Spotlight on Net Zero Energy Codes and Standards

Spotlight on Net Zero Energy Codes and Standards

By Jim Meyers, Director of the Building Efficiency Program, Southwest Energy Efficiency Project (SWEEP)

Net Zero Energy Codes and Standards—are they the next step in the code development cycle? It appears so if you look at what the City of Tucson and its county, Pima County, have developed over the past two years in Arizona.  Recently released by both municipalities is the “Net Zero Energy Standard,” an optional compliance path for builders of new residential and commercial buildings.

In many areas of the country just getting compliance with the energy code already on the books is a challenge. But for Pima/Tucson, the next step is to help the fledgling beyond- code builders understand how to build cost-effective net-zero energy homes.

Typically the revolutionaries of highly efficient buildings come from industries of architects, visionary home builders, efficiency advocates, and efficiency product manufacturers. They wear the champion hat and move about the industry promoting the benefits of these building practices.  Radical change is not usually championed by building officials, and in many cases it’s too hard for builders in a conservative industry to create change when they must support the building and its occupants after the sale.  But also in a revolution there is often more than one person who wears the mantle of change agent. In the case of these southern Arizona municipalities official’s worked with industry, academia, and others to bring about this next level of energy efficiency code.

The southern Arizona standard incorporates four important concepts in building these highly efficient homes:

  1. Develop an Energy Use Intensity (EUI) rating for each building which could be analogous to an MPG rating for vehicles.
  2. Offset the energy required to deliver water to the building.
  3. An energy-efficient building with adequate on-site renewable energy generation capability (typically building roof area and orientation).
  4. Outcome- based compliance where the building receives a net-zero energy certificate after one year of operation demonstrates net-zero achievement.  However, meeting the requirements in either the prescriptive or performance paths shall be deemed to be in compliance with the 2012 IECC, without regard to the issuance of a net-zero certificate.

The Net-Zero Energy Building Standard was developed by the City of Tucson and Pima County Development Services, with assistance from the University of Arizona College of Architecture and Landscape Architecture and Tucson Water.  The standard is based upon the recently released and highly energy-efficient 2012 International Energy Conservation Code (IECC).

The team developed two calculators, available at the net-zero energy standard website, the Energy Budget Calculator and the NegaWatt Calculator.  The Energy Budget Calculator is for use by builders who are following the prescriptive requirements of the standard, while the NegaWatt Calculator provides cost and savings calculations to determine the “tipping point,” as Pima/Tucson describes it, to become cash flow positive.  This is the point at which construction cost increases are offset by monthly energy savings from a code built home. The tipping point helps the builder know when it’s time to shift from building efficiency improvements, which are typically less costly, and start installing photovoltaic panels.

The Nega-watt calculator will provide the cost and savings for ‘Nega-watts’ and ‘PV watts’ and assist in determining the “tipping point” and whether or not the project will be cash flow positive. Energy efficiency improvements are generally more cost-effective than installing renewable energy like photovoltaic (PV) panels and solar thermal systems—up to the point when energy production costs become more cost-effective than continued improvements to efficiency in the building. The calculator assists the builder with determining when the cost of energy saved by efficiency improvements, a nega-watt, is more than the cost of electricity produced by PV. This is the “tipping point” when it makes sense to stop making the building more efficient and install PV.

The standard helps the builder and designer by providing a prescriptive path which describes details that will assist the builder and designer in the development of the home. The net zero energy building includes increased envelope requirements, tighter building infiltration, and goes further by defining (orientation attributes, vertical window sizes, and overhangs.

For a peek at what we hope to see in upcoming houses and commercial buildings in southern Arizona visit the net-zero energy standard website.

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