I have used catalytic heaters in all of my rv's because 99% of my rving is boondocking. The furnace rapes battery power. I tried the big buddy heaters (I have two) with the hookup to a large propane bottle... Works okay but it seems to create more moisture or alot more moisture than the catalytic... Kept the trailer toasty down to -5 nights during hunting season. The 18,000 btu double ceramic plates warms the trailer fast when you get back from whatever.
Yes, you have to crack a window front and rear but what's wrong with that.
This is the way I do it.... Portable, not attached.