Spray foam insulation

[brendalt]

Has anyone used spray foam insulation on the underbelly of their fifth wheel or have any opinion on using this for insulation? Last year, somehow the insulation in the underbelly of my fifth wheel became soaked with water and while I was driving down the highway, hit a bump and a portion of the underbelly fell out due to weight of the insulation. I had to pull out the portion that had come loose and fallen out - a piece about 4' x 6'. I was thinking of getting a foam insulation kit from Lowe's to cover that area.

[pianotuna]

Steve,

That was not my experience with open cell foam.

[StirCrazy]

pianotuna wrote:

StirCrazy wrote:

pianotuna wrote:
be sure to use closed cell foam.

I would cut foam boards to below size and spray foam the edges.

I'm not sure I would use closed cell. it does have a higher insulation rating, but it is not flexible at all and if you have a leak it wont let water thru.

open cell is still r3.4/in it is flexible so wont crack in a application prone to movement, and will allow water to slowly drain if you have a leak.

Steve

If you use open cell the insulation may become saturated with water. Then when it freezes and thaws may have a right mess, including such desirable items as black mold.

it drains and dries out, that's why the building code here is starting to favor open cell foam. both types of foam are mold resistant and both types can have surface mold between the insulation and the substrate it was sprayed to due to condensation. this is more common in OSB roof sheathing though, which is why it is not common to spray the underside of the roof and turn the attic into a conditioned living space.


Steve

[pianotuna]

StirCrazy wrote:

pianotuna wrote:
be sure to use closed cell foam.

I would cut foam boards to below size and spray foam the edges.

I'm not sure I would use closed cell. it does have a higher insulation rating, but it is not flexible at all and if you have a leak it wont let water thru.

open cell is still r3.4/in it is flexible so wont crack in a application prone to movement, and will allow water to slowly drain if you have a leak.

Steve

If you use open cell the insulation may become saturated with water. Then when it freezes and thaws may have a right mess, including such desirable items as black mold.

[StirCrazy]

SDcampowneroperator wrote:
Owner heat traced water lines and tanks, He still froze up

ya when they did my floor of my addition they made me build covers around the plumbing so that they were open to the floor above but insulated below. when they sprayed the heating runs they did each side and then the bottom so the top had nothing between it and the floor. they said when they encapsulate water lines they can freeze and for the heating vents the floor heat will keep the a "room temp, if they insulate all the way around them you will get a blast of cold when your furnace starts up.

Steve

[StirCrazy]

pianotuna wrote:
be sure to use closed cell foam.

I would cut foam boards to below size and spray foam the edges.

I'm not sure I would use closed cell. it does have a higher insulation rating, but it is not flexible at all and if you have a leak it wont let water thru.

open cell is still r3.4/in it is flexible so wont crack in a application prone to movement, and will allow water to slowly drain if you have a leak.

Steve

[pianotuna]

be sure to use closed cell foam.

I would cut foam boards to below size and spray foam the edges.

[LanceRKeys]

I bought sheets of 2” thick foam insulation boards and cut them to fit. Worked well and easy to get off and back on if (when) you have to work on your rig.

[SDcampowneroper]

Ive seen it when someone had a pro insulation co. sprayfoam the belly of a 5er. Owner heat traced water lines and tanks, He still froze up . What a mess to try to fix. Best insulatation improvement is to keep the airspace around water systems and insulate under. with hi density foam panels.
with 2 of my TTs we wintered over in in Canada we heat traced water systems, dropped the axles screwed 1 1/2" pvc to the frame pulled out the Fiber glass then used 3" of rigid foam (r5/") and put the coroplast underbelly back on.

[riggsp]

Many years ago when I worked at a Ford dealership that sold RVs at TTs, I worked on a class A that was insulated with spray foam from the factory...I had to chisel the foam away to get access to the wiring to repair an electrical problem...There is no way I'd do that.

[agesilaus]

I've used the small canned stuff and it works when appropriate. But the underbelly?
1) The Cost
2) How will you get to the stuff in the underbelly
3) The polyurethane is glue it would stick everything together

Just use two or four inch sheets of the insulation board