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  • Net-Zero Energy Building Standard

    Net-Zero Energy Building Standard

    What is Net-Zero Energy

    Net-Zero Project

    Net-Zero Energy is when a home or building makes as much energy as it needs to keep you comfortable and save you money!

    Whether you are a homeowner, home builder, commercial builder or commercial property owner, you will find helpful tools and information here to help you build or renovate a net–zero building so you can be cash flow positive on day one cash flow positive tooltip and secure your energy future.

    Zero Energy Buildings: A Critical Look at the Definition


    Energy Budget Calculator for Net-Zero Building Projects

    The Energy Budget Calculator is an application that enables the user of the prescriptive path of the standard to determine their Energy Budget based on selected criteria. A recipe of sorts is shown of the standard required building strategies that need to be incorporated into your net zero building.


    NegaWatt Calculator

    The Nega-watt calculator will provide the cost and savings for Nega-watts and PV watts and assist in determining the "tipping point". Energy efficiency improvements are generally more cost effective than installing photovoltaic (PV) panels, up to a point. This calculator will assist in 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. This tool does not tell you which energy efficiency improvements to make. Use the Net-Zero Energy Building standard for prescriptive path or energy modeling to determine this.

    About the Net-Zero Energy Building Standard

    The Net-Zero Energy Building Standard project was sponsored by the City of Tucson Office of Conservation and Sustainable Development. Pima County Development Services, Building Safety and Sustainability was the principle research group with assistance from the University of Arizona College of Architecture and Landscape Architecture and Tucson Water.

    The Net-Zero Energy Standard has a prescriptive residential section and a prescriptive commercial section covering apartments, office and retail. These building types represent approximately 30% of total energy use in the metro area. The Net-Zero Energy Standard also has a performance section for both residential and commercial that will allow buildings that can not use the prescriptive path to achieve a net-zero certification by using energy modeling software (tooltip).

    Community Sponsors and Support

    Other Calculators

    Volumetric Heat Capacity Calculator for Appendix B (xls)

    The following web pages also provide calculators that can help you with sizing and financing solar.
    • Solar OneStop by the City of Tucson and Pima County. Provides a one stop shop for solar in southern Arizona.
    • TEP PV Calculator shows the system size and financial metrics.
    • Solar Estimate.org shows the system size in kW, roof area required and financial metrics.
    • SolOpt roof top solar optimization spreadsheet by the National Renewable Energy Lab. Provides an optimum break out between solar thermal and PV based on your use, provides the system size in kW for PV and area of collectors for solar thermal and financial metrics.
    Building Energy Efficiency
    The following web pages will provide you with additional information on building in energy efficiency.

    Project Summary Report

    Project summary report for the Tucson/Pima County Net-Zero Energy Building Standard Project.

    Conclusions:
    • Nega-watts cost less than the cost of utility purchased power. In many cases nega-watts cost less than the cost of incentivized photovoltaic (PV) power.
    • Cash flow positive: The decrease in monthly utility bills is larger than the increase in monthly amortized cost due to the energy efficiency improvements and PV power resulting in net positive cash flow to the building owner in the residential and apartment prototypes. The office and retail are not cash flow positive due to the high cost of efficient commercial air conditioning (HVAC).
    Recommendations:
    • Provide incentives to jump-start the market: reward early adopters, bridge the small cash flow gap in energy efficiency improvement cash flow. Market the program to create demand for the benefits of net-zero.
    • Close the gap on long term financing. Cash flow positive is dependent on the inclusion of energy efficiency measures and PV into the initial financing for the construction. Existing loan products exist, e.g., EEM and 203(K) loans, but investor banks have been reluctant to purchase these mortgages due to perceived additional risk.
    Read the project summary:

    Economic Report

    A net zero home or apartment is cash flow positive on day one.

    This means that when the building is built with net-zero energy efficiency strategies and PV on the roof and these are included in the original loan, the increase in mortgage cost is less than the decrease in electricity costs:
      For Energy Efficiency For PV Total Savings
    Electricity Bill Decrease: $129 $187 $316
    Monthly mortgage increase: $78 $162 $223
    Monthly Savings: $51 $25 $83
    Every month, this net-zero energy home owner has $83 additional money in their pocket. Read the following report for more information:
    To see different energy savings case studies, visit the Nega-watt calculator.

    Swamp Coolers and Net-Zero Standard

    This report discusses how evaporative coolers, even when considering the embedded energy in water, use 90% less energy than air conditioners while only adding 5.1% additional water use. They can reduce peak energy requirements thereby reducing peak costs to electric companies. Because of the potential to use a cooler as a whole house fan for night time pre-cooling, a cooler can make a cost efficient and effective cooling system for a well insulated, high thermal mass home.

    Green House Gas Emissions Reduction Report

    This report discusses how the Net-Zero Building Energy Standard has the potential to reduce green house gas emissions and can be an implementation strategy for ten of the action measures listed in the City of Tucson, Community Economic Security and Climate Action Analysis report.

    Case Studies

    Residential Case Studies Commercial Case Studies
    Submit Your Case Study

    Complete the following case study form and email to building.sustainability@pima.gov

    Net-Zero Energy Standard Presentation

    Sponsored in part by the City of Tucson

    Green Building SolarOneStop
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    For projects in the jurisdiction of the City of Tucson

    Clayton Trevillyan
    Chief Building Official

    City of Tucson Planning and Development Services

    (520) 837-4937

    Department Directory
    Department Feedback Form

    For projects in the jurisdiction of Pima County and information regarding the Net-Zero code in general

    Daniel Ice
    Green Building Program Manager

    Pima County Building Safety and Sustainability

    (520) 724-6493

    Department Directory
    Department Feedback Form