rnwabl

nrgy a mpor and u

from mon-producng

nrgy ourc annually.

Out o this 10-month eort emerged a new proto-

type or reasonably priced, readily constructible and

marketable zero carbon emissions ofce buildings.

built, the our-story, 170,735-sq.-t. Net Zero

Co2urt would be one o the largest net zero

emissions buildings in North America.

The team discovered that we can do this now.To do so, architects must embrace the rigor,

discipline and opportunities presented by ully

integrating daylighting and energy analyses into

the design process. By developing innovative

design solutions around aspirational perormance

parameters, we can create extraordinary zero

emissions buildings. Architects must allow

orm to ollow perormance.


R T

Emissions rom buildings represent39 percent of the U.S. total.

Zero emissions orces us to thinkabout the environmental impactof the enery source.

We must get to zero emissionsto address climate chane.

The road to zero emissionsis through enery efciency.

Zero emissions is undamentalto the future of architecture.

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The team selected this site rom choices

around North America because:

St. Louis has a challeninfour-season climate.

lectricity costs in Missouri areamon the lowest in the country.

St. Louis electrical fuel proleis 8 percent coal.

The team believed that i they could create a

market-rate carbon neutral design on this difcult

site, the process could be replicated in any location.

The building site is part o an emerging biotech corridor. To the west is Barnes-Jewish

Hospital at Washington niversity Medical Center and to the east is aint Louis niversity.

mmediately to the north is the citys historic Central West End, a thriving commercial and

residential district. The site is on a bus line and adjacent to the t. Louis MetroLink rapid

transit system, near a new stop planned or the next improvement cycle.

The team designed this Net Zero Co2urt prototype to it comortably

onto a potentially developable site in midtown t. Louis.

site

N


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Temperature

Clouds

Humidity

Wind peed

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The program organized most optimally into

two our-story, 300-oot-long ofce bars

oriented east-west and joined by two links that

enclose a 60-oot-wide landscaped courtyard.

The north and south acades optimize

vision and daylight glazing with insulated

opaque areas to leverage natural light while

maintaining a high-perormance envelope.

The east and west acades are essentiallysolid, blocking glare at low sun angles and

adding to the average R-value o the

building skin.

Exterior walls o the ofce bars consist

o R-40 rain screen construction with tile

acades to the east and west. Vision and

daylight panels are triple-glazed, double-

low E with argon fll set in wood rames to

provide optimized and controlled daylight

into the workspace, views to the exterior

and maximal R-value.

On southern acades, evacuated solar thermal

tube panels provide both a unique aesthetic

and a heat source or the building. The roo is

sloped at 10 degrees south and incorporates

solar PV and solar thermal panels over an

R-50 insulated roo (R-40 walls).

A two-level, 17,375-sq.-t., daylit parking

structure provides 438 parking spaces

and is topped by rootop photovoltaic

panels and light wells.

esi sti

Early design showing PVand vegetated walls on west acades

Massing diagram Water wall garden

Roo tilted to the south

Entry rom parking


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Vegetated Wall an d ed ible gard en

The east and west acades o the links are aced with a

vegetated wall to provide aesthetic continuity to the natural

aspects o the courtyard, moderate the outdoor cl imate or

tenants and even soak up a ew additional carbon dioxide

molecules (not included in the total analysis).

An edible garden area along the south acade provides

an additional amenity or building occupants.

in tegrated system s

Because the architectural and site strategies resulted

in greatly reduced HVAC loads, the team was able to

design an in-slab radiant heating and cooling system

that is integrated with an underoor air distribution

(A) system. A radiant heating and cooling system

provides temperature control or the space. Because

the air handling systems are primarily providing onl y

ventilation, they could be greatly downsized.

The dedicated outdoor air system (OA) air handlingunits include total energy recovery wheels as well as

dehumidifcation and ventilation or building occupants.

A emand Control Ventilation (CV) system monitors

and adjusts the volume o outside air introduced into

the building based on demand. This reduces heating,

cooling and dehumidifcation loads attributed to

outdoor air.

n addition to the CV system, building automation

control strategies include photocell and occupancy

sensor control o lighting and occupant control o

plug loads.

A raised oor provides complete exibility or a

multi-tenant layout. Manually operated windows

allow or natural ventilation during the spring

and all shoulder seasons.

esi sti

ren eWable en ergy

The integrated design o Net Zero Co2urt reducedcarbon emissions by 76 percent through energy

efciency strategies, with only minor additional frst

costs compared to a conventional ofce building.

To provide the remaining clean energy required to

reach zero carbon emissions, the team i dentifed

on-site renewable energy systems that include

approximately 51,800 square eet o rootop and

wall-mounted photovoltaic panels and 15,000

square eet o solar thermal tubes on the southern

building acades and roo.

d aylightin g

Recognizing that daylighting is the single most important

way to reduce electricity and its subsequent carbon

emissions, the design solution eatures extensive use

o natural light.

An early climate and context study analyzed local solar

intensity, wind potential, temperature and humidity ranges

and cycles, and the eects o the t. Louis latitude and

building type on daylighting potential and shading options.

With 150-180 cloudy days per year classiying t. Louisas an overcast sky zone, the team designed to an 18.5

percent window-to-oor area and 35.2 percent window-

to-wall ratio to achieve a minimum 1.5 percent daylight

actor across a 60-oot-wide oor plate.

The massing, orientation, oor-to-oor height, window

sizes, quality o glass and landscaping all are optimized

to ensure that the building can be illuminated without

electricity during daylight hours and can mitigate

the carbon emissions related to electrical energy

consumption.

The trees are sized and placed to integrate with the

building in a way that optimizes the daylighting solution.

sing espaliered trees helps reduce the heat island

eect and preserves views while maintaining natural

light corridors.

Tons o CO2

avingsaylighting analysis optionsPlan o garden

View looking northwest to courtyard


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en ergy use P roJ eCtion sbased on m od elin g

The buildings energy use intensity (E) is

21.9 KTBs/ per year beore renewable

energy is considered.

Annual energy cost savings through the

buildings energy efciency, solar thermal

and photovoltaic system are $184,567,

leaving an annual energy cost o $2,418,

or 1 cent per at 2010 utility rates.

in Cen tiVes

The Net Zero Court team determined that the

project would be eliible for several one-time

overnment, city and utility company incentives:

Federal solar rebate (30% of system cost): $1,521,251

TIF - City real estate tax and % sales tax retail: $394,285

Pct tax deduction @ 3% tax rate: $107,563

merenU incentive: $105,648

merenU solar incentive: $50,000

Laclede gas: $25,000

Total one-time incentives: $2,203,747

KeY tCMes

PaybaCK

etailed cost estimates illustrate that with an

estimated construction cost o $223 per square oot,

this project is marketable and aordable.

The payback or the investment required to reach

carbon neutrality compared to a LEE-certifed

baseline building would be 12 years i the r ise in the

cost o uel outpaced general ination by 4 percent

a year. But the payback would be less than 10 years

toayin the many other areas o the country where

electricity is more expensive.

leasin g aP P roaCh

The building would appeal to engaged tenants who

would appreciate the larger volumes o open inter ior

space, access to views and natural light, landscaping

and interior courtyard. Occupying this space would

send a positive message to both the public and

employees that this organization cares about its

peoples health and the environment, and is

committed to reducing its carbon ootprint.

CENARO THAT WOL RVEPABACK OWN TO

1 years

Tenant premium of

$60K/ .0 cost/SF

(modest)

Fuel escalation rate

of 7% than discountinflation rate

Blended electricitycosts of

$0.2/kw(currently reality inseveral U.S. states)

$. million more

one-time incentives(w c c

pc c!)

Solar and PV costs

c wover time

Potential cap-and-

trade leislationand other initiativesto restrict carbon

emissions


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The process proved that designing an ofce building

the most universal commercial building type

to be carbon neutral was easier and more aordable

than most people believe. By respecting strict

perormance parameters and using them to inorm

and guide the design, the resulting site-specifc

solution also revealed a replicable process that

can be applied to most building types andregions across the world.

a Virtual d esign P roCess

Except or two in-person project kicko meetings,

the team avoided carbon emissions rom air travel

by meeting virtually. The group met or 15 intense

design sessions with many more smaller work

sessions in-between over a 10-month period.

Team members collaborated by using WebEx and HOKs

Advanced Collaboration Rooms, which enable high-

resolution videoconerencing and use o virtual ipcharts.

How to do it:

Five Steps for Designing aZero Emissions Office Building

V E E G N T E P

esign teams need to learnto design or zero carbon asquickly as possible.

HOK and The Weidt Group are sharing knowledge

gained rom this eort to help push carbon

neutral design into the mainstream.

The Net Zero Co2urt team discovered that

designing or carbon neutrality demands

integrated, uninching design and analysis.

There is no room or silos by unction or role,

and nothing is too important to be questioned,

evaluated or changed.

Team members in t. Louis and an rancisco communicatevia HOKs Advanced Collaboration Rooms

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The frst step or the Net Zero Co2urt project was to develop

an integrated team that understood the zero carbon emissions

goal and then collaborated on perormance-based decisions

through every step. Architects, engineers, energy and daylighting

analysts, urban designers, landscape architects, construction

cost estimators and the developer attended well-prepared

design meetings that began during initial goal-setting sessions

and continued through the fnal design. This was integrated

design on steroids.

Gaining inormed real-time eedback rom such a diverse group

and mining each others' insights enabled t he design team

to make aster, better decisions. The energy modelers and

daylighting analysts, or example, were able to use rich analyticaldata to challenge everything rom the type o street trees the

landscape architect wanted to speciy to the senior designers

ideas or the building massing.

Teams that are pursuing a carbon-neutral design must be willing

to explore the limits o what they believe to be true by testing

every assumption against alternatives. They also need to be open

to accepting new ideas and processes, even i they conict with

long-held belies or ways o working. ts likely that t hey will need

to leave their comort zone.

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HOK and The Weidt group have dened three Phases

and fiVe Key stePs that teams can use to desin

affordable zero emissions buildins.

ssemble a resourceful team capable of andwillin to o throuh a data-rich desin process.

stablish an iterative desinevaluation process.

or a long time, sustainably minded architects

have been pushing passive solutions frst

doing everything they can do to optimize a

buildings envelope without using a switch or

a an. or a zero emissions design, there is

tremendous value in reducing energy use by

thinking comprehensively about the massing,

envelope, lighting, HVAC systems, plug loads

and operations. Rather than moving in a straight

line rom passive to active design strategies,

the approach must be integrated and iterative.

esign teams cant make assumptions or ignore

economic realities. The team continuouslyreevaluated frst costs and the planned operating

perormance o the building. The group ollowed

a meticulous system or organizing all the data.

A local developer and two t. Louis construction

companies provided critical reality checks in the

orm o construction cost estimates and leasing

structures. This ensured that the design was

marketable and aordable.

1A 1B

V E E G N T E P

s t eP #1

o r gani z e f o r z er o Car bo n emi s s i o ns : DVLOP PLN FO LNINg ND DCIDINg.

PHAE

Pre-designs t e P # 1

o r g a n i z e f o r z e r o C a r b o n e m i s s i o n s :

dvlop a pla fo la a c.

s t e P #

aCCeP t your Con d ition s:

d vomtal, comfot a

acal oal bfo b .

PHAE

design nd OnsruiOn

s t e P # 3

resolVe the m aCro-sCale:

dvlop t a achtctal tat

that c y a optmz

y ato.

steP #4

d eVeloP in tegrated solution s:

d whol bl ytm to

tl thoh cot ba.

PHAE

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steP #5

m ain tain zero:

Pov a pla that wll qp th ow

a tat to occpy a opat th

bl wth zo mo.

HOK t. Louis HOK an rancisco Brainstorm session at The Weidt Group ofce in Minnetonka, Minn.

1TEP 3 4

PHAE

I

II

III

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NORTH

15

30

45

60

75

EAST

105

120

135

150

165UTH1 5

210

225

240

255

WEST

285

300

315

330

345

10km/h

20km/h

30km/h

40km/h

50km/hhrs

370+

332

296

258

222

185

148

111

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Reaching zero emissions requires a tremendous

amount o upront exploration and preparation.

Once the team has defned goals, constraints and

opportunities, they will need to brainstorm energy

conservation strategies. The only way to make t hese

buildings cost-eective is to make them as energy

efcient as possible beore looking to generate

energy through on-site renewables.

The Net Zero Co2urt team used an Energy Predesign

coping Tool (EPT) to do comparative modeling o

the perormance variables and evaluated more than

90 strategies during the predesign process.

An experienced energy modeling analyst can

describe the potential energy use, carbon emissions

and cost implications o hundreds o specifc energy

conservation opportunities related to envelope

insulation strategies, other envelope strategies

(rom white roo to shading eect o a PV array),

window glazing, window design, daylighting control,lighting control, lighting design, lighting technology,

cooling efciency, heating efciency, alternative

HVAC system solutions, ans and pumps, conditioning

o outside air, miscellaneous mechanical solutions,

service hot water and plug load.

n n cncn:

esi, evAAte, evise & eive

s t eP #3r es o lVe t he maCr o - s Cale:EVELOP TE AN ARCHTECTRALTRATEGE THAT RECEENERG NEE AN OPTMZ EENERG GENERATON.

Model, manae, monitor. Focus on climate in place. Optimize site and buildin surfaces.

The Net Zero Co2urt teams mantra was, model,

manage, monitor. They created a model o a virtual

building, measured the perormance at every step o

the design and managed expectations until they

designed a real building that works. This approach

ensured that every design decision contributed to

the zero emissions goal.

Aesthetic decisions made with the best intentions may

seem perectly fne, but i they compromise perormance,

by even a small amount, the ailures will be multiplicative

and cause death by a thousand cut s.

Buildings have complex interactive behaviors, which

means the design solution or one project wont be

the same or another. Though a team should not go on

intuition or rely solely on past experience to design or

zero emissions, solutions likely will include an emphasis

on energy efciency and daylighting, which always will be

more cost-eective than renewable options.

evelop the building massing and orientation that

take ull advantage o the local solar, wind and

water resources. urther refne this solution in

section and plan to optimize the use o available

resources and reduce loads. ou will need to model

the daylighting savings oset by the energy penalty

o increased oor-to-oor and glass area.

Every square oot o the building surace should

be used or a unction, either as a consumer or

producer o energy. The photovoltaic panels and

solar thermal tubes on Net Zero Co2urt can act as

the roo or acade, and as shading devices.

Build task-specifc simulation models that compare

and evaluate massing and orientation options.

Balance perormance and cost or the right mix

o solar gain, shading, daylighting and renewable

energy generation. Rigorously track key data on

emissions, frst costs and operating costs.

3A 3B 3C

V E E G N T E P

Virtual building models Massing model sing all building suraces or a purpose

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n n cncn:

esi, evAAte, evise & eive

s t eP #4deVelo P i nt egr at ed s o lut i o ns :ENE W HOLE BLNG TEMTO TNNEL THROGH COT BARRER.

Develop secondary systems andoperational expectations.

xamine the sets of whole buildindata and repeat the process.

This includes controls and control scenarios or

lighting, plug and occupancy loads, comort and

security settings, and ongoing metering, monitoring

and accountability systems.

eveloping a plan and installing technologies

or carbon neutral operations is as important

as designing the potential to do so.

ont expect a solution to be perect on the

frst pass. Teams should regularly revisit steps

3 and 4 in order to resolve the unexpected

results that will occur.

or reasons o cost or perormance, teams may

need to review and adjust the zoning o the building

envelope or opaque suraces, glazed areas,

ventilation access, living suraces, shading,

solar hot water and photovoltaic areas.

imilarly, the cost and unctional value o MEPsystems and controls will beneft rom anot her

set o models or a team to measure its progress

against and then manage the perormance o the

design and the clients expectations.

4C

4DDevelop, evaluate and select primaryarchitectural, MP and structural systems.

Once a team has maximized the energy efciency o

the building being designed, they can get the rest o

the way to zero emissions through on-site renewable

energy sources.

esign teams should use energy and apply dierent

renewable energy sources as optimally as possible.

The principle o entropy states that energy can be

more or less concentrated. A design will be most

efcient i it can meet a buildings energy needs with

similar energy states. n other words, use energy inthe orm it is in: heat as heat and light as light. t will

be more efcient, or example, to use natural light or

daylighting than to convert it to electricity or heating

or powering ans. Otherwise, there can be a dramatic

loss in efciency that adds to a buildings emissions.

The cost tunnel eect theorizes that the cost o

adding energy efcient equipment to a building

increases as the design team tries to squeeze in

more technologies. But i a team can shape the

architecture to reduce the need or technologicalsystems while achieving efciencies o at least

70 percent, the cost begins to go down.

Beore beginning design, the Net Zero Co2urt

team evaluated energy use data or similar buildings

to set an energy efciency target o 80 percent

compared to a benchmark ofce building in the

t. Louis climate region. Comparative analyses

guided all decisions, major or minor, by explicating

emissions data. ubsequent iterations refned the

initial decisions and defned a solution that reached

73 percent energy use reduction (KTB/)

with energy efciency.

Once the envelope and orientation are tightly bracketed

or resolved, the team should develop comparative data on

mechanical system design and zoning alternatives.

ts important to test and refne envelope insulation levels.

Whenever possible, simpliy system operations and avoid

solutions that require high an energy and re-heating.

esign components that serve multiple purposes. Radiant

heating or cooling suraces, or example, could be part o

the structure or ductwork could serve as light shelves.

4B

V E E G N T E P

Use enery in the form it is in.4A

ntropy: sing heat as heat and light as light Brainstorm session at The Weidt Group ofce in Minnetonka, Minn.iagram explaining how orm ollows perormance

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Net Zero Co2urt secret garden

wp:

CCACY & eAti

s t eP #5mai nt ai n z er o : PROVE A PLAN THATW LL EP THE OW NER AN TENANTTO OCCP AN OPERATE THE BLNGW TH Z ERO EMON.

Provide the owner with a calibration plan.

Models and baselines each play a role in ongoing

perormance. Just as the weather will vary rom

year to year, so will the behavior o the users and

operators o a building. Monitoring consumption data

such as the Energy tilization ndex (E) will not tell

the whole story o how a building is perorming.

To maintain the balance o emissions, recalibrate

perormance expectations to address and predict

the eect o potential changes over time.

Buildings dont use energy, people do. With estimates or

the energy use that can be attributed to tenant consumption

ranging rom 50 to 75 percent, the design team will need to

understand the diversity o the owners team and determine

how they intend to deploy sta and operate the building.

Their behavior during the buildings operations will make

or break a zero emissions design.

nderstanding the lines o responsibility and accountability

will allow teams to provide technology and service that allow

or clear monitoring, measurement and management o

the buildings perormance and provide occupants with the

tools and knowledge to ully participate in energy conservation.

Plug loads will be a huge variable in a zero emissions,

multitenant speculative ofce building. Teams cant aord

to let them oat. tudies show that people are using rom

25 to 60 percent o a typical installed plug load. or this

project, the team made assumptions that the plug loads would

be 30 percent lower than ound in a typical ofce building.

nstalling sub meters will allow teams to monitor usage and,

using a carrot-and-stick approach, reward tenants who come

in under and require tenants to purchase carbon credits i

they surpass a predefned monthly usage allocation.

or now, the type o tenants a zero emissions ofce building

would attract likely would be motivated to participate in this

positive environmental story and be willing do the right thing

by accepting a reduced equipment load in order to help

control the emissions.

5B

5A

esigning orzero emissions requires designers to rethink design processes

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V E E G N T E P

econize that occupants are a criticalpart of a carbon neutral desin solution.

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Rethinking

How we design buildings

L E O N L E A R N E

W e s t b u i l di n g e n t ry

myth #1:

All-glass buildings are the future of

low-energy and low-emissions design.

Though daylighting is the single-most

important way to reduce electricity

and carbon emissions, carbon neutral

design requires a precise balance o

light and heat. To determine the rightcombination o energy-efcient glazing

and insulated wall panels, the Net Zero

Co2urt team modeled the daylighting

savings oset by the energy penalty

o increased oor-to-oor and glass

area. These calculations revealed

how much glass to use.

myth #:

We cant go wrong by planting trees.

The team quickly discovered that placing

trees in the wrong places would impede

the daylighting solution. The landscaping

must preserve access to natural light

and be completely integrated with

the building design.

myth #3:Photovoltaic panels are effective

only in bright, sunny, warm climates

like in California. Though the teams

climate analysis showed that there

are 150 to 180 cloudy days per year

in t. Louis, there is more than enough

sun to generate the required on-site

solar power. The team also learned that

solar panels are more efcient in cooler

climates heat is their enemy.

myth #4:

We cant design a zero emissions

building to be taller than three stories.

This team designed our oors.

Admittedly, they needed to use the

roo surace o the parking structure

to house 17,000 square eet o

photovoltaic panels.

myth #5:

Zero emissions isnt possible for

a conventional project budget.

etailed cost estimates calculated

the construction cost to be $223 per

square oot. Annual energy cost savings

through energy efciency and solar

power will be approximately $185,000.

The payback or the investment to reach

carbon neutrality compared to our baseline

building would be 12 years i the rise in

uel costs outpaces general ination by

4 percent a year. The payback would be

less than 10 years today in the many

other areas o the .. where electricity

is more expensive. Policy changes

supporting low-carbon and low-energy

initiatives, including additional ederal

and state incentives or renewable

energy, could bring zero emissions

buildings much closer to our grasp.

Desinin for zero emissions requiresus to rethink how we desin buildinsand demands a rigor that remains rarein the design and construction industry.But with about 40 percent o the greenhouse gas emissions

contaminating our atmosphere coming rom buildings, we have no

choice but to begin a concentrated eort to do things dierently.

The challenge or design teams is to think about perormance

beore we draw and to embrace the limits presented by the

daylighting and energy analyses. We need to know when weare making purely aesthetic decisions versus science-based

decisions and be clear about which is which. Within these strict

perormance parameters lies the reedom to design.

MTHBUSTS FO ZO MISSIONS DSIgN

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m a l, aia, leed aP bd+C

211 N. Broadway, uite 700

t. Louis, MO 63102

[email protected]

314.754.3927 tel

dv a. ej, faia, leed aP bd+C

5800 Baker Road, uite 100Minnetonka, MN 55345

[email protected]

952.938.1588 tel

Project TeamContaCt

Breakthrough desig does't just hae.

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Get the 123 Zero Build app for

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LL CO NT NT CO PIgH T 21 H O K gO U P ND TH W IDT gO U P. LL IgH TS S V D.

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the path to net zero court

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