About i-Tree Design

i-Tree Design allows you to calculate the approximate benefits that individual trees provide. This tool relies on average species growth equations and other geographic parameters that are generalized from city, county, state, and climate region data. Consequently, i-Tree Design is intended to be a starting point for understanding trees' value in the community rather than a scientific accounting of precise values.


Energy

Tree effects on energy use are calculated using the methods detailed in the USDA Forest Service publication, "Carbon Dioxide Reduction Through Urban Forestry: Guidelines for Professional and Volunteer Tree Planters (PSW-GTR-171)." Trees' effects on buildings from shade, evapotranspiration, and wind speed reduction (windbreak) are calculated using an applied reduction factor based on tree type, height, azimuth, and distance from the home. Shade and evapotranspiration effects are set to zero when trees are beyond 18 meters (approximately 60 feet) from defined building footprints. Windbreak effects on use are set to zero when trees are at a distance from the building equaling 35 times the tree height or greater (see: Heisler, G.M. and D.R. Dewalle. 1988. Effects of Windbreak Structure on Wind Flow. Agriculture, Ecosystems and Environment. 22/23:41-69). Because reduction factor calculations are based on data for the United States, these values for other countries should be regarded as approximations.

Past and future benefits are estimated using a forecasting model that includes calculating tree height values for each consecutive year that the model is run. In order to estimate tree height for each modeled year, annual tree diameter growth is estimated based on the length of growing season, species, tree condition, and current tree height. Annual tree height is then calculated based on the tree diameter and species and entered into the use equation.


Carbon
Carbon dioxide sequestration values are derived from species-based biomass equations. Carbon dioxide avoided values are estimated by converting the savings to pounds of avoided carbon emissions. values (kWh and Mbtu) are converted to carbon dioxide using state-based EPA E-grid conversion values.

The carbon dioxide dollar value is based on the average central value estimate of the social cost of carbon as calculated by the 2010 Interagency Working Group on Social Cost of Carbon for the United States Government (see: https://www.epa.gov/sites/production/files/2016-12/documents/sc_co2_tsd_august_2016.pdf).


Stormwater

The stormwater interception and avoided runoff values were derived from county-based i-Tree Eco runs for the conterminous United States using 2010 data. (see: i-Tree Eco Precipitation Interception Model Descriptions)


Air Quality
Air pollutant removal and associated benefit values were derived from county-based i-Tree Eco runs for the Conterminous United States using 2010 data. (see: Tree and forest effects on air quality and human health in the United States.) Air pollutant avoided resource units and monetary values for air quality benefits come from the following sources and are adjusted for inflation using the Produce Price Index (see: Bureau of Labor Statistics Producer Price Indexes):

Abbreviation | Benefit Description | Transmission Rate - Fuel | Transmission Rate - Electricity | Monetary Value:

*Murray, F.J., L. Marsh. and P.A. Bradford. 1994. New York State energy plan, vol. II: issue reports. New York State Energy Office, Albany, NY. Values adjusted based on Produce Price Index. Note: In Canada, median US transmission rates were used and monetary values for CO and PM2.5 were sourced locally.
For more detailed information on urban and community forest assessments, please continue exploring the i-Tree website.


Acknowledgements

  • This tool’s predecessor, the "National Tree Benefit Calculator," was originally conceived and developed by Casey Trees and The Davey Tree Expert Co. With i-Tree Design, i-Tree Cooperators have taken the Calculator to the next level by providing dynamic, site-specific energy use calculations and a long-term platform for technical support and further development.
  • Significant text and graphical content was originally published by the USDA Forest Service's Center for Urban Forest Research through their Tree Guide series of publications. We credit the authors of these publications for this content.
  • Facts about personal carbon production based on driving and flying courtesy of Conservation International.
  • Mary Grunstra (Faculty of Forestry, University of Toronto) provided GIS-based mapping that facilitated expansion of this tool to Canadian locations; this work was funded in part by Tree Canada.

For technical questions about this tool, contact i-Tree support.