Insulation question

[RVcircus]

Due to water issues, I needed to remove the insulation from the belly of our travel trailer. We originally has batting with a waterproof underbelly material as a barrier.

My question is, are there any better options available? My concern is that the material was originally between the steel rails and the joists. To properly seal it now I'm thinking of insulating it and then sealing sections of coroplat between the frame rails on the inside and frame rail & siding on the outside. I'm not sure if theres any real way to use the same material that was there with any success.

Has anyone used a spray insulation? I was also thinking of using an automotive undercoating to waterproof it before the insulation and then seal it up as best I can.

Any advice would be appreciated.

[RVcircus]

Thanks everyone. It looks like foam sheets may be the way to go. I'm a little gun shy with moisture given the repairs I'm making now and am thinking watertight isn't the way to go. My trailer was leaking through the roof and rear wall and the water was trapped in the underbelly ( I had to cut the fabric to let it drain).

I've also used rock wool insulation around the fireplace and have a bags around that I would use if I feel like doubling up.

[nomad297]

You could hire a residential insulation company to spray the entire underbelly with foam. I see these guys spraying during new construction and I am amazed at how good they are at controlling the spray to allow for the perfect amount of expansion. Any overspray is very simply rasped down.

You would want to spend some time on thought and preparation of areas that you might not want to spray or draw a nice diagram with good measurements of where certain things are in case you need to cut through the foam for any reason in the future.

Bruce

[westend]

There have been a few guys on the Forum that used a contractor's spray insulation and had good luck with that. It is the most expensive way to insulate under the floor and considerations have to be taken for wiring, heating, and plumbing.

I'd suggest to follow Larry's lead and use a foam board to replace the batts. You could also use a combination of both. Basically, the most insulation you can get under the floor is the route to take. It will make your trailer a lot more comfortable in all types of weather. The price of batt insulation is so low that replacement of the original is matter of fact, the risk of mold or insulation matting also influence this decision.

If you really want a tight under belly solution, you might want to look into using light aluminum panels instead of Coroplast. Installed right, the aluminum sheet should out last the plastic barrier.

I'm not a believer in excess moisture issues or allowing for catastrophic water problems. I've installed foam board directly to the bottom of the floor sheathing and experienced no issues. In my Starcraft, the floor sheathing was removed and the original Celotex insulation, installed over aluminum sheet barrier had not degraded from any moisture. This was a period of 40+ years.

[hddecker]

X3 Don't spray. Also don't use undercoating, if you don't have an absolute seal moisture can penetrate and it won't be able to dry out, next thing you'll be replacing your floors.

Check Home Depot, in Canada they have a product called Roxul rock wool. The fire barrier version can be totally saturated with water. It can be taken out and dried if wet and retains it's shape and R-value.

I wouldn't worry about trying to get the coroplast sealed up totally, if you do get any water in the belly pan you want it to have some way to get out.

[LarryJM]

edbehnke wrote:
don't spray, it'll be heck trying to repair something in the future.

another thought would be rigid insutaltion i.e. blue 2 inch rigid.

My enclosed underbelly did not have any insulation in the void and when I sectionalized it I added a bunch of the foam type board insulation. I didn't try and do a first class job like taping sections together, etc., but I figured whatever I could easily add couldn't hurt and any help could only be a plus and the added weight was minimal.

This shows a picture of a section of the new underbelly removed and the new insulation that I added. This is at the very rear of the trailer and that duct is the last one and the tank on the left is the black tank and the grey is about 10" in front of it. I didn't want to put insulation under the actual tanks so the air space around most of them could be heated by the ducts. The insulation runs from frame rail to frame rail and all the way to the rear of the trailer.



This shows the additional R-5 insulation in the forward area of the trailer. The insulation runs from around the front of the FW tank all the way to the front of the trailer and from frame rail to frame rail. The heating ducts were secured to the floor of the trailer in this area and are now above the insulation in the void there.



The shaded grey shows the approximate areas that additional R-5 insulation was added. The blue are the heating duct runs and three floor registers. The entire floor area of the bottom of the trailer is 195sq ft of which 156 is between the frame rails and I put 112sq ft of insulation in that area.



I haven't done any decent testing to see if what I did helped much and not sure how I could determine it anyway and as I said above I figured it had to be better than nothing so it is what it is.

Larry

[mosseater]

If you want batt insulation that doesn't sag, doesn't turn to slop when wet, and dries out with ventilation, check into Good Shepherd insulation. Made from real sheeps wool, it is impervious to moisture and holds it's form even in a downpour.

[edbehnke]

don't spray, it'll be heck trying to repair something in the future.

another thought would be rigid insutaltion i.e. blue 2 inch rigid.

[edbehnke]

don't spray, it'll be heck trying to repair something in the future.

another thought would be rigid insutaltion i.e. blue 2 inch rigid.

[newman_fulltime]

use astrofoil