Simulation of a floor heating

Hi all,

I want to simulate a floor heating in a 2D modell. Floor heating systems release about 90 % of heat in the form of radiation and about 10 % in the form of convection. So is it possible to take this situation on one boundary? I tried this with heat-flux and surface-to-surface radiation. But there i can't divided the heat transfer in 10 % heat flux and 90% radiation. I also don't understand the equation in surface-to-surface radiation, what does mean "G".

I hope somebody can help me.

Thanking you in anticipation.

Markus