Floor insulation

[Whywalk]

Ready to lay flooring insulation.
I’ve been told—given the very very good condition of the metal sheeting—that I don’t ‘need’ to paint it first. But it’s a shortie and we’re only talking ~15 feet, so I want to paint it. Rustoleum, yes?
Now, the rigid insulation: should it be polyiso R-max or the pink / blue stuff (xps?).
Please give your reasoning; I’ve read so many conflicting “use THIS” responses.
Also (if it matters) I am NOT framing the floor, though I will sheet over the foam with plywood.
Thanks!

[o1marc]

No matter the condition, painting the floor is preventive maintenance, Rustoleum is what a lot use. IMHO, I doubt you would see much performance difference between the foam boards.

[Whywalk]

Originally Posted by o1marc

No matter the condition, painting the floor is preventive maintenance, Rustoleum is what a lot use. IMHO, I doubt you would see much performance difference between the foam boards.

Yes, I thought preventative was a swell idea.
Thanks for taking time to respond.

[Whywalk]

Originally Posted by o1marc

No matter the condition, painting the floor is preventive maintenance, Rustoleum is what a lot use. IMHO, I doubt you would see much performance difference between the foam boards.

Yes, I thought preventative was a swell idea.
Thanks for taking time to respond.

[Whatthefak]

The difference in polyiso and xps from what I've been reading, is only in cold so if you plan on staying out of harsh cold you shouldn't see a difference

[Whywalk]

Originally Posted by Whatthefak

The difference in polyiso and xps from what I've been reading, is only in cold so if you plan on staying out of harsh cold you shouldn't see a difference

I’d like to be prepared for any situation 👍
I think I’ll go with the XP’s on the floor.
If I’ve researched enough, am I correct that I won’t need a vapor barrier underneath either the foam or plywood?

[o1marc]

Originally Posted by Whatthefak

The difference in polyiso and xps from what I've been reading, is only in cold so if you plan on staying out of harsh cold you shouldn't see a difference

And just how significant is that difference?

[Whatthefak]

From what I've read it's not huge, the bigger difference is in the foaming gas from brand to brand and how fast they off gas and lose R value

[joeblack5]

There is a no doubt biased article from owens corning. Search polyiso versus xps.

Xps absorbs more water if exposed and at 15f the r value drops from 5 to 2 . . so for the floor I would stay away from xps.

Later j

[Whatthefak]

Originally Posted by joeblack5

There is a no doubt biased article from owens corning. Search polyiso versus xps.

Xps absorbs more water if exposed and at 15f the r value drops from 5 to 2 . . so for the floor I would stay away from xps.

Later j

I've read alot on it from different sources. The gist of what I got is there are people in the industry pushing for better real life measure of R value because of the life span of foaming gases, some have larger molecules and permiate the foam cell wall more slowly and the gases have better insulation property than air.

By the numbers alone xps looks better and does perform better in heat, but the cheaper pink board seems to be longer lived and performs the same in heat and cold, but at a slightly lower R rating

I'm not an expert, that's just what I got from researching because I live in Wisconsin and don't want to be cold.

[Whywalk]

Originally Posted by Whatthefak

I've read alot on it from different sources. The gist of what I got is there are people in the industry pushing for better real life measure of R value because of the life span of foaming gases, some have larger molecules and permiate the foam cell wall more slowly and the gases have better insulation property than air.

By the numbers alone xps looks better and does perform better in heat, but the cheaper pink board seems to be longer lived and performs the same in heat and cold, but at a slightly lower R rating

I'm not an expert, that's just what I got from researching because I live in Wisconsin and don't want to be cold.

The pink Owens Corning IS xps.
And now I’m utterly confused.

[o1marc]

Originally Posted by Whywalk

The pink Owens Corning IS xps.
And now I’m utterly confused.

Some, not all.

[Whatthefak]

Originally Posted by Whywalk

The pink Owens Corning IS xps.
And now I’m utterly confused.

Sorry was referring to EPS

[EastCoastCB]

Originally Posted by Whywalk

I’d like to be prepared for any situation 👍
I think I’ll go with the XP’s on the floor.
If I’ve researched enough, am I correct that I won’t need a vapor barrier underneath either the foam or plywood?

XPS and marine ply is what my shorty's getting.

[Whatthefak]

Originally Posted by EastCoastCB

XPS and marine ply is what my shorty's getting.

But you sir live in the warm sun, I get -30 some times.

Good call on the marine ply

Not sure how I'm going yet

[EastCoastCB]

Originally Posted by Whatthefak

But you sir live in the warm sun, I get -30 some times.

Good call on the marine ply

Not sure how I'm going yet

Yeah, but I know folks with less of NO insulation living in buses much farther north than me. And mine is just a cruiser/daily driver/weekend warrior.
Well-once I get around to fixing it.

-30 in a bus would have me driving south asap!

[jimburke77502]

On the subject of the insulation, i would recommend a radiant barrier. Radiant barriers are, in my experience, make a world of a difference. For your plywood, find someone local that carries a product called "advantech". Comparable to 5/8" plywood, but denser, and completely waterproof. Mind you, you have to use the 5/8" and not the 3/4". The 5/8 is a sheeting and has a resin impregnated completely through it. It's also tongue and groove. The 3/4 only has the resin on the edges. You'll also find that the sound deadening properties of this are quite well.

[Biscuitsjam]

Here in Alaska, I can get regular 3/4" plywood for $50/sheet, marine ply for $100, and I can't find Advantech. The floor needs around 9 sheets. $900 versus $450 is a big difference. How important is it in your opinion?

[Tango]

Never saw a Skoolie that didn't have a leak somewhere or get the floor wet from something.


Also never saw regular plywood survive getting wet very well.



Since it will be the "foundation" for everything inside...well...

[kazetsukai]

Originally Posted by Whywalk

Ready to lay flooring insulation.
I’ve been told—given the very very good condition of the metal sheeting—that I don’t ‘need’ to paint it first.

I have a 38' rear-engine. I ripped up the floor then used a wire cup brush to blow off any and all rust, I then primed with Rustoleum rust converter and put two coats of Rustoleum gloss white down. It took a couple hours at best (minus wait times) and its BULLETPROOF- I'll sleep better at night knowing I did it.

I had my tarps fly off in the middle of the night a few times on me when it rained- had pools of water in the corners. Didn't matter- I painted every bare metal surface I could reach and I don't worry about it. I've made drain holes for any place that pockets up water so it can get out when it needs to.