We have a 2002 Fleetwood Terra (F53 V10 gasser). It's not the bottom of the line and certainly no where near the top. I suspect there's considerable insulation with other years / makes / models.
So I line the doghouse with Thermo-Tec insulation. It helped some (heat and noise) but still find my voice is a bit hoarse when we arrive at our destination. I usually travel with racing buddies who are much noisier than the DW. You can listen for so long but eventually you have to talk . . . with force. Over 4 - 5 (or 10) hours it adds up.
I looked at lining the firewall and bottom of cockpit with something. It looks pretty difficult to do. Easy if you're in a manufacturing stage, difficult with finished product.
Maybe I should have my Line-X buddy just shoot the whole thing, fuses, hoses and all . . . . . :D
I wanted a DP when we were looking. Now I know why. A DP wasn't in the budget.
Best,
- bob