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