IvyDE does not seem to honor the setting of the environment variable IVY_HOME, nor does it allow you to configure where you want your Ivy Home to be. It should work like the Ant plugin does, and allow you to configure, at a workspace level, the location Ivy Home.
This is important because for many users, the default C:\Users\<username\.ivy2 directory is not on a fast storage device (like an SSD), and things run much faster with the ivy cache running on an SSD or RAM drive. We are currently using linkd.exe to create an NTFS junction to the location where we want Ivy Home.
This however, is also somewhat of a performance hit as going through an NTFS junction causes some overhead. We can tell, because with a command-line build with IVY_HOME set to an SSD, it completes 30 seconds faster than with the IVY_HOME unset buy going through the NTFS junction point (9:30 vs. 10:30).