There are two basic types of insulation glass and spray foam. Furnaces sweat and foam insulation does not breathe. This makes a good formula for corrosion. Spray foam has a better R-value per inch; however, when subjected to great heat it tends to crystallize and break down. The long term winner is regular fiberglass batting. The use of aluminum foil insulation with air bubbles has not proven up and should be looked upon as a liability. Definitely avoid this insulation.