Floor Insulation

bikeforthelight · 10-01-2009, 02:02 AM

So I am gonna be installing the subfloor insulation and plywood this week. Had a question that may sound dumb, but thought I should ask. The insulation is 3/4" and is foil backed on one side. Should that foil side go on the bottom (against the metal floor of the bus) or on the top (against the plywood I am laying as the main subfloor)? Didn't know if it would make a difference, but would hate to lay it wrong, and not have it work the best way possible. Thanks.

vonrock · 10-01-2009, 04:26 AM

This is a good question.

Vapor barrier. Is the foil on your insulation considered a vapor barrier? Is the steel floor of the bus a vapor barrier?

Where I come from, in conventional home construction we put the vapor barrier on the WARM SIDE OF THE WALL. The rest of the wall breathes moisture to the cold side. On a traditional wall, this is not a problem. But what do you do with the floor of a school bus? If steel is a vapor barrier then the rest of your floor has to breath inside the living compartment. That means no vapor barrier, just the steel. Even placing a sheet of plastic or foil right against the steel floor would create a place where moisture cannot escape. This will cause mildew, rot and possibly mould. Once again, assuming the bottom steel plate is a vapor barrier, adding another vapor barrier ANYWHERE else in your floor design will trap moisture, resulting in moisture being trapped between two vapor layers. This is not good.

Based on what I've just stated, if your insulation has a vapor barrier, I don't think you should use it at all.

I've been starting to think about my future build quite a bit and I've been stumbling over the floor/vapor barrier/insulation issue for some time. Hopefully somebody that has been there and done that will speak up.

Papabear · 10-01-2009, 10:48 AM

I laid down rigid insulation with vapor barrier on both sides, with 3/4 plywood on top of that. This was on top of the original 3/4 floor. My steel underneath was in great shape, so I left the original floor in. Anyway, I was going to put down sheet plastic over the insulation then cover with wood. I decided against it and just let the floor breath as it had. The insulation I laid had enough air spaces in it, that I felt it was not a complete vapor barrier. I would put the foil side up on your application. Either way, I don't think it will matter that much, unless your building a family heirloom to be passed down for generations. A lot of us over-engineer. My bus was almost rust free after 18 years. I don't think I will be worrying about it in another 18. If all else fails, we'll drive it to the "property", put it on blocks and call it a guest cabin.
Good luck

bikeforthelight · 10-02-2009, 01:14 AM

Well, I actually found the foam with the foil on both sides, so now I dont have to worry about it. Thanks guys. And Papa....my bus is the same way. A 25 year old bus from Florida with a steel floor that had next to no rust. Im sure it will be just fine for a while to come. I already cleaned and laid paint on the steel floor, so I think I am good. I guess I am just overthinking a bit. But now that the foam is foiled on both sides I can go back to not thinking at all

swhite832 · 10-02-2009, 07:56 AM

I have a tyvek knockoff material left over from a job. Would this be ok to put between the steel floor and laminate flooring?

swhite832 · 10-02-2009, 12:52 PM

Where will condensation accumalate with laminate flooring over plastic sheeting over metal floor? This bus will be mostly used in hot Texas, with two A/C's working overtime.

Diesel Dan · 10-08-2009, 09:17 AM

I'm considering using linoleum squares as my flooring. Could I just lay insulation on top of the metal floor, and then linoleum on top of that? What type of insulation would work in that application? I've never done any kind of flooring before, but I assume the linoleum has to be glued down, or perhaps is self-adhesive? Would the insulation also need to be glued down?

Thanks,
Dan

Diesel Dan · 10-08-2009, 06:23 PM

Quote:

Originally Posted by Smitty

No because the weight of people walking on it will eventually compress ("dent") the insulation. This doesn't happen with plywood subflooring because it spreads the weight over a larger area.
Smitty

Right. I had a feeling that would not work out. I guess I'll just have to stick with the plywood if I go the linoleum route. My main issue is that I need maximum headroom (the reason I got the Thomas high top) and I prefer a hard surface.

Sojakai · 10-08-2009, 06:26 PM

What you need to know, Put plywood over the insulation. It adds a little to the R-value and spreads out the abuse of people walking over the floor. Put your tiles over that. From what I have seen, they are like stickers, Peal off the paper backing and apply. Start in the center of your bus, making sure that you put down as many Full Tiles as you can and getting them as straight as you can, for better appearance where they are in full view. Try to put all cuts against outer walls as its easier to hide them. Too many years of watching "This Old House"...

The house I live in has the sticker Squares. They are about 7 years old and semi stuck down to concrete, but alot of them are pealing up. They were put in within a year before we moved in. Its kinda fun to change the Black and White Checker pattern while walking barefoot... So you might want to see of you can find the Non-Sticker Squares and then use Liquid Nails or another adhesive to keep them down.

Diesel Dan · 10-16-2009, 02:26 PM

Bumping this topic up since it's related to the current discussion...

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