The upcoming BlendMe add-on promises to easily integrate external analysis tools into Blender.
Allan Brito writes:
For architectural visualization artists using Blender and trying to design green architecture wasn’t that easy until today. The use of third party tools like SketchUp and scripts to use softwares like EnergyPlus, added several steps to the visualization workflow. Last week I was told of a new Add-on for Blender 2.5 developed by an artist/developer called Mark Pitman that will change the way we use Blender for architecture. The BlendME Add-on allows you to use several options to run environmental analysis without leaving Blender.
BlendMe isn't available yet, but when it will, it will be commercial/donation based add-on.