Oil & Gas appliances are recommended to have insulation, but not required.
A minimum 1” clearance is needed from the exterior of the masonry structure to combustibles.
Two types of insulation are available:
TOP Mix is a Vermiculite based poured insulation and contains NO asTOP-os
TOP Wrap is 1/2" thick Foil-Faced Ceramic Wool Blanket that provides the zero clearance requirement