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4. Practical Categorization of “Zero-Energy” Projects
The Net-Zero Energy Coalition (NZEC), a private, non-profit organization dedicated to the fa- cilitation of knowledge transfer about ZNE buildings, defines a zero-energy project as simply one that produces as much renewable energy as it consumes in a year5. NZEC categorizes ZNE residential projects as one of three types: “Net Producer”, “Zero Energy” or “Zero-Energy Ready”. These types of ZNE projects are defined as follows:
A “Net Producer” project has an on-site renewable energy system that supplies 110% or more of its annual energy use. (“Net Positive” is another term sometimes used to describe the same type of performance.) A “Zero Energy” project has a renewable energy system that supplies 100% to 110% of its annual energy use. Alternatively, the project can be certified as ZNE by the third party organizations, International Living Futures Institute or the Thousand Home Challenge to qualify for the “Zero Energy” label by NZEC.
The third category, “Zero-Energy Ready” 6, is a deliberately broad category to be as inclusive as possible of projects that don’t quite meet the standards of the first two categories. These include projects which:
• Have a renewable energy system that supplies 90% or more of its annual energy use;
• Will be able to meet the requirements of the “Zero Energy” category if/when sufficient renewable energy capacity is added;
• Are designed to meet the requirements of the “Zero Energy” category, but no documenta- tion is available (one possible example: because the project has not yet been in operation for a year);
5 Net Zero Energy Coalition, “To Zero and Beyond”, (April, 2018), p. 10.
6 The NZEC “Zero-Energy Ready” category is not exactly the same as the federal performance category of the same name since more specific energy-efficiency measures are prescribed
for the federal label. However, a “Zero-Energy Ready” home in the federal definition would automatically qualify for NZEC category.
INTRODUCTION
ZERO NET ENERGY CASE STUDY HOMES
(Left) The HERS Index as “aligned with” the California Energy Design Rating (EDR), the rating system for residential projects as established by the California Energy Commission and as calculated using certi- fied energy modeling software based on the TDV metric.
Zero Net Energy Case Study Homes: Volume 1
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