Driving Innovation in Housing Technology

Net Zero Energy Case Study

Amber Wood

Manager, Energy Programs

EEBA Conference 2011

September 16, 2011

2

NAHB Research CenterUpper Marlboro, MD

Housing R&D and laboratory testing Promote innovation Enhancing quality & affordability Promoting high standards for the

building industry

Building America

Private/public R&D partnership sponsored by DOE

Energy-efficient solutions for new and existing housing Technologies/Systems Whole-House Test Homes Quality Processes

4Mar

ylan

d Z

EH

Pro

ject

Why ZEH?

What is ZEH?

Efficient Envelope

Renewable energy

systems

Efficient Equipment

Annually producing as much energy as consumed

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ZEH Disclaimer

A Zero Energy Home is NOT:

Zero energy consumption Utility independent Energy rationed Energy unlimited

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The Basics

1. Decrease total energy use

2. Produce energy from renewable sources

Hathaway home, Purcellville, VA. NREL photo archive

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An Energy Efficient Home

House Shell:More wall and roof insulation, low-e windows, insulated foundation, overhangs, passive solar orientation

Heating & Cooling Equipment:High Efficiency, programmable thermostat, sealed ducts, ventilation

Water Heating: Solar preheat, efficient delivery, low-flow fixtures

Appliances: ENERGY STAR® Label

Lighting:Fluorescent, daylighting

Plug & Small Appliances:Individual homeowner’s choice to decrease use

Air-sealing:Seal vents, holes and gaps through walls and roof

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Effect of Efficiency Upgrades

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2,000

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6,000

8,000

10,000

12,000

Heating Cooling Water Heating Ventilation Air All Other Loads

Primary Energy Category

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Base House Net-Zero Design Reduction in Use

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Example ZEH Energy UseBaltimore, MD

PV System 5,700 W 500 sqft area Produce 8,266 kWh

Energy End Use

Base House Annual

Consumption (kWh)

Percent of

Total (%)

Net-Zero Annual Consumption

(kWh)

Percent of Total (%)

Heating 12,749 47 2,110 26

Cooling 5,100 19 850 11

Water Heating 3,627 13 167 2

Ventilation Air 0 0 175 2

All Other Loads 5,730 21 4,833 59

Annual Consumption 27,206 100 8,135 100

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ZEH Approaches

ZEH

Details Involving Builder, Trades, Government, etc.

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Current ZEH Experience

Over 50% minimum reduction in total energy Typically 50 – 70%

Net-zero electric bill Gas offset unavailable

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Solar Water Heating System

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Solar Electric (PV) Systems

Convert sun energy to electricity Operate daily Output varies

PV Systems are Available, Reliable, & Low maintenance Quiet

ZEH remodel in NJ, courtesy of Bill Asdal

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Utility Connection

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ZEH Utility Requirements

Utility must “net-meter”: credit for electricity fed back to the utility

Utility must “settle” credit not less than once a year

Utility must be ON to have PV power

Armory Park del SolA Historic Solar Community

John Wesley Miller CompaniesAnd

NAHB Research Center

Armory Park del Sol

Urban in-fill Former site of Southern Pacific RR executive

homes Utilization of existing infrastructure

Downtown Tucson Rio Nuevo Project Walking distance – downtown & University of

Arizona Cultural activities, arts & music

Tucson Convention Center Theatre, Symphony, concerts Artist galleries Museums

14 acre subdivision

Urban in-fill in downtown Tucson

Single family homes

Awards for energy efficiency construction

Utility collaboration

Armory Park del Sol

Armory Park del Sol

14 acre subdivision Purchased land in 1999 99 lots Construction started 2000

Historic Armory Park/ Armory Park del Sol

Designs blend with area tradition

Neighborhood has embraced project

Local property values much higher

Armory Park del Sol

Single family homes New technology/

construction methods Traditional Southwestern

exterior design Metal framing

Termite-proof

Concrete construction Thermal mass

Significant energy savings

Armory Park del Sol

Energy efficiency construction Thermal mass wall – exterior insulation Insulation through slab edge Raised heel truss, R-38 ceiling Dual-pane, Low E & Low Solar Heat Gain

windows Ducts in conditioned space 14 SEER heat pump HVAC system design using Manual J Optimized (reduced) duct runs Return air pathway from each room Passive ventilation system

Armory Park del Sol

Solar Electric Technology 1.5 kW Photovoltaic (PV) system minimum Garage roof mount (parapet wall) Utility approved components & systems; annual

utility inspection

Armory Park del Sol

Solar System Attributes One Subcontractor (The Solar Store) installed all systems Subsystems & components from major U.S. or multi-national firms

BP PV Modules Trace Inverters

System meets TEP SunShare requirements (ACC approved) Compliance

IEEE National Electric Code TEP Service Requirements Book

Armory Park del Sol

Single family homes Information age design

Minimum 3 telecom ports Digital Satellite Service CAT5e wiring Pre-wired for fiber optics

Security system Central vacuum

Armory Park del Sol

Utility collaboration Tucson Electric Power 5 year A/C guarantee

TEP inspects each home during construction Guarantee qualifies Armory Park del Sol for

reduced residential utility rates Guarantees heating & cooling portion of annual bill

Armory Park del Sol

Utility Collaboration / Solar

Electric System State & federal tax credits Homeowner qualifies for TEP cash rebates Output offsets highest Time-of-Use rate TEP inspects solar electric system annually City permit fee credit up to $1,000

Armory Park del Sol

Armory Park del Sol

Armory Park del Sol

Solar Energy Homes in Downtown Tucson

An Award Winning Community!

SAHBA Builder of the Year, 2003

City of Tucson Most Energy Efficient Builder, 2003

Sonoran Institute Livable Community Award, 2005

NAHB Builder of the Year Award Winner, 2005

Metropolitan Pima Alliance Common Ground Award, 2006

Armory Park del Sol

APdS Standard Homes Predicted to use less than half the energy of a typical regional home

Armory Park del Sol

Net Zero Energy Home Project

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Tucson Zero Energy HomeConstruction

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Zero Energy Home at APdS

Natural extension of work at APdS

Engineering work funded by DOE through NREL

Goal of net-zero annual energy use

Started with clean sheet of paper

Zero Energy Home Design Team

NAHB Research Center, Inc.Project Management

Design SupportMonitoring

Project SummaryInformation Dissemination

Armory Park Del SolBuild

Define ConstraintsConsumer Education

Solar StoreDesign

Manufacturer ContactSolar Components

ManufacturersDesign Support

Product SpecificationInstallation Requirements

ConsumerInformationFeedback

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Zero Energy HomeConstruction Features

Concrete walls with 2” polyiso R-41 attic U-0.32, SHGC-0.35 windows SEER 18 AC Combined solar (128 sf) space and water

heating system with tankless backup 4.2 kW PV array PEX piping (with some copper) Fluorescent lighting throughout Outdoor living spaces Ceiling fans without light kits Energy Star appliances

Masonry Walls

2” Polystyrene

Radiant Roof Decking

Window & Porch Overhangs

Air Admittance Valves

Systems in Conditioned Space

4 kW PV System

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Tucson ZEH at Armory Park del SolMonthly Total Energy Use and Cost

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Ele

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kW

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So

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Inso

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, kW

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(+

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use

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; -

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ues

= U

tilit

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-$20

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Energy Cost Utility Supply PV Supply PV Insolation

Values less than zero indicate sell-back to the utility

Modifications to solar thermal system complete

Zero Energy Home 1 Now averaging about $10/mo (including $5.28 monthly base fee) Average 23 kWh/day Total Average Energy Use

Armory Park del Sol

Blower, kWh, 663

A/C Compressor, kWh, 1,847

Demand Water Heater, kWh, 1,040

Other, kWh, 3,536

Refrigerator, kWh, 631

Lights, kWh, 651

Data from 9/1/05 to 8/31/06

Utility Supply,

kWh, 1158, 14%

PV Supply,

kWh, 7209, 86%

Tucson ZEH

ZEH 1st Year Monitoring

ZEH Occupied Period Monitoring

ZEH Monitoring Results

Year 1 ZEH Monitoring Results

ZEH Monitoring ResultsElectric Demand

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ZEH Monitoring ResultsElectric Demand(w/o Dmd. Heat)

ZEH Monitoring ResultsCooling Stage Operation

5° Decrease in T’stat setpoint

10° Rise in average ambient T

1.86 kWh/day to 17.3 kWh/day

ZEH Monitoring ResultsSolar Thermal - Losses

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Solar Thermal System

• 210 gallon non-pressurized storage tank

• 18 kW demand heater

• 128 sf collector area

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Solar Thermal Heating Summary

Table 1. Summary of Daily Solar Thermal System Performance

Average Min Max Insolation on Solar Thermal Array, kWh/day

6.15 0.63 8.38

Storage Tank Temperature, deg F 129.5 94.1 159.9 Hot Water Usage, gallons per day 62.4 33.8 122.8 Domestic Hot Water Energy Use, Btu/day

23,750 10,858 46,572

Solar Thermal Collector Production (Btu/day)

56,400 0.0 104,000

Solar Thermal Collector Efficiency (days > 5,000 Btu production)

22.8% 6.0% 35.2%

The solar thermal system did not perform as expected. The average thermal energy collected during the heating season was much lower than the anticipated 80,000 to 90,000 Btu/day. If the system had performed as anticipated, the average daily heating and water heating load of 70,800 Btu/day could easily have been met by solar energy. Further investigation is needed to determine why the collector system is not performing as designed.

3rd Quarterly Report

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Solar Thermal Heating Summary

3rd Quarterly Report

Table 1. Summary of ZEH Heating Season Performance

Measured Results Simulated Results Heating Period (November 1 – March 31) 151 days* HDD (November – March) 1,084 1,412 Ambient Temperature (average) 58.1 °F 55.3 °F Average Daily Minimum Temperature, °F 44 °F 42 °F Average Indoor Air Temperature** 73.6 °F 73.3 Indoor Thermostat Set Point, °F 72 72 Heating Energy Used, million Btu 7.105 4.637 Domestic Hot Water Energy Use, million Btu 3.586 Solar Energy Collected, million Btu 8.512 Demand Water Heater Supply, million Btu 6.257 System Losses, million Btu 4.079 Proportion of Heating Energy Supplied by Solar 60% Daily Average Heating Energy Use, Btu/day 47,050 30,700 Daily Average Thermal Load (heat and DHW), Btu/day 70,800 Average Daily Solar Energy Collected, Btu/day 56,370 (80,000-90,000 per

design specs) *excluding 1 day of cooling (12/6); **Average at Thermostat

ZEH Monitoring ResultsHot Water Storage - Summer

ZEH Monitoring ResultsHot Water Storage - Winter

ZEH Monitoring ResultsInverter-Demand Heater

Compatibility

ZEH Monitoring ResultsThermal Energy Supply/Use

ZEH Monitoring ResultsThermal Energy Supply/Use

ZEH Monitoring ResultsPV System Comparison

ZEH Monitoring ResultsPV System Output

ZEH Monitoring Results1st Year PV System Output

PV system output = 7323 kWh (32°, 0° azimuth)

Solar Input = 2370 kWh/m2 (6.49 sun-hours/day)

Average AC Array Size = 3100 W

TEP PTC rating for BP4200 dc = 3112 W

TEP Average Annual Supply = 6300 kWh (17.3 kWh/day)

Running Annual Average = 19.5 kWh/day

ZEH Monitoring ResultsThermal System Output

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Plug Loads

The big challenge…

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Energy Simulation Summary

Description

Annual Electrical Consumption

Cooling Heating Fan DHW Lighting Appl/Othr Total

(kWh/yr) (kWh/yr) (kWh/yr) (kWh/yr) (kWh/yr) (kWh/yr) (kWh/yr)

JWM Standard * 3,568 621 772 1,855 1,873 3,687 12,376

ZEH As-Built ** 2,207 200 430 158 779 3,072 6,846

Tucson Standard*** 6,770 669 1,229 4,064 1,873 3,687 18,292

*(includes passive SDHW)**(Option A+B+C+D+E w/ R41 ceiling instead of R43)***Light Frame, R19 ceiling, 10 SEER, double pane wood frame windows

Occupied Use To Date :

Demand Heater = 1,918 kWh, Lighting = 640 kWh, Other = 3,116 kWh

Total Use to Date = 6,406 kWh (26.3 kWh/day)

Estimated Daily = 18.8 kWh

Lighting Energy

Heating season lighting energy 2.4 kWh/day average 1.4 - 5.6 kWh/day range

Simulation lighting estimates Interior 0.13 w/ft2 Exterior 0.04 w/ft2

Average winter lighting energy use 0.06 w/ft2 for both

Annual DOE estimated residential lighting use 1444 kWh average 164 watts average

Tucson ZEH design 100 watts average

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Tucson Lessons Learned

Project Success, Builder interest PV system

Utility interest prime Knowledgeable installer Inverter compatibility problems (new)

Solar Aesthetics Even with flat roofs

Solar thermal system performance Temperature limitations Controller Losses

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Tucson Lessons Learned

Integration of HVAC & thermal system Simple design/connections

Space and access for thermal storage Thermal mass

Winter penalties? Air admittance valves

Manufacturer design required Plumber reticence Work

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Tucson Lessons Learned

PEX plumbing Plastic material questioned Negative history Different installation method

Lighting Whole-house permanent fluorescent

lighting options NOT mainstream Cost is very high

Plug loads

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Recommendations

Continued monitoring Solar thermal system design Thermal mass analysis Resolve inverter/heater compatibility Design for additional ZEH at Armory Park Integration of mechanical systems in

conditioned space

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Recommendations Develop homeowner information Identify values of ZEH Utility flat-rate billing (TOU better) Identify Repeatability

Would this house be built again???

Continue On With ZEH

Zero Energy Home 2 - Utility Savings PV system cost benefit offsets utility-supplied energy

Armory Park del Sol

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Questions?

Driving Innovation in Housing Technology

Thank You!

Amber Wood

NAHB Research Center

Manager, Energy Programs

400 Prince George’s Blvd Upper Marlboro, MD 20774(direct) 301.430.6309 (fax) 301.430.6180

www.nahbrc.com