The mesh is aluminum. I ordered a 150W CHE this morning and will be replacing the 100W. We covered up the whole top with Styrofoam and the temps rose about +3F just from that. The CHE is sitting about 1/2" above the mesh on Styrofoam spacers. I'd sit it right on there but my curious girl keeps poking her nose at it in a wild attempt to flee; don't want burns. I'm going to see how that temps do with the 150 and then maybe consider a space heater.
Thanks for all the help!