Zero net energy (ZNE) buildings are designed to use no more energy annually than is provided by renewable energy sources. California legislation requires all new homes and commercial buildings to be ZNE by 2020 to 2030. ZNE buildings emphasize passive solar design principles during construction to maximize energy efficiency and renewable energy generation, such as optimizing south-facing glass, thermal mass, and natural ventilation.

1. Zero Net Energy
LNT/SES 101 – Fall 2017
Mark Valen

2. Zero Net Energy
• A zero‐energy building, aka zero net energy (ZNE), is
a building in which the total amount of energy used by
the building on an annual basis is equal to the amount
of renewable energy created on the site, or by
renewable energy sources elsewhere.
• Most ZNE buildings get 50%+ energy from the grid, and
return it at other times.
• “Energy‐plus buildings"
• “Ultra‐low energy houses".
• Research based: energy performance data and
computer models predict the efficacy of various
designs.

3. Legislation
• State of CA: all new residential and
commercial buildings, designed
and constructed to ZNE standards
by 2020 and 2030.
• Included in California Building Code
(updated every 3 years)
• The California Energy Commission
to perform a cost‐benefit analysis
to determine net benefit for
residents.

4. Design and Construction
• The most cost‐effective steps toward a reduction in
a building's energy consumption usually occur
during the design process.
• Typically prioritizes passive solar design principles.

5. Traditional Housing
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• Wigwam – Eastern Woodlands

6. Traditional Housing
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• Longhouse – 200 feet long, 20 feet wide, and 20
feet high

7. Traditional Housing
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• Tipi – Great Plains

8. Traditional Housing
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• Grass house – Southern Plains

9. Traditional Housing
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• Wattle and Daub – Southeast

10. Traditional Housing
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• Chickee – Florida

11. Traditional Housing
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• Adobe – Southwest

12. Traditional Housing
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• Earthen house – Semi‐Subterranean

13. Traditional Housing
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• Plank house – Northwest

14. Traditional Housing
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• Igloo – Arctic

15. Traditional Housing
• Brush house – Coastal Southwest
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16. Passive Solar Design
• The Passive Solar House ‐ the use of the sun’s energy
for the heating and cooling of living spaces.
• Heating
• South Facing Glass
• Thermal Mass
• Cooling
• Ventilation
• Thermal Chimney
• Wind scoops
16http://www.youtube.com/watch?v=b0GcIK2N17I

17. Passive Solar Design
• South facing glass admits solar energy
into the house
• Thermal mass in the interior absorbs the
sunlight and radiates the heat at night.
• It is also possible to use water containers
inside the house to store heat.
• The thermal mass will temper the
intensity of the heat during the day by
absorbing the heat. At night, the thermal
mass radiates heat into the living space. 17
Direct Gain – the actual living space is a solar collector, heat
absorber and distribution system.

18. Passive Solar Design
• Additional useable space:
Sunroom/Greenhouse
• Have a ventilation system for
summer months.
• If overhead glass is used in a
sunroom, use heat reflecting
glass and or shading systems in
the overhead areas.
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Isolated Gain – Solar collector separate from the main living
area of a house.
https://www.youtube.com/watch?v=N2so9hyNWxc

19. Passive Solar Design
• Passive Cooling ‐ cooling buildings without mechanical
assistance
• Wind Tower
• Solar Chimney
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20. Passive Solar Design
• Wind Tower / Windcatcher ‐ a traditional Persian
architectural element to create natural ventilation in
buildings
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•Downward airflow due to direct
wind entry
•Upward airflow due to temperature
gradient

21. Passive Solar Design
• Solar / Thermal Chimney ‐ a hot zone with an exterior
exhaust outlet that allows cool air to be drawn into the
house.
• Thermal Collector Area
• Could be the chimney itself
• Usually painted black
• Main Ventilation Shaft
• Inlet and Outlet
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22. Daylighting
Daylighting is the practice of placing windows or
other openings and reflective surfaces so that during
the day natural light provides effective
internal lighting.
https://www.youtube.com/watch?v=cQCHvO2H0_0

23. LED Lighting
• An LED lamp is a light‐emitting diode assembled
into light bulb.
• lifespan and electrical efficiency several times greater
than incandescent & fluorescent lamps

24. Alternative Methods/Materials
• Earth‐sheltered
• Straw‐bale Construction
• Vitruvian
https://www.youtube.com/watch?v=drKMkIePBAw

25. Landscaping
• Summer Shade, Winter Windbreaks

26. Energy Harvest vs. Conservation
• ZNE has been criticized as a conventional house
with DG technologies.
• Passive solar design has demonstrated heating energy
consumption reductions of 70% to 90%.
• For new designs/builds, this can be accomplished with
little additional construction cost.
• Very few industry experts have the skills or
experience to fully capture benefits of the passive
design.

27. Occupant Behavior
Studies of identical homes in the United States have
shown dramatic differences in energy use, with some
identical homes using more than twice the energy of
others.
• Programming thermostats
• Varying levels of illumination and hot water
• Amount of electric devices used

28. ZNE Advantages
• Isolation from future energy price increases
• Increased comfort (more‐uniform interior temps)
• Reduced total cost of ownership
• Reduced total net monthly cost of living
• Reduced risk of loss from grid blackouts
• Improved reliability
• Higher resale value

29. ZNE Disadvantages
• Initial costs can be higher
• Few designers or builders have the necessary skills or
experience to build ZNE
• Possible declines in future renewable energy costs may
lessen the value of capital invested
• New PV equipment/technology price has been falling at
roughly 17% per year
• While the individual house may use an average of net
zero energy over a year, it may demand energy at the
time when peak demand for the grid occurs
• Solar energy capture using the house envelope only
works in locations unobstructed from the sun.

30. ZNE vs. Green Building
• ZNE achieves one key green‐building goal: reducing energy
use and ghg emissions.
• ZNE may or may not be considered "green" in all areas.
(reducing waste, recycled materials) Because of the design
challenges and sensitivity to a site that are required to
efficiently meet the energy needs of a building and
occupants with renewable energy (solar, wind, geothermal,
etc.), designers must apply holistic design principles, and
take advantage of the free naturally occurring assets
available, such as passive solar orientation, natural
ventilation, daylighting, thermal mass, and night time
cooling.
Certification
• Green building certification programs do not require ZNE,
only energy reduction.