Improved estimates of tree-shade effects on residential energy use

Shade from trees changes building energy use for heating and cooling by reducing the amount of sun that reaches the building. Modeling these changes is difficult and computationally expensive owing to the complexity of the interactions of buildings, sun, and tree. This paper presents a simplified method that averages model outputs, making use of regionally specific frequencies of trees and tree ages, tree-to-building distances, and tree-to-building azimuths. The results are look-up tables that allow energy conservation benefits to be estimated easily and without the need for “on the fly” computations. The simplified values were compared to the more complicated model outputs for 178 properties in Sacramento, CA, with agreement between the two methods of +/- 10%. Limitations and sensitivity of the simplified version are described.