Building Energy Reductions: Windbreak Optimization

Wind tunnel model studies of houses are used to determine how one can best reduce the surface pressure variations from wind and the associated air infiltration, emphasizing the correct placement of suitably modeled coniferous trees. The trees are shown to have energy-saving potential by converting directed kinetic energy of the approaching wind into random turbulent energy by passing the air through tortuous paths in the tree crowns. This reduces the pressure gradients on the windward walls which are a prime region for air infiltration. The most cost- and energy-effective windbreaks are those that selectively protect against the prevailing winter winds, use as few trees as possible, and are placed at least two tree heights upstream. Underpruning and poorly designed openings through the trees, such as driveway access, were shown to enhance air infiltration effects. Using as few as three trees, 3% fuel savings were estimated. When a planting pattern affording general protection was analyzed, it was estimated to achieve higher than 10% savings in energy for heating.