HFSS IE: Scattering in background media

I would like to validate some results I have of the scattering of a sphere using Mie Theory in HFSS. My sphere has a dielectric constant E1, and is suspended in a media of dielectric constant E2.

When I draw a large region around my sphere with the media dielectric E2, the solver starts to mesh the entire area, which I believe defeats the purpose of using the IE solver? Does anyone know how I can change the "media" dielectric in HFSS?