Insulation behind basement fireplace
 

Hello,

I am in the process of finishing my basement And want to install a gas fireplace for the main heat source. My 1st floor fireplace is installed in a bump out on the side of the house. This bump out also has a foundation which is where the basement fireplace will go. What type of insulation would be best suitable for the foundation walls behind the fireplace? Foam?

Got a picture of where your planning on putting this? Trying picture why in a basement you would use any insulation behind it.
And since foam burns and off gases toxic fumes as it is heated or burns why it would even be used.