Insulation Question

[egjacks]

I was wondering about the insulation that I want to put into the teardrop. From looking at build pictures it seems that everyone uses some type of sheet insulation. what I was wondering was is there a reason why no one uses regular fiberglass insulation? the stuff that looks like cotton candy? Since no one uses it I am guessing that there is a good reason why, but I can't think of it. Can some of you more experienced types enlighten me?

[DezPrado]

Good Question! Anyone? Anyone?...
For my fourpence worth: The Pink Batts fibreglass was too floppy (wouldn't stay in position for long), the 'R' value too low, and the long time sogginess if it got wet didn't enthuse me.
The sheet poly (or similar) bettered all of those 'problems' for me & additionally allowed a channel to support the electric wires where required thru the panels. It also prvide a measure of support for the Fibreglass cladding I used.

[GPW]

Well, FWIW , the only fiberglass insulation that might work is the "bagged" fiberglass , wrapped /sealed in plastic , and secured at the top so it doesn't sag in the walls ... Probably not as good as the foam , cause ' when you compress the F/glas , you lose some insulation value ... Not the Best insulation for a TD ... JMHO...

[OuttaHand]

I think the reality is that it's a matter of simplicity. If you are going to use bat type insulation (the pink cotton-candy-stuff) then you need to build a hollow space for it to be. To do that you need to build a stud wall like in a home. There needs to be something on top and bottom for studs to attach to and then attach sheet material (plywood, aluminum, etc.) to the studs for interior & exterior walls.

Basically, that's just a whole lot more complicated than building a sandwich of plywood, foam, and plywood. The rigidity of the foam makes it easier to use thinner interior plywood (like 1/4" or so) because you have full support behind it. There's much less chance of sticking an elbow or foot through it while you are entering, exiting, or sleeping.

You also want to compare R-values. The pink stuff is designed to be 3-1/2" thick in a 2x4 wall. It works mostly by trapping air from moving around. That trapped air is your insulation. If you want a thinner wall than 3-1/2", you can compress the fiberglass into it, but you are then trapping less air. Less trapped air means less R-value. That means less insulating.

The rigid foam boards have all the air bubbles "pre-trapped" for you in the foam structure.

Now, mind you, I don't claim to be an expert. I've built exactly one teardrop (which isn't even done). But I can tell you that our teardrop, using just 1" foam (max -- in some places 3/4") in the floor, walls, and ceiling, is plenty warm. Last weekend we slept at a campout here in Wisconsin where the night-time temp got down to 40 degrees or so. About 3am or so I had to push the sleeping bag down because I was hot. So the foam works.

If you're interested in seeing how I used the foam, check out my build log here: http://webpages.charter.net/outtahand/littletow/index.htm

[Artificer]

One thing not mentioned is that the foam can be structural. If you use 1/8" plywood skins, and 1" of foam, you have a fairly strong wall, as long as you get a good foam/skin bond.

What would the benifits of fiberglass insulation be? Ease of installation? Cheap? Thats about all I can think of. Drawbacks would be: less R-value, might settle, itchy...

The floor of my new trailer is 1/4" plywood over 2" of Foamular 250 foam. Its fairly sturdy, and you won't even notice any flexibility once the futon get put in.

Michael

[egjacks]

yeah, cheap seemed to be the biggest plus, I hadn't thought much about the insulation giving much support to the walls.

It might still be an option on the floor...? there wouldn't be anyplace to settle to, and it seems to me that the floor would need the least insulation in the whole trailer, since there should be some sort of mattress to sleep on, providing insulation. Although withe the mattress, maybe no insulation is needed in the floor anyways. what do you think?

[Artificer]

Cheap isn't always... cheap. Forgot to mention, foam doesn't hold water. If your floor gets wet, or the bottom seal isn't perfect, the fiberglass can get sodden. I'm not saying that it will happen, its just a possibility.

The foam doesn't cost that much. Unless you're on a no budget build, I don't think its a place to save money.

My floor was $20 for a sheet of Foamular250. Walls, about $18 total. Ceiling was $30 for 2 sheets of 1.5".

Michael

[OuttaHand]

I built my floor with 5/8" plywood directly on the trailer frame. I used sub-floor plywood because I needed a seam in it. The sub-floor ply has a tongue-and-groove connection system making the seam very strong.

Next I put 1" of rigid foam. I used some PL Premium construction adhesive between the sub-floor and the foam.

Next I cut out a "tunnel" down the middle of hte foam to run three pieces of PVC pipe to use as wiring conduit for running wiring front-to-back.

Next I put down more PL Premium and a sheet of 3/8" plywood for the floor of the trailer.

The floor insulation is there for two reasons: 1) Keep heat in. 2) Keep the floor from getting cold. Those sound the same but the biggest reason to keep the floor from getting cold is to prevent condensation. While sleeping, your exhaled breath contains a lot of moisture. If that moist air touches anything cold it will condense. The condensation on the floor will soak into the mattress, blankets, etc. etc. Insulation in the floor prevents that from happening. The narrow strip down the center that contains no insulation (where the PVC conduit pipes are) is so far in the middle of the mattress area that no moist air can reach it so condensation there won't happen.

[egjacks]

ok, I am convinced, like I said in the beginning, I just needed to find out what those good reasons for not using it were. I am planning on insulating floor, ceiling and walls. I want to have a 3 1/2 season teardrop on as little budget as possible, but I am willing to spend where its important. that and I don't want a soggy trailer.

[GPW]

Jax, you don't need a great deal of thickness to realize an insulation value ... 1/2" of styrofoam would be good in most cases ... Thinner is cheaper ...


-Thrifty is our game! -

[dh]

Remember, you are going to be putting down about 6'' of insulation top of the floor, its called a matress.