The US Department of Energy (DOE) has funded several research projects, including this study, to assess the effects of site design on building space conditioning energy use. An important strategy being investigated is the use of vegetation for shading, wind control, and temperature modification. The study described in this report has been conducted concurrently with a closely related research project at the Northeastern Forest Experiment Station of the USDA Forest Service in Pennsylvania. The objective of that project is to measure wind-speed reductions and solar obstructions caused by trees around representative houses within typical neighborhoods and to develop an empirical model for estimating these effects based on the physical characteristics of different neighborhoods (Heisler 1989). The objective of this work is to combine the results of the on-site microclimate measurements from the 1989 Heisler study with work in building energy simulation to calculate the energy impacts of the observed microclimatic changes due to trees.