NET ZERO ENERGY
BUILDINGS
DR. CY YAVUZTURK, PH.D, C.E.M.
COLLEGE OF ENGINEERING ARCHITECTURE
AND TECHNOLOGY
DEPARTMENT OF MECHANICAL
ENGINEERING
BACKGROUND
 Assistant Professor in Mechanical Engineering
 Teach and Conduct Research in
 Thermodynamics, Heat Transfer, Energy Engineering, HVAC,
Sustainable Design
 Active Member of the American Society of Heating,
Refrigerating and Air Conditioning Engineers
(ASHRAE)
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Chair of Solar Energy Utilization Subcommittee
Former Chair of Research of Geothermal Energy Utilization
Subcommittee
OUTLINE
 An Overview of the Energy Consumption ‘Landscape’
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in the US.
Significance of Energy Savings in Buildings
What is a Net Zero Energy Building (NZEB)?
Active and Passive Approaches to Net Zero
New Constructions and Retrofits
Primary Technologies
Design for NZEB
Conclusions
Resources
AN OVERVIEW
 United States Consumed about 100 QUADs
(Quadrillion BTUs) of Energy in 2007.
 100 QUADs = 100,000,000,000,000,000 BTUs

In Other Words
800,007,000,000 gallons (US) of gasoline
 3,040,026,600,000 liters of gasoline
 3,600,000,000 tons of coal
 97,043,400,000,000 cubic feet of natural gas
 29,307,100,000,000 kWh of electricity
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AN OVERVIEW
 Energy Consumption by Source (DOE Energy Data Yearbook 2007)
AN OVERVIEW
 Where Do We Consume Energy? (DOE Energy Data Yearbook
2007)
AN OVERVIEW
 Building Energy Consumption Distribution (DOE Energy Data
Yearbook 2007)
ENERGY SAVINGS IN BUILDINGS
 Approximately 48 QUADs consumed in Buildings
 36% Space Air-Conditioning -> 17.3 QUADs
 27% Space Illumination -> 12.9 QUADs
 14 % Water Heating & Refrigeration -> 6.7 QUADs
 11 % Electronics & Computers -> 5.3 QUADs
 2% Cooking -> 1 QUAD
 10 % All Other Consumption -> 4.8 QUADs
 Significant Opportunities in Reducing Energy
Consumption Exist!
 1% Reduction = 0.48 QUADs
ENERGY SAVINGS IN BUILDINGS
 0.48 QUADs = 480,000,000,000,000 BTUs
 In Other Words
3,843,360,000 gallons (US) of gasoline
 14,592,127,680 liters of gasoline
 17,280,000 tons of coal
 465,808,320,000 cubic feet of natural gas
 140,674,080,000 kWh of electricity
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 However, Technology is available & Economics are
favorable to do more than reducing Consumption.
 Reduction coupled with Production of Energy,
leading to Net Zero Energy Buildings.
JUSTIFICATION FOR NET ZERO
 71% of All Electricity Consumed is Consumed in
Buildings! This is a Huge Burden on:
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Electrical System
Energy Resource Availability
Emissions
Economic Viability
 To make things worse:
 The Commercial Sector is Expected to Grow by Average 1.5%
Annually in the next Decade
 Economic Expansion and Population Growth Demands more
Building Space
 Energy Demand is Growing faster than Energy Conservation
Measures taken.
JUSTIFICATION FOR NET ZERO
 Consider the following (DOE 2006 Scenario):
 The current stock of commercial buildings have an approx.
Energy Use Intensity (EUI) of about 85 kBTU/sqft
 If all buildings in the commercial stock had been designed
using the Model Energy Code (ASHRAE Std. 90.1-2004), the
EUI would be about 50 kBTU/sqft
 41% Energy Savings!
 Tremendous Potential for Energy Savings Already Exits.
 And, if PV were to be added to commercial roofs EUI may be as
low as 35 kBTU/sqft!
 Add ‘Solar Energy Measures’, HVAC Equipment Efficiency
Improvements (mostly modest!) -> EUI further reduces to 15.5
kBTU/sqft
NET ZERO ENERGY BUILDINGS
 GETTING CLOSER!
NET ZERO ENERGY BUILDINGS
 BUT THERE IS SIGNIFICANT WASTE!
NET ZERO ENERGY BUILDINGS
 ZERO is the Crossover Point between a Building
that consumes a Resource and one that produces the
Resource.
 It is the point where Energy Needs of a Building has
No Impact.
 Zer0 - Sum of All Energy Flows are Equal but
Opposite.
∑E=0
NET ZERO ENERGY BUILDINGS
 Several Definitions (or ways of accounting) Exist:
 Net Zero Site Energy Building – Produces as much
renewable energy as it uses in a year at the site.
 Net Zero Source Energy Building – Produces (or
purchases) as much renewable energy as it uses in a
year when accounted for at the source.
 Net Zero Energy Costs Building – Receives as much money
from the Utility Co. for on-site production of
renewable energy as it pays in a year for energy
services.
 Net Zero Energy Emissions Building – Produces (or
purchases) enough emission-free renewable energy to
offset emissions from all energy used in a year.
NET ZERO ENERGY BUILDINGS
 No ‘Best’, All-Encompassing Definition Exists!
 Each Approach has Merits as well as Drawbacks
 Goals of the Building Owner and Building Use
Characteristics also play a significant role as to what
approach may be the most reasonable.
 However, one Rule remains constant for newconstructions and retrofits:
 REDUCE DEMAND FIRST, SUPPLY SECOND!
PASSIVE APPROACH TO NET ZERO
 Building Geometry and Orientation Measures
 High-Performance Building Envelopes (Insulation,
Fenestration)
 Passive Solar Heating/Cooling (Trombe Walls,
Fabric Cooling)
 Day-Lighting
 Natural Ventilation
ACTIVE APPROACH TO NET ZERO
 High-Efficiency HVAC Equipment
 Ground-Source Heat Pump Systems
 Solar Thermal
 Solar Photovoltaics
 Wind Turbines
 Ocean Water Cooling
 Biomass Energy
 Combined Heat and Power
 Evaporative Cooling
OTHER APPROACHES TO NET ZERO
 Thermal Energy Storage
 Controls
NEW CONSTRUCTION & RETROFIT
 Approaches to Net Zero will be different if New
Construction or Retrofit.
 Some Technologies may be ‘too late’ for an already
existing building.
 Nevertheless, with exceptions, the overall design
approach is fundamentally the same.
 It’s all about judicious use of energy to reduce cost
and ‘save the planet’ in the process!
THE FUNDAMENTALS
 A Building’s Energy Consumption can be broken
into:
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Envelope Needs
Sensible Conduction
 Solar Loads
 Infiltration Loads (Sensible and Latent)
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Occupant Needs
Sensible and Latent Needs
 Fresh Outside Air Requirements
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System Efficiencies
Mechanical Component Efficiencies
 Configuration and System Control Strategies
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THE FUNDAMENTALS
 The Building Envelope:
THE FUNDAMENTALS
 Internal Loads:
THE FUNDAMENTALS
 Inefficiencies:
 About 15%-20% of Energy Savings could be achieved in
Commercial Buildings if
Equipment Inefficiencies could be eliminated
 System Configuration Improvements
 System and Sub-System Operations could be optimized
 Whole-Building system control and operation algorithms could be
implemented
 And with some (even minor) attention to detail in the operation of
mechanical systems
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DESIGN FOR NZEB
 Building Envelope Measures
 Orientation – optimize natural daylighting, passive solar heat
in winter & minimize solar heat gains through fenestrations
 Increase R-values of walls and roof with enhanced envelope
insulation
 External shading devices to minimize direct sunlight in
summer (fins, overhangs, plants)
 Skylights for natural daylighting and monitors to bring
daylight into building core
 Optimize envelope surface performance (reduce glazing areas
in E/W facing surfaces, increase in N/S)
DESIGN FOR NZEB
 Equipment & Lighting Measures
 High-efficiency lighting controlled with occupancy sensors
 Daylighting controls to lower lighting and cooling
requirements
 High-efficiency water heating systems to reduce stand-by
losses
 Maximum use of outside air ventilation when outside
temperatures are low (free cooling)
 Demand controlled ventilation with occupancy sensors
 Ground source heat pump systems for higher COP’s
 Variable speed fans and pumps to reduce energy distribution
energy at part load conditions
DESIGN FOR NZEB
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Waste heat recovery
Evaporative cooling
Internal energy wheeling
Optimized controls
Occupant and operator training
DESIGN FOR NZEB
 Renewable Energy Measures
 Solar thermal collectors for service water as well as space
heating
 Photovoltaic panels for direct electricity generation
 Electricity generation from wind energy
 Geothermal energy utilization
 Biomass
 Other renewable energy technologies as appropriate
AN EXTREME CASE STUDY
 IDeAs Z-Squared Design Facility
 Located in San Jose, CA
 Retrofit of a 1960’s Building
 6,560 sqft, 2-story
 Urban Setting
 Currently Operational
 Z-Squared (net zero energy and net zero carbon emission
AN EXTREME CASE STUDY
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All Electric
30kW Roof-Mounted PV Arrays
Heating and Cooling via GSHP
Heating System is Radiant Hot Water
Cooling System is Air
Significant Lighting Controls via Occupancy Sensors
Daylighting Monitors for Lighting of Building Core
Electrochromic Glass on Fenestrations to Reduce Solar Gains
Sunshades with Integral PV Cells
NZEB
 ASHRAE NZEB Video
CONCLUSIONS
 More to be done!
RESOURCES
 DOE Websites
 EERE: Building Technologies Program Home Page
 NZEB Database
 NZEB Projects
 Building Energy Modeling Software
 Financial Opportunities & Tax Incentives
 ASHRAE
 US Green Building Council
 LEED
 LEED Project Profiles