Energy Savings with Trees

Abstract

In conventional buildings, trees increase, decrease, or have little effect on energy use depending on general climate, building type, tree species, and tree location. Tree arrangements that save energy provide shade primarily for east and west walls and roofs and wind protection from the direction of prevailing winter winds. Particularly for buildings specially designed to use solar energy and those with solar collectors, it is important to place tree crowns so they do not block sun from collectors and south walls. But conventional houses also benefit from winter sun. Deciduous trees provide better year-round shade than conifers, but do reduce solar energy significantly even without leaves. In winter, reductions in solar energy on south walls by a deciduous tree may be greater than reductions by the same tree in summer. Hence, growth rate and crown shape are important criteria in selecting shade trees, and the placement of trees around the house is important. A summary of research data suggests that the maximum potential annual effect of trees on energy use in conventional houses is about 20 to 25% compared to the same house in the open.