On page 28 of the August issue of FMCA "Family RVing " magazine is an advertisement of "Cool It Thermo Tec" products for heat and sound insulation.
It's available at NAPA or on line of course.
I'm redoing my generator compartment insulation so I think I will give it a try.
While it will work well for heat and sound insulation, it will not do much against fire. You might consider backerboard installation before you install the Thermo Tec. Even the backerboard will only buy time against fire as the compartment door will quickly burn. The same for the engine compartment.
The Thermo Tec will be no less than a thousand times better than the black insulation. It's like throwing gasoline on a fire.
Pierce
We used Thermo-Tech 14125 for engine & generator compartments. This is two-sided foil and after cutting each piece to fit, used aluminum tape on edges to waterproof piece. Most stay in place with aluminum tape to hold in place. Hold up after many years and looks good. Used spray glue over existing original insulation in some places.
Amazon.com: Thermo-Tec 14125 48" X 72" Two Sided Thermo Guard Flame Retardant... (http://amzn.to/3lywhzJ)