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Hi, I have a plywood floor with carpet on top, in my van.  I saw a video where the builder put mylar bubble insulation under his plywood flooring. Im thinking of doing the same.
I have to take everthing out of my van, strip off the tacked down carpet, pull the plywood that just has a couple of bolts through to cargo floor holes, then lay the insulation and reinstall everything. 
Would i get enough value from this project to make it worth my while?  And while im at it should i install a carpet pad. I would like to have warmer floors. Thanks.
Mylar is NOT insulation, it's a reflective barrier. highdesertranger
No, it will provide very little insulation. If you're going to put anything under your floor, use rigid foam board. XPS or Polyiso. Some people think it's not worth it, I put in 1/2" because I figured why not and because it gave me a nice flat surface underneath my laminate.
The reflective part is literally useless in that situation. And it is never any use as insulation, only preventing incoming radiant heat.

So on the outside, facing out and up is the only time it's worth doing, IMO only when everything is already open and accessible.

Ideally with an inch of dead air space in front of it, jammed up against the outer skin cuts way down on the effect.

The other functionality is as a vapour barrier, sealing against convective transfer and air infiltration.

But plain plastic does better, sturdy 6+ mil dropcloth, very cheap.
(02-09-2018, 02:52 PM)highdesertranger Wrote: [ -> ]Mylar is NOT insulation,  it's a reflective barrier.  highdesertranger

However, the air bubbles do provide minimal insulation. But the plywood and carpet provide greater insulation.
I live in central California and have pretty much decided not to insulate at all after reading the forum. From what I can tell, it would not be necessary in Winter and would not help much in Summer. Is there any other important reason to do it?
I also chose not to insulate my van when I built the interior....I follow the sun so I felt that it wasn't necessary.

What I did do was to install a radiant heat barrier. It has to be done properly or it's a waste of time and money but it's proved to be very effective for me  for keeping out the daytime heat.

It keeps the heat out so well that things like my plates in my upper cabinet are too cold to put food on in the morning...I end up warming the plate so as not to chill my breakfast.... Big Grin
I put two inches of XPS, Foamular 400 on the floor with a 1/2 inch of AB plywood on that. I went with the 400 over the 250 to have just a little more compression resistance. 250 is enough, though. I'm not sure how much is too much or too little, but it is nice to be able to walk bare foot on non-carpeted floor in -15F (-26C) weather. Even at -25F the water sitting on my floor (also boxed in so it is blocked from the heat and is sitting against the wall) doesn't freeze.
Yes if following nice weather can do without.

I don't like being limited that way, and it's a big pain to do it later.