Frequently Asked Questions
Q1/What is a Zero Net Energy Building?
A zero net energy (ZNE) building produces as much energy as it consumes over the course of a year. These buildings achieve ZNE first through high levels of energy efficiency, and then through the addition of clean, on-site renewable power generation, typically solar PV.
Q2/Are ZNE Buildings Feasible?
Yes. While the market share of ZNE buildings is still extremely small, there are numerous examples around the country, built by a variety of design teams and developers, across many different residential and commercial building types. ZNE projects are located in a variety of U.S. climates. ZNE is relatively easier to achieve in milder coastal climates with lower conditioning needs and therefore lower energy consumption; however, the warmer inland climates can also achieve ZNE through efficiency measure and appropriate sizing of on-site renewable generation.
Q3/What are some benefits of ZNE homes?
ZNE homes are higher performing, more resilient to the impacts of climate change, and less vulnerable to the instability of energy prices. California's homeowners and businesses will tend to pay less for energy— leading to a higher monthly cash flow.
ZNE homes are more comfortable, healthier and will tend to have more value when sold.
Investment in ZNE practices and technologies creates local jobs and new products that can be exported worldwide, strengthens local economies, and helps us gain control of our energy future.
Q4/Why is it important to make homes ZNE?
Energy efficiency improvements in building design and operations substantially reduce the costs and environmental impacts associated with buildings. The energy used in buildings is the second largest contributor to California’s greenhouse gas (GHG) emissions. With rising energy costs, and increasing climate-related impacts and natural disasters, ZNE buildings help reduce our demand for energy and provide more resilience to climate impacts.
Q5/What is California Doing to Advance ZNE homes?
California’s building energy efficiency standards (Title 24) are one of the most progressive in the nation and are constantly moving towards increasing levels of high energy performance in new buildings. To date, California has more buildings that are closer to ZNE, than any other state in the nation. The state is continuing its leadership by:
Setting bold goals to achieve ZNE by 2020 for all new residential buildings and by 2030 for all new commercial (and 50% of existing commercial) structures;
Providing technical assistance and incentives for owners and design teams (e.g. through programs like “California Advanced Homes” (residential) and “Savings by Design” (non-residential);
Demonstrating ZNE leadership in state buildings (per Governor’s Executive Order B-18-12);
Investing in new technologies and research for increased energy efficiency;
Providing incentives for rooftop solar (PV) for new homes that meet the highest efficiency standards, through the New Solar Homes Partnership.
Q6/How do you get to ZNE in a home?
Achieving ZNE requires a combination of energy efficiency and renewable energy production. Designing for high energy performance is the first step and requires establishing a goal at the beginning of the project and working under an “Integrated Design Process.” A home must:
Reduce the amount of energy a home uses through the most efficient envelope design strategies, daylighting, as appropriate, and application of highly energy-efficient technologies including lighting, HVAC, and controls.
Optimize the way the building actually operates and how people use it, including management of plugged-in devices and system controls.
Install renewable generation on-site to meet the remaining energy needs of the building. Installed renewable resources have been primarily photovoltaic (PV) panels.
Q7/How much more does it cost to build a ZNE home?
Recent studies have indicated that the efficiency components of a new ZNE home have an incremental cost, after incentives, of just $2-$8 per square foot. (California Zero Net Buildings Energy Cost Study, Davis Energy Group, Inc., PG&E, 2012) Custom home builders who are developing ZNE homes right now indicate that there are nominal additional costs and that the key issue to achieve ZNE is design and quality construction.
Q8/How Efficient Are Typical ZNE Or ZNE-Capable Buildings?
Energy efficiency should be the first and largest step towards ZNE. These buildings should use two-thirds or less of the energy of a typical existing home. Both ZNE and ZNE-Capable buildings should meet Energy Use Intensity (EUI) scores of the highest performing buildings for a given climate zone and building type, for both gas and electric use.
Q9/Does ZNE = A Zero Energy Utility Bill?
Not necessarily. The “net” in zero net energy means that sometimes a building will put back energy into the grid when the building is generating more energy than it is using. A ZNE building's performance will be measured over the course of the year and will be impacted by occupant behavior as a factor to achieve the highest savings. Therefore, due to seasonal changes and use patterns utility bills will not be zero.
Q10/How Do I Know If My Building Has Achieved ZNE Performance?
Metering data will definitely tell a building owner if the building has met a ZNE standard– both energy used by the building and generated by the renewable resources. Because ZNE buildings achieve this status over the course of a year, data at full occupancy for 12 consecutive months is required to verify net-zero energy performance. Plugged-in devices, proper management of controls and occupant behavior have a significant and ongoing impact on a building’s energy performance. This means that buildings designed to be ZNE may not be designated ZNE for some time after the doors are officially opened.
Q11/How can I get involved with planning for ZNE homes in California?
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and provide you information about participating in future meetings and events.
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