Digital tree simulation for residential building energy savings: Shading and evapotranspiration

Landscaping in general and trees specifically can be beneficial in helping to mitigate several environment problems such as carbon sequestration, urban hear island, reduced air quality due to pollution, and erosion. Yet simulation software programs are often weak in enabling designers to understand analytically and to specifically predict energy savings through the use of landscaping.;The assessment done on existing energy simulation software shows that several programs could not model trees directly. Previous studies have looked at the effect of shade trees on energy use. Different strategies were used to try to model trees in these software programs, and simple case studies were undertaken to verify the results. Two critical potential energy saving features of trees were studied: direct shading on a wall and/or window and evapotranspiration. Shade trees can help in reducing solar gain and thus reduce energy consumption for cooling and should be taken seriously as a climate change adaptation initiative.;The evapotranspiration of shade trees can also change both air temperature and relative humidity in the micro-climate. The evapotranspiration impact of trees has been simulated in DOE-2; the ambient temperatures were changed to estimate the indirect cooling effects of trees in reducing air-conditioning energy use. This methodology was cumbersome. In addition, several of the other software programs could not simulate this effect directly. Different methods had to be employed to achieve this capability.;The final results show the limitations in simulation in practice. Unfortunately, the current energy simulation programs do not have the capability to simulate the tree's effect on building energy usage. For shading, the proposed methodology can benefit in developing integrated tools for simulating the shading effects although there are still many issues unsolved. And there is a need to incorporate evapotranspiration. As a holistic building design tool, the direct and indirect effects of tree should be considered.