NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

The Road to Net Zero

Bill Glover 

Deputy Laboratory 

Director and Chief 

Operating Officer

The Sustainable 

Operations Summit

May 16, 2011

NREL/PR-6A42-51124
NATIONAL RENEWABLE ENERGY LABORATORY

Vision

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• A showcase for sustainable, high-performance design

o Incorporates the best in energy efficiency, environmental performance, 

and advanced controls using a “whole building” integrated design 

process

• Serves as a model for cost-competitive, high-performance 

commercial buildings for the nation’s design construction, 

operation, and financing communities

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Research Support Facility Vision
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Design-Build Process

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• Encourages innovation

• Reduces owner’s risk

• Faster construction and 

delivery

• Better cost control

• Makes optimal use of 

team members’ expertise

• Establishes measurable 

success criteria

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Why Performance-Based Design-Build Works
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What Shaped Our Strategy?

• Manic focus on energy performance

• Design and culture dictate energy 

performance

• Whole building approach to 

integrate design solutions

• Owner/Subcontractor dialogue 

encourages creativity and trust

• Superior project definition reduces 

project risk and cost to all

• Traditional design-bid-build 

approach would not work

Key Components of Performance- Based Strategy

• Performance-based request for 

proposals

• National competition for conceptual 

design

• Design-Build acquisition strategy

• Power Purchase Agreement 

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Strategy for Superior Energy Design
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Developing a Performance-Based Request for 

Proposals Tier 1: Mission Critical Goals 

• Attain Safe Work/Design 

• LEED Platinum 

• Energy Star “Plus”

Tier 2: Highly Desirable Goals 

• 800 Staff Capacity 

• 25k BTU/sf/year 

• Architectural Integrity 

• Honor Future Staff Needs 

• Measurable ASHRAE 90.1 

• Support Culture and Amenities 

• Expandable Building 

• Ergonomics 

• Flexible Workspace 

• Support Future Technologies 

• Documentation to Produce “How To” Manual 

• Allow Secure Collaboration with Visitors 

• Completion by 2010 

Tier 3: If Possible Goals 

• Net Zero Energy 

• Most Energy Efficient Building in the World 

• LEED Platinum Plus 

• 50% Better than ASHRAE 90.1 

• Visual Displays of Current Energy Efficiency 

• Support Public Tours 

• Achieve National and Global Recognition and Awards 

• $64M project cost limit

• Up-front planning 

drives success

o Design charrettes

o Design Build Institute of 

America

o Owner’s representatives

• Design challenge

o Suite of performance 

goals to challenge team

o Substantiation criteria
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How Do You Get to Net Zero?

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• First, focus on energy efficiency 

features. 

• Then, focus on adding renewable 

energy into the equation.

• Unlike traditional design where 

architecture defines the form and impacts 

the function of a building, energy 

performance requirements drove the 

RSF.

• Extensive energy modeling 

established the basic building architecture 

and structure.
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• 25 kBtu/ft2/yr for standard office space occupant density and data 

center loads

• Normalized up to 35.1 kBtu/ft2/yr for better space efficiency and to 

account for full data center load

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Design Requirements

CBECS – Commercial Buildings Energy Consumption Survey

HPB – High Performance Building

EPA – Environmental Protection Agency
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Energy Consumption in the United States

Source: U.S. Department of Energy, 

Buildings Energy Data Book, 2006
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Energy Modeling

Space Heating

25%

Space Cooling

3%

Pumps

1%

Ventilation Fans

6%

Domestic Hot 

Water

3%

Exterior Lights

Lights 0%

6%

Office Plug Loads

23%

Task Lights

0%

Data Center 

Equipment

32%

Data Center 

Cooling

0% Data Center Fans

1%

NREL RSF Energy Use Breakdown

End Use kBtu/ft2

Space Heating 8.58

Space Cooling 0.85

Pumps 0.48

Ventilation Fans 1.88

Domestic Hot Water 0.90

Exterior Lights 0.12

Lights 2.07

Office Plug Loads 7.87

Task Lights 0.10

Data Center Equipment 10.65

Data Center Cooling 0.02

Data Center Fans 0.20
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Key Design Strategies

• Optimal orientation and office space layout

• Fully daylit office wings with highperformance electrical lighting

• Continuous insulation precast wall panels 

with thermal mass

• Operable windows for natural ventilation

• Radiant heating and cooling

• Outdoor air preheating

o Transpired solar collector

o Data Center waste heat

o Exhaust air heat recovery

o Crawl space thermal storage

• Aggressive plug load control strategies

• Data Center outdoor air economizer with 

hot aisle containment

• Roof top- and parking lot-based PV
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Building Efficiency Features

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Back to the Future

• Daylighting

• Thermal Mass

• Natural Ventilation
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Daylighting

• Two long 60-foot wide wings 

with east-west orientation

• Design reduces electrical 

lighting
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Daylighting: Light Louvers

A light louver

daylighting system 

reflects sunlight to 

the ceiling, creating 

an indirect lighting 

effect.

Fixed sunshades 

limit excess light and 

glare.
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Daylighting • Light enters through the upper 

glass and highly reflective 

louvers direct it toward the 

ceiling and deeper into the 

space. 

• Light-colored, reflective 

surfaces and low cubicle 

heights permit the penetration 

deep into workspaces.
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Thermal Mass • Incorporates many passive 

heating and cooling 

techniques.

• Six inches of concrete on the 

interior provides thermal 

mass that helps moderate 

internal temperatures year 

round

.

• Nighttime purges in summer 

months trap cool air inside, 

keeping temperatures 

comfortable for the warm 

summer days.
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Labyrinth

Labyrinth Thermal Storage

• Massive, staggered concrete 

structures in the basement crawl 

space stores thermal energy to 

provide passive heating and cooling 

of the building. 
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Natural Ventilation

• During mild weather, 

operable windows allow 

for natural ventilation.

• Automatic windows are 

controlled and operated 

primarily to support 

nighttime precooling.

• Occupants are notified 

when conditions allow 

for manual windows to 

be opened.
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Triple-glazed windows with 

individual overhangs 

maximize daylighting and 

minimize glare, as well as 

heat loss and gain.
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Window Technologies

The west elevation windows feature NREL-developed electrochromic

technology in which the windows tint in response to a small electric current, 

reducing heat gain in the afternoon hours. 

Thermochromic windows on the eastern balcony windows react to 

temperature change and have glass resistant to heat transfer. 
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Radiant Heating/Cooling

• Office wings are 

hydronically heated and 

cooled using radiant 

ceiling slabs.

• Five zones in each wing 

of the building are 

controlled by the Radiant 

Zone Control Valves.
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• 42 miles of radiant 

heating tubes run 

through the ceilings 

throughout the building.
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Ventilation system • Ventilation air is distributed 

by an under-floor air 

distribution system

• Carbon dioxide sensors 

respond to occupancy and 

control ventilation when 

needed

• Evaporative coolers 

provide cool ventilation air 

when needed

• Sensible heat recovery 

system captures either 

warm or cool air from the 

exhaust air system to 

precondition the outdoor air 

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RSF I and II 

increase NREL’s 

South Table 

Mountain square 

footage by more 

than 50% but 

increase campus 

energy use by only 

10%. 

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Green Data Center

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What Makes the Data Center Special? • Hot aisle containment • Reuse of Data Center waste heat • Hybrid cooling system • State-of-the-Art power systems • Energy efficient equipment
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• The Air Intake 

System brings in 

outside air for the 

majority of the Data 

Center’s cooling 

needs.
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Comparison of NREL Data Centers

Power Usage Effectiveness Watts Per User

Cooling + Power + Equipment

Equipment

PUE= 

0

0.5

1

1.5

2

2.5

3

3.5

RSF

17/1

1.1

3.3

PUE

RSF

17/1

PUE

0

50

100

150

200

250

RSF

17/1

42

217

Watts/User

RSF

17/1

Watts/User
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Results: 81% Reduction in Power Requirements

Data Center Watts/

User

kW/

User/Yr

# Users Data Center 

kW/Yr

CO2 Emissions 

(in pounds)

Electricity $$

17/1 217 1,901 2,100 3,991,932 5,987,898 $ 399,193 

RSF 42 368 2,100 772,632 1,158,948 $ 77,263 

Diff (175) (1,533) (3,219,300) (4,828,950) $ (321,930)
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RSF Power Generation

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NREL Campus
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RSF Net Zero Energy PV Arrays

450 kW

1146 kW 418 kW

524 kW

RSF Visitor 

Parking Lot

RSF II

RSF I

RSF Staff 

Parking Garage
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-150

-100

-50

0

50

100

150

200

12:00 AM 3:00 AM 6:00 AM 9:00 AM 12:00 PM 3:00 PM 6:00 PM 9:00 PM 12:00 AM

Power (kW)

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450-kW Roof-Mounted PV Installed and Operational 

December 2010

Hitting Zero!
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People

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People

Even with high-performance, innovative building 

features, we have found that 30% of building 

performance is related to occupant behavior.
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Removing desktop 

printers saves 

~460 Watts/Printer

LED task lights 

6 Watts

Fluorescent task lights 35 Watts

Desktop Computer (Energy Star)

300 Watts

24” LCD Energy Efficient 

Monitors

18 Watts

Typical 19”-24” Monitors

30-50 Watts

Laptop 

30 Watts Removing personal space heater 

saves 1500 Watts

Energy efficient workspace....requires new 

occupant behavior 

VOIP phones 2 Watts

iGo Power Smart Towers

Reduces “vampire” energy use

Multi-function Devices 

100 Watts (continuous)

Workstation load – 70W;

300W continuous power draw 

per person (entire building)
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The RSF is a living 

laboratory – energy 

usage is continuously 

studied and adjusted 

as needed.
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What are we monitoring? • Everything! o Lighting o Heating o Cooling o Plug Loads o Data Center o Daylighting o Mechanical System Power 

Density

o Outdoor Air Temperature o Monthly End Use Energy 

Consumption

o Elevator Lighting o PV Output

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Energy Usage and Data
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RSF Weekday Plug Load Power Density

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0 2 4 6 8 10 12 14 16 18 20 22 24

Power Density (W/ft2)

Time of Day

Model Average

October 2010

November 2010

December 2010

January 2011

February 2011

March 2011

April 2011
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RSF II

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RSF II

• 138,000 sq. ft.

• 525 occupants

• $39 million expansion

• Building 17% more 

efficient than the RSF

• Cost savings of 5%

• Completion scheduled 

for end of 2011
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Small Improvements, Big Difference

• More efficient solar panels were purchased 

at a lower cost 

• Less window area, while still fully 

daylighting office spaces 

• Larger transpired collector, creating more 

"free" warmed air 

• Better thermal breaks in the window 

frames, leveraging the latest in commercial 

windows and aluminum frames, driving 

down energy consumption and increasing 

comfort 

• Displacement ventilation in conference 

rooms, improving thermal comfort 

• Natural passive cooling in stair wells vs. 

mechanical ventilation in the RSF 

• Daylighting controls in day-lit stairwells, 

allowing enhanced energy savings during 

the day
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Sustainability and Recognition

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Reclaimed natural 

gas piping serves 

as support for the 

building. The lobby and other 

common areas feature 

beetle-kill pine from 

Western forests.

Daylighting reduces 

the need for the use of 

electrical lighting.

Anticipated 

LEED Platinum 

rating, version 

2.2 – 59 points.
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Aggregate in the foundations 

and slabs came from 

the demolition of 

Denver’s previous airport. 

Crushed recycled 

glass used in the 

stormwater management 

basins outside the 

building.
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• Major national news stories about 

the RSF

o Popular Science Online (7/6/11)

o New York Times Online (2/14/11), 

New York Times Online (2/15/11)

o Associated Press Wire Story 

(2/23/11)

o Wall Street Journal (2/28/11)

• Total award count – 20

o Engineering News Record 

(ENR)

– 2011 Award of Excellence

– 2010 Newsmaker Award

o McGraw-Hill Construction, 

Outstanding Green Building, 

2010 

o American Institute of Architects 

(AIA), Top Ten Green Project

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National Media and Recognition
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How Did We Do?

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How Did We Do?

What We Wanted

• 800 employees

• LEED Platinum

• 50% better than ASHRAE 90.1-

2004

• Net zero energy goal

• Replicable whole building design 

process

• Competitive cost for Class A space

• As many Mission, Desirable, and If 

Possible goals as achievable 

What We Got

• 825 employees

• LEED Platinum (59 Points)

• 50% better than ASHRAE 90.1-

2007

• Net zero site energy using 

photovoltaics

• Documented design process

• 220K gsf @ $259/gsf of Class A 

space

• Every Mission Critical, Highly 

Desirable, and If Possible 

performance goal achieved

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Building completed 130 days early
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Construction Costs 
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www.nrel.gov/rsf