First, it'll depend on the type of insulation you have. What are it's ratings for radiant heat and contact heat? Some insulation can take extremely high radiant heat but only half as much when touching the heat source. An example is the Thermotec blanket in the link below. It can take 2000F radiant but only 300F on contact.
Thermo-Tec : Adhesive Backed Heat Barrier
If it's home insulation be careful, most is only rated for max temps below 200F.