I recently contacted Newmar Customer Service with the same question on using space/area rugs on heated floors to which they replied by advising me that the heating mat manufacturer (Aires) does not recommend using/placing rubber backed or throw rugs on the heated floors due to heat build. Below is what Newmar actually included in their response to me.
Since we already have and use some full fabric, i.e. wool space rugs, we've now taken up the practice no longer using the non-slip rug pads which we previously used under those and generally, roll up and store them away if using the floor heating at the higher settings.
(click on attachment below to expand and read the Don'ts (comment #11) which directs guidance on not using rubber back or throw rugs.