This document summarizes a presentation about building towards net zero energy homes. It discusses the NAHB Research Center's work promoting energy efficient housing technologies through research partnerships. It provides an overview of zero energy home basics, including making the home highly efficient and using renewable energy systems to offset overall energy usage. The document concludes with a case study of a net zero energy home built in the Armory Park del Sol community in Tucson, Arizona, and lessons learned from monitoring its energy performance over one year.

1. Building Towards Net
Zero
Amber Wood
Manager, Energy Programs
NAHB Leading Suppliers Council
June 7, 2012
Driving Innovation in Housing Technology

2. NAHB Research Center
Upper Marlboro, MD
 Housing R&D and laboratory testing
 Promote innovation
 Enhancing quality & affordability
 Promoting high standards for the
building industry
2

3. 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

4. 4

5. Why ZEH? 5

6. What is ZEH?
Efficient Efficient Renewable
Envelope Equipment energy
systems
Annually producing as much
energy as consumed

7. Types of ZEH
Builder-Installed Electric nZEH
Production Accounts for All Builder-
Installed End-Uses
All Electric nZEH
Production Accounts for All Electric
Total House nZEH
Production Accounts for All Electric +
Excess to Account for Other Fuels
Net Producing House
Produce > Consume
7

8. ZEH Disclaimer
 A Zero Energy Home is NOT:
 Zero energy consumption
 Utility independent
 Energy rationed
 Energy unlimited
8

9. The Basics
Hathaway
home, Purcellville
, VA. NREL photo
archive
1. Decrease total energy use
2. Produce energy from renewable sources
9

10. An Energy Efficient Home
House Shell: Water Heating:
Added insulation, low-e Solar
windows, insulated preheat, efficient
foundation, overhangs, delivery, low-flow
orientation fixtures
Lighting:
Fluorescent fixtures/
Air-sealing: bulbs, daylighting
Seal vents, holes and
gaps through walls and
roof Appliances:
ENERGY STAR®
Label
Heating & Cooling
Equipment: Plug Loads &
High Appliances:
Efficiency, programma Homeowner’s
ble thermostat, sealed choice to decrease
ducts, ventilation use
10

11. Effect of Efficiency
Upgrades
12,000 120%
110%
10,000 100%
Annual Consumption (kWh)
90%
Percent Reduction in Use
8,000 80%
70%
6,000 60%
50%
4,000 40%
30%
2,000 20%
10%
0 0%
Heating Cooling Water Heating Ventilation Air All Other Loads
Primary Energy Category
Base House Net-Zero Design Reduction in Use
11

12. Example ZEH Energy Use
Baltimore, MD
Base House
Percent Net-Zero Annual
Annual Percent of
Energy End Use of Consumption
Consumption Total (%)
Total (%) (kWh)
(kWh)
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
 PV System
 5,700 W
 500 sqft area
 Produce 8,266 kWh 12

13. ZEH Approaches
ZEH
Details Involving
Builder, Trades, Gover
nment, etc.
13

14. Current ZEH Experience
 Over 50% minimum reduction in
total energy
 Typically 50 – 70%
 Net-zero electric bill
 Gas offset unavailable
14

15. Solar Water Heating System
15

16. Solar Electric (PV) Systems
 Convert sun energy
to electricity
 Operate daily
 Output varies
 PV Systems are ZEH remodel in NJ, courtesy of Bill Asdal
 Available,
 Reliable, &
 Low maintenance
 Quiet
16

17. Utility Connection
17

18. 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
18

19. Armory Park del Sol
A Historic Solar Community
John Wesley Miller Companies
&
NAHB Research Center

20. Armory Park del
Sol
 Urban in-fill
 Southern Pacific RR executive
homes
 Existing infrastructure
 Downtown Tucson
 Rio Nuevo Project
 Walking distance to downtown &
university
 Cultural activities, arts, & music

21. Armory Park del
Sol

22. 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
 Neighborhood embraced
project
 Increased local property
values

23. Armory Park del
Sol
 Single family homes
 New technology/
construction methods
 Southwestern design
 Concrete construction
 Thermal mass
 Metal framing
 Termite-proof
 Significant energy
savings

24. Armory Park del
Sol
 Energy efficiency construction
 Thermal mass
 Exterior insulation
 Insulation through slab edge
 Raised heel truss, R-38 ceiling
 Dual-pane, Low-E & Low SHGC
windows
 Ducts in conditioned space
 14 SEER heat pump
 HVAC system design with Manual J
 Optimized (reduced) duct runs
 Return air pathway from each room
 Passive ventilation system

25. 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

26. Armory Park del
Sol
 Solar System Attributes
 One solar subcontractor (The Solar Store)
 Subsystems & components from major manufacturers
 BP PV Modules
 Trace Inverters
 Meets TEP SunShare requirements (ACC approved)
 Compliance
 IEEE
 National Electric Code
 TEP Service Requirements Book

27. 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

28. 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

29. 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

31. 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

32. Armory Park del
Sol
 APdS Standard Homes
 Predicted to use less than half the energy of a
typical regional home

33. John Wesley Miller Companies’
Net Zero Energy Home Project

34. Zero Energy Home
Construction
34

35. 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
3

36. Zero Energy Home Design
Team
NAHB Research Center, Inc.
Project Management
Design Support
Monitoring Armory Park Del Sol
Project Summary Build
Information Dissemination Define Constraints
Consumer Education
Consumer
Information
Feedback
Solar Store Manufacturers
Design Design Support
Manufacturer Contact Product Specification
Solar Components Installation Requirements

37. Zero Energy Home
Construction 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
37

38. Masonry Walls

39. 2” Polystyrene

40. Radiant Roof Decking

41. Window & Porch Overhangs

42. Air Admittance Valves

43. Systems in Conditioned
Space

44. 4 kW PV System

45. 45

46. John Wesley Miller Companies’
Zero Energy Home (ZEH)
 Now averaging about $10/mo (including $5.28
monthly base fee)
 Average 23 kWh/day Total Average Energy Use
Tucson ZEH at Armory Park del Sol
Monthly Total Energy Use and Cost
1,800 $90
Modifications to solar thermal system
1,600
(+ values = House Use; - Values = Utility Feedback) complete $80
Electric Energy, kWh; Solar Insolation, kWh/m 2
1,400 $70
1,200 $60
Monthly Energy Cost
1,000 $50
800 $40
600 $30
400 $20
200 $10
0 $0
-200 -$10
Values less than zero indicate sell-back to the utility
-400 -$20
Apr-04
Apr-05
Apr-06
Aug-04
Aug-05
Aug-06
Oct-03
Dec-03
Jul-04
Sep-04
Dec-05
Jan-04
Feb-04
Jun-04
Oct-04
Dec-04
Jan-05
Feb-05
Jun-05
Jul-05
Sep-05
Oct-05
Jan-06
Feb-06
Jun-06
Jul-06
May-04
May-05
May-06
Nov-03
Nov-04
Nov-05
Mar-04
Mar-05
Mar-06
Energy Cost Utility Supply PV Supply PV Insolation

47. ZEH End Uses
Tucson ZEH
Data from 9/1/05 to 8/31/06
A/C Compressor, kWh,
1,847
Other, kWh, 3,536
Utility
Supply,
kWh,
1158,
Blower, kWh, 663 14%
PV
Supply,
kWh,
7209,
86%
Demand Water Heater,
kWh, 1,040
Refrigerator, kWh, 631
Lights, kWh, 651

48. ZEH 1st Year Monitoring

49. ZEH Occupied
Period Monitoring

50. ZEH Monitoring Results

51. Year 1 ZEH Monitoring
Results

52. ZEH Monitoring Results
Inverter-Demand Heater
Compatibility

53. ZEH Monitoring Results
PV System Output

54. Plug Loads
The big
challenge…
54

55. Energy Simulation
Summary
Annual Electrical Consumption
Description 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 55

56. ZEH 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 56

57. ZEH 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
57

58. ZEH Lessons Learned
 PEX plumbing
 Design is important
 Different installation
method
 Lighting
 Whole-house permanent
fluorescent lighting options
NOT mainstream
 New technologies emerging
(LED, etc)
 Plug loads still need control 58

59. John Wesley Miller Companies’
Zero Energy Home 2 (ZEH2)
 ZEH2 Utility Savings Estimate
 PV system cost benefit offsets utility-supplied energy

60. ZEH2 Energy Features
Tucson, AZ
 Concrete Block Construction
 Foundation
 12” floating slab
 Exterior Insulation
 2” exterior insulation (R-13)
 Attached using z-strips
 Ceiling & Roof Insulation
 R-38 ceiling insulation
 1” rigid foam on roof deck (R-6.5)

61. ZEH2 Energy Features
(cont.)
 High Efficiency Space
Heating and Cooling
 Heat Pump: Trane XL19i
 Two-stage compressor
 Variable speed blower
 Sealed ducts in conditioned
space (22 CFM25 – total)
 Mechanical Ventilation
 Mechanical room exhaust fan
 Fresh air to central return

62. ZEH2 Energy Features
(cont.)
 Solar Hot Water
Preheat System
 Closed loop
 80G storage
 64sf collector
 Tankless Backup
Water Heater
 Manifold
Distribution
System

63. ZEH2 Energy Features
(cont.)
 Efficient Windows
 U-value: 0.35, SHGC: 0.30
 Air Sealing Package
 740 CFM50
 Lighting
 90% Hard-wired fluorescent lighting
 ENERGY STAR fixtures
 CFL
 Appliances
 ENERGY STAR
Refrigerator, Dishwasher, Washing
Machine

64. ZEH2 Energy Features
(cont.)
 Solar Electric PV
System
 6.93 kW (DC) PV
System
 Net Metered
 > 100%
Predicted
Energy Savings
with PV

65. Code Approval & Programs
 Meets all safety, health, and 2006
IBC & 2006 IECC code requirements
 Tucson Electric Power’s (TEP’s)
Guarantee program
 5 year heating/cooling & comfort
 Tucson Sustainable Energy
Standard
 Performs 50% better than the Model
Energy Code
 Builders Challenge
 Builder Federal Tax Credit
 Local & State Tax Incentives

66. Quality Control Requirements
High Performance Home Specifications
 Envelope Moisture Control
Foundation drainage/capillary breaks – n/a slab design
Climate appropriate vapor retarder – n/a due to climate &
masonry wall construction
Continuous drainage plane – felt paper over fixed
polyisocyanurate
 Envelope Air Tightness
740 CFM50
 Space Conditioning
Equipment and duct sizing per ACCA methodology

67. Quality Control Requirements
High Performance Home Specifications
 Space Conditioning (cont.)
Distributed whole house mechanical ventilation – exhaust fan
and a central fan integrated supply
Local exhaust – bathrooms, kitchen
Filtration – Honeywell electronic air cleaner
Sealed ducts in conditioned space
No combustion appliances or fireplace
System capable of maintaining RH < 60%
 Hot Water
SRCC rated collectors for solar hot water system

69. Neutral Cost Target
Upgrade Costs

70. Neutral Cost Target
Efficiency Feature Upgrades
Note: PV not included

71. Neutral Cost Target
Tax Credits & Incentives

72. Neutral Cost Target
Efficiency Feature Upgrades w/ PV
Note: PV incentives not included for Std Home

73. Neutral Cost Target
Efficiency Feature Upgrades w/ PV
Note: PV incentives included for Std Home

74. Value of ZEH
74

75. ZEH2 Conclusions
 APdS demonstrates increasing
levels of energy efficiency
 ZEH is possible
 Technologies “off-the-shelf,”
 Attention to builder’s marketing
effort is necessary
 Builders Challenge
 Green Building
 Local Utility Programs

76. Whole House Energy
ZEH1 Monitoring
Comparison – ZEH

77. Whole House Energy
ZEH2 Monitoring
Comparison – ZEH2

78. Incentives
78

79. Federal Incentives
 Tax Credit:
 30% of cost with no upper limit
 Expires:
 December 31, 2016
 Details:
 Existing homes & new construction
 Principal residences & second homes
 Rentals do not qualify
79
NEXUS EnergyHomes

80. Incentive Details
 Solar Water Heat
 Certified by SRCC or equivalent a
 Must provide ≥ 50% dwelling’s water heating
 Not apply to swimming pools/hot tub
 Photovoltaics
 Wind
 Fuel Cells
 $500 per 0.5 kW maximum
 Geothermal Heat Pumps
 Meet federal Energy Star criteria 80

81. Solar Renewable Energy
Certificates (SRECs)
 In SREC states, Renewable Portfolio
Standard (RPS) requires some electricity
from solar
 The SREC program provides a means for
SRECs to be created for every megawatt-
hour of solar electricity created.
 1 SREC = 1,000 kWh of solar electricity = 1
MWh of solar electricity
 10 kW solar capacity = ~12 SRECs per year
81

82. Maryland SREC Market
 Energy Year
 Jan 1 - Dec 31
 SREC Useful Life
 3 years
 Solar Requirement
 Reaching 2% of total elec generated in 2021
 Solar Alternative Compliance Payment
(SACP)
 $400 through 2014
82

83. 83

84. Summary
 ZEH used to be all about cost
 Still an interest in ZEH, driven by
 Increasing utility costs
 Lower cost of PV
 Familiarity (owners & trades)
 Consumer acceptance
 Utility acceptance
 New financing mechanisms
 Changing accessibility
84

85. Programs
 Energy Efficiency Certification
 ENERGY STAR
 DOE Challenge Home
 Energy Efficiency Research & Development
 Building America Program
 Green Certification
 National Green Building Certification Program
 Awards 85

86. References
 NAHB Research Center Technical Website
 www.toolbase.org
 DOE Energy Information Administration (EIA)
 www.eia.gov
 DOE/EERE Buildings Energy Data Book
 http://buildingsdatabook.eren.doe.gov/default.aspx
 ENERGY STAR
 www.energystar.gov
 Database of State Incentives for Renewables
& Efficiency (DSIRE)
 www.dsireusa.org
86

87. Questions?
87

88. 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
Driving Innovation in Housing Technology