New Attic Grower

I have a ebb and flow setup in my closet and it needs to go in the attic to be more discreet. The problem is temperatures where I live get down to 10 degrees farenheit in the coldest days of the winter, Right now the lows are about 40 degrees which is probably still too cold for my little plants. Anyway I am looking for a cheap way to keep it warm after I set up a grow box up in this attic.

This was my first idea, and it sounds perfect, its a mat you put on the wall that only uses 100 watts and radiates out heat, tell me what you think, my biggest worry is that it does not put out enough heat

CL Indus Tool Electric Heater Low Wattage for Energy-Efficiency