I would like to use foil-faced expanded polystyrene boards to insulate my window at night.* That window is located a foot or two above my electric baseboard heater.** To me it seems like this could create a fire hazard, or at least risk deforming the polystyrene.***
Is there anything simple that I could do to mitigate or eliminate this fire/deformation hazard (if any)? I was thinking that maybe I could make a heat-resistant barrier between the heater and the window, or maybe put a flame-retardant material or coating on the polystyrene. But any solution would be welcome.
Also, is there a good way for me to test the extent of the hazard under "normal conditions"? For example, could I put in a shelf as described above, stick a memory thermometer underneath, and monitor the air temperature below it over an extended period to see how hot it gets?
* That may be stupid, feel free to let me know. I will probably set up a separate question about that.
** Which I always run on "low"
*** In the past, this has not been an issue with the plastic (polyolefin?) film that I put around the window.