trees

Effects of a coniferous windbreak on electrical energy use in a 66-unit mobile home park in central Pennsylvania were studied during the winters of 1981-82 and 1982-83.

Windbreaks probably are more important for reducing infiltration of cold outside air into houses than for reducing convective heat losses. It is difficult to estimate the magnitude of tree effects on energy use for space conditioning on a year-round basis, but past studies suggest that trees have the potential to reduce winter fuel consumption by 10-25%. Describes several studies of trees as windbreaks and for summer shade. Discusses location of trees with respect to buildings.

Evaluates the space-conditioning energy conservation potentials of landscapes designed to ameliorate building microclimates. The physical bases for vegetative modifications of climate are discussed, and results of past study of the effects of vegetation on space-conditioning energy consumption in buildings are reviewed. The state-of-the-art of energy-conserving landscape designs is assessed and recommendations are presented for further research. Landscaping mobile houses and single family dwellings is considered.

During winter experiments in central Pennsylvania a windbreak, 61 metres long and composed of a single row of white pine trees, significantly reduced air infiltration rates and space heating energy needs in a small mobile home by upto 54% and 18% respectively. Greatest reductions in air infiltration rates occurred with the home at one windbreak height (1H) downwind, even though maximum reductions in wind velocity occurred at 2H or 4H downwind. Space heating energy savings were less sensitive to downwind position, with maximum energy savings measured at both 1H and 2H.

Uses wind tunnel model studies of houses to determine how best to reduce the surface pressure variations from wind and the associated air infiltration emphasizing the correct placement of suitably modelled coniferous trees. Finds that tree crowns convert the directed kinetic energy of approaching wind into random turbulent energy, which reduces pressure gradients on the windward walls, a prime region for air infiltration.