Insolation transmission through a deciduous tree canopy: a winter study

Abstract

This study measures the shading properties of tree branches as they affect the amount of available sunlight (insolation) reaching structures placed within the visible tree shadow. Measurement was accomplished by placing a grid in throughout the entire shadow pattern formed, by each study tree between the hours of 9:00 am and 3:00 pm. Data was collected at each point of the grid to determine the percent insolation blockage or penetration, through a tree canopy. This data was then transferred to a graphed tree shadow pattern and interpolated to create tree shading density contours in the tree shadow pattern. Data was analyzed to determine the effects of sample tree shadow patterns upon the passive solar heat gain of windows located within the tree shadow.

This study offers as a guide to future research, the beginning of a tree typology. The typology categories trees commonly grown and available in Virginia, into form and size categories. The typology also begins to assimilate data collected by other researchers on summer and winter canopy densities, leaf drop, and leaf onset periods. The typology creates a framework for future research and serves as a means to record which trees have been investigated, and which have not. Another attribute of the typology is its potential benefit to designers. It can be utilized as a tree selection tool for energy-conserving landscape designs.

Several additional questions and suggested improvements for data collection have been provided for those who care to continue research into this area.