First let me give much props to people who install tv, internet phones etc. because I don't know how you figured out where anything belongs.
Under a trailer is a big rubberish plastic sheet called the vapor barrier. and under that is a leaf pile of pink insulation.
My HVAC has not worked in over 5 years. Cats have moved into one side of the lining (double wide mobile home) I moved into the house brand new in 1999 but I know nothing about these things. I have replaced the water heater once 4 years ago but it appears that it is full of rust, because we just had a pipe snap, and when we tried to drain the heater, nothing would come out.
A friend repaired the pipe but recommended we start replacing these pipes because they are all brittle. I would like to use this PEX stuff I've passed over while researching my main question; which is : CAN I USE SOMETHING OTHER THAN THE PLASTIC WATER VAPOR SHEET ON THE UNDERBELLY?
I am very frustrated with going under the house and not being able to see what's what. i would like to take some Owen Corning like insulation tiles or maybe some batt with kraft paper and put them against the floor board. Then I would like to put fiberglass duct wrap around the ducts. Then I would like to put pre-slit foam tubes around all of the pipes. I want to see what is what when I'm under the house. How does that sound?