How can we shape building form to manage solar heat gain, produce energy, and provide suitable conditions for green roof species?

In response to the inefficiencies and limited functionality of off-the-shelf solar modeling software, we developed our own incident solar radiation modeler. This plug-in integrates TMY (typical meteorological year) data with modeled building geometry, allowing users to conduct insolation studies and visualize results without having to move between different software platforms. The effects of any modifications to building or shading features are displayed in real time, so that we can develop an immediate understanding of the relationship between geometry and solar heat gain. We might choose to view the results as a spatial distribution over the building envelope, which could be used to inform the positioning and performance requirements of glazing. Alternatively, we can view the results as a distribution of solar heat gain over time in order to refine shading devices for greater occlusion in summer and greater exposure in winter.

The output from our solar modeler includes a spatial distribution map of cumulative insolation along with a preview of the solar envelope and a graphic legend, intended to reveal which faces of the building envelope experience the greatest heat gains due to context buildings and external shading devices.

Since development of the core functionality, we have addressed several related topics through the design of additional features for the tool. For a post-occupancy survey of green roof vegetation, we adapted the solar modeler to report results in terms of average hours of direct sunlight. With this feature, plant species distributions can be correlated with solar exposure based on common horticultural classifications. Subsequently, an investigation of photovoltaic output losses due to shading from adjacent buildings was enabled through a novel workflow integrating the solar modeler plug-in with NREL's System Advisor Model (SAM). This modification allows us to generate a custom weather file representing the shading context of each photovoltaic array, which can be imported directly into SAM to create a renewable energy performance model.  
Future development of our solar modeling plug-in will explore the dynamic shading potential of tree foliage. This study will combine published tree leaf indices with in situ measurements to create a library of dynamic shading coefficients that can be applied to modeled tree geometry. With this new feature, we hope to extend our thinking to consider landscape as a functional component of the building envelope and quantify its effect on performance.