Modern residential land development has trended toward densification, resulting in limited greenspace on individual parcels. As a result, land developers and homeowners are often constrained for space to plant shade trees. This can result in suboptimal placement of shade trees for the provision of energy conservation benefits. Using a simulation program called EnergyPlus, we examined the effects of existing trees on the energy consumption of recently constructed homes in three U.S. cities with distinctly different climates: Metro Minneapolis, MN, Charlotte, NC, and Metro Orlando, FL. Remote sensing was used to identify placement of existing trees around the homes, revealing that there were 1.5 to 2.9 trees within 15 m of the homes on average. These existing trees, when modeled as large-stature deciduous trees in the simulator, provided average annual energy conservation benefits per parcel of 14 kWh (MN), 25 kWh (NC), and 44 kWh (FL). We then developed an alternative tree placement strategy that spatially reconfigured the existing trees to both minimize space conflicts and maximize energy savings. This alternative strategy significantly improved annual energy savings per parcel to 57 kWh (MN), 47 kWh (NC), and 103 kWh (FL). Our alternative tree placement strategy was equally effective as the conventional strategy (always plant a shade tree on the west aspect) in MN and NC, but not in FL. However, the alternative strategy was more responsive to space constraints and therefore could be used to maximize energy savings while concurrently minimizing space conflicts between trees and site uses.

Expanding urbanization, characterized by increased impervious surfaces and decreased tree canopy, is contributing to rising urban temperatures. This trend has implications for energy consumption and human health, which urban trees may help mitigate by casting shade upon building surfaces. This study looks at how tree form and placement can improve on current shade tree planting guidelines to more effectively use shade trees to offset this trend. Shade provision is not only a function of tree characteristics but also daily, seasonal, and latitudinal variability in sunlight exposure. In order to understand how these variables influence shade provision and to evaluate existing tree planting guidelines, a computer program called Shadow Pattern Simulator was employed to quantify shade cast by a single tree upon a prototypical residential structure in four U.S. cities. A total of 576 shade simulations showed large trees situated within five meters on the east or west aspect of the structure provided the greatest amount of shade during the cooling season. The simulation results affirm existing tree planting guidelines in the northern latitude that recommend planting shade trees on the east or west aspect while avoiding tree plantings on the south to minimize the heating penalty of unwanted shade in northern latitudes. However, planting trees on southerly aspect should not be discounted in southern latitudes because the shorter heating season lessens the detrimental heating penalty of unwanted shade while providing much-needed cooling season shade.

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