Fiberglass insulation that doesn't stay wet or attract mice?

[profdant139]

I'm still getting ready to enclose the underbelly -- a daunting project. I'm using an inch of EPS stryrofoam board, covered underneath with coroplast. I'd rather use 2 inch board, but do not have enough clearance under my water tank.

So I would like to supplement the foam board with some fiberglass batting type of material, stuffed into all of the empty space (especially around the water tank).

But the problem, of course, is that if and when that stuff gets wet, it stays wet. And mice love to nest in it --why not? (I guess they don't get itchy from it, like I do??)

So is there any other similar product that I am overlooking -- something soft and "stuffable," but which does not retain moisture or attract mice?

Thanks in advance for your suggestions!

[DR650]

Could you use metal galvanized hardware cloth over the insulation to seal off the underbelly section and then install the coroplast? Even if you use an insulation that the critters can't use for nesting, they'll find nesting material and carry it back to the rv.

[agesilaus]

I thought about spray foam, but it sticks things together like glue and I'd not want the coreplast glued to the black tank for example.

[rexlion]

If using any spray foam, use high density polyurethane. I think 6 lb density or better, from what I have read. But what about XPS sheets? The pink or blue ones depending on which store you go to. The only problem with them is getting the right glue that will hold them in place... some folks rough up the surface with sandpaper to help glue adhere.

[alfredmay]

Install Ultra Heat around the tanks too. Insulation does not create heat as you know. With Ultra Heat you can create heat and keep it in with the insulation you will add.

I would not try and insulate every nook and cranny. I suggest creating a basement that will allow heated air to move around and keep water pipes warm.

[profdant139]

More great comments! In no particular order, some thoughts --

I am trying to avoid spray foam because it can't be removed easily in case repairs are needed. But I may have to use some of it for a few of the odd shaped holes.

I like the idea of zip lock bags full of fiberglass. I wonder if there are contractor-tough bags that can be sealed up -- something used for construction debris?

In terms of how cold, I know that no matter what I do, sustained temps below zero are out of the question. My realistic goal is to be able to tolerate nights that drop to about ten degrees, with days in the 30s or 40s. Those are typical late fall and early spring temps for the Eastern Sierra and Southern Utah, places where we often travel.

It won't be a 4 season trailer, but three and a half would be great! 😉

I should add that I recently installed an Ultra Heat heat cable on my water tank outflow line, which is the Achilles heel of the water system. I will be posting a report on that project soon.

[RollandB]

You might think of what a buddy did with his after he repaired a tank leak. He stuffed fiberglass into zip lock bags before putting back in. Not a fool proof fix but better than doing nothing. At my local dollar store I can get 2 1/2 gallon zip locks, the box has 5 and is $1

[SteveAE]

profdant139 wrote:

And Steve, they say that EPS closed cell extruded polystyrene panels don't retain moisture -- is that not true? For example, a styrofoam ice chest seems to be perfectly dry after the ice water is poured out.

Dan,
Without researching exactly what you are planning on using, I can't say for sure. But I do know that the commonly available white, trade marked, product called "Stryofoam" absorbs moisture. Interesting comment on the ice chest......but I wonder if the ice chest might weigh a bit more after being drained???? Over the years, I have encountered the remains of a number of these ice chests in and alongside rivers and I can say without a doubt, that they are saturated with water.
I also have several large panels of Styrofoam here that used to be so saturated with water that I could hardly lift them....before I let them dry out for several years in my barn.
Personally I would avoid this product anywhere that it could get wet.

[rhagfo]

profdant139 wrote:
Some great tips! magicbus, I had never heard of encapsulated batts -- I will definitely look into that. John, I could not determine whether Rockwool sheds moisture -- have you used it in similar applications?

And Steve, they say that EPS closed cell extruded polystyrene panels don't retain moisture -- is that not true? For example, a styrofoam ice chest seems to be perfectly dry after the ice water is poured out.

Agesilaus, I was also not aware of the alternatives to Liquid Nails. I like the idea of cementing the foam into place. The only downside is if I have to remove the stuff in order to fix a problem with the fresh water tank.

The bats may shed water when untouched, but cur or rough edges will hold water.
I used the Reflectix foil bubble insulation, it will not absorb moisture.

OP, how cold are you looking to use the trailer in?

[theoldwizard1]

agesilaus wrote:

I know that the pontoons on pontoon boats are made out of closed cell poly that is exposed 24 hr/day to water and they do not become water logged. I used foam panels when I built my house and the panels were stacked outside in Florida weather for months and showed no sign of water absorption. So I am very doubtful of that claim.

Boston Whaler boats have closed cell foam injected between the inner and outer "skin". After many, many year of hard use they develop some cracks and water can get in between. They slowly "gain weight". Obviously it is water but drilling hole does not let it drain out !

[free_radical]

profdant139 wrote:
I'm still getting ready to enclose the underbelly -- a daunting project. I'm using an inch of EPS stryrofoam board, covered underneath with coroplast. I'd rather use 2 inch board, but do not have enough clearance under my water tank.

So I would like to supplement the foam board with some fiberglass batting type of material, stuffed into all of the empty space (especially around the water tank).

But the problem, of course, is that if and when that stuff gets wet, it stays wet. And mice love to nest in it --why not? (I guess they don't get itchy from it, like I do??)

So is there any other similar product that I am overlooking -- something soft and "stuffable," but which does not retain moisture or attract mice?

Thanks in advance for your suggestions!

How about some sprayed in expanding foam?

[theoldwizard1]

The only insulation that will not hold water is CLOSED CELL FOAM.

Insulation actually gets it insulative property by having tiny air pockets. If those pockets are open, they will hold moisture. Then only way to remove that moisture is to place the material in a vacuum and lightly warm it.

As for keeping rodents away, liberal amounts of cayenne pepper.

[agesilaus]

profdant139 wrote:
Some great tips! magicbus, I had never heard of encapsulated batts -- I will definitely look into that. John, I could not determine whether Rockwool sheds moisture -- have you used it in similar applications?

And Steve, they say that EPS closed cell extruded polystyrene panels don't retain moisture -- is that not true? For example, a styrofoam ice chest seems to be perfectly dry after the ice water is poured out.

Agesilaus, I was also not aware of the alternatives to Liquid Nails. I like the idea of cementing the foam into place. The only downside is if I have to remove the stuff in order to fix a problem with the fresh water tank.

I know that the pontoons on pontoon boats are made out of closed cell poly that is exposed 24 hr/day to water and they do not become water logged. I used foam panels when I built my house and the panels were stacked outside in Florida weather for months and showed no sign of water absorption. So I am very doubtful of that claim.

[profdant139]

Based on a little googling, it looks like the encapsulated batts are not really moisture-proof -- they have a moisture retardant barrier.

But that gives me an idea -- what about stuffing fiberglass batts into heavy-duty bags, sealing the bags, and then stuffing the bags into the empty spaces around the tank?

If properly sealed (a big if), the bags would completely exclude all moisture and would protect the fiberglass.

The fact that I have never heard of this technique makes me doubt that it would work . . . .

[profdant139]

Some great tips! magicbus, I had never heard of encapsulated batts -- I will definitely look into that. John, I could not determine whether Rockwool sheds moisture -- have you used it in similar applications?

And Steve, they say that EPS closed cell extruded polystyrene panels don't retain moisture -- is that not true? For example, a styrofoam ice chest seems to be perfectly dry after the ice water is poured out.

Agesilaus, I was also not aware of the alternatives to Liquid Nails. I like the idea of cementing the foam into place. The only downside is if I have to remove the stuff in order to fix a problem with the fresh water tank.