Insulation

[MYater]

Okay, I know there are several threads on this after looking through the forums for the last several hours, but I have come to two final questions;

1. Why is there not a sub topic just for insulation? There are clearly enough threads on it spread throughout the forums.

2. I think I am going to use a 1 inch later or foil backed XPS(the yellow closed cell foam) found at home depot, a layer of Reflectix and then a 1/2 inch layer of XPS finished up with another layer of Reflectix, finalized with the inner skins. I'll put the wiring in between the layers of XPS. Any thoughts good or bad on this?

[Bauxter]

MYater, I generally like the idea of rigid foam. I used something similar under the floor, screwed and glued to the underneath side of the plywood. (No easy spot for rodents to build condos). I have not insulated the upper shell yet, but am about to. I like the idea of using rigid insulation, but I also like the sound deadening properties of fiberglass or other similar products. I was toying with the idea of refelctix all around, on the first layer against the shell, then rigid in the first wall cavity ,up from the floor channel to the first cross-brace, then 2 layers of batting for all cavities above the first cross-brace, (not sure which product yet..fiberglass or "something like it but less water retention and mildewing properties". Two layers, so I can add electric between layers.
My thoughts about having rigid in the bottom cavity was to reduce the risk of rodent populations and minimize water retention in the insulation at the lowest point of the shell wall.
Its a great question. Hopefully the definitive answer will show up before I buy my supplies .
But....You have a 1948, I have a 1973. It almost seems sacrilegious to update a 1948.

[MYater]

Well plans slightly changed. I don't know if it will be a good change our not.

I picked up the 1.5 inch XPS instead and began the figuring to install it in the front dome area. Yay! In never measured the front window wall thickness. So it is only 7/8 thick around the window tapering up to 1.5 inches at the first bulkhead station. So the new plan is thinner XPS with multiple layers of reflectix to thicken it up in suppose. The closer area to the first bulkhead in will probably be able to double up some, but it means another trip to the store.

I'm just glad it's had not bought all the insulation for the "whole thing" already and would have to return some of it.

[Belegedhel]

I'm in the middle of the same dilemma, but I'm moving on.

I have wasted countless hours dwelling on this, and have finally begun the following: I am using a ridgid foam styrofoam sort of stuff with a reflective layer on it in the lower portion of all the walls. Two layers, 1/2" thick each, one with the shiny layer facing out, one with it facing in. Got it at Lowe's, it was called something like "Max R."

Above that, I am using a yellow fiberglass batt with a reflective layer on it instead of the conventional brown paper. The magic of this stuff is that it is designed to wrap ducts, and is only 2" thick out of the bag, so no trying to split a 3.5" in thick roll of the pink stuff, plus I get the psychological bonus of a shiny layer.

So my guesstimate is that I will have ~R6 in both sections. I have experimented with the fiberglass batt, and despite the urban myths, it doesn't "wick" up liquids, generate mold, etc.. I put the solid stuff lowest so that if critters get in there, they won't find an immediate nesting material, and if water drips down my wall, perhaps it will dry more readily if it isn't in a fiberglass batt.

The deal with all of these reflective insulations, is that you HAVE to have an air gap to achieve their proposed R values. I've heard Prodex quoted as having an R value of 16 if installed on the underside of a 2x6, so that you have 5.5" of airgap on one side, and practically infinite airgap on the other (like on the inside of a cathedral ceiling in an attic). If you put that product in a 2x4 wall, the R value drops dramatically. If the delta is linear, then in a 2" wall depth, the R value will be ~4 would be my guess. I'll get a marginal amount of airgap in the solid styrofoam section, and no airgap in the fiberglass section, but my estimated R value in neither place is dependent on the radiant barrier, so anything I gain is pure gravy. The windows have practically no R value, and there are lots of them, so all this obsessing over maximizing the R value is probably for naught.

That being said, I can't help obsessing...If I filled the entire wall space with a ridgid foam, I could get approaching R-9, which is the best I can find. BUUUT...to get a solid layer of foam in the wall, I would have to machine the heck out of it to fit it and make it bend with the shell, and cut channels for wires to go through, etc., etc....Eh...the fiberglass is pretty easy.

I'm still trying to find a bit of the Roxul, which is a "rock based wool insulation" that is very high temperature resistant. Wanted to install it behind the refrigerator and in a section of the roof where I might have a chimney going through, but it is unobtanium so far.

Whew....

[Wabbiteer]

it doesn't "wick" up liquids, generate mold, etc..

Envision starting with 500 hours in 98% humidity, and temperature changes forcing condensing atmospheres - a vicious closed cycle - then the microbiological junk that's everywhere on the planet have a go at homesteading where traces of organics are found - your cooking smoke, tree sap and the like carried in by rain, plywood tea... then it's Katie bar the door.

If we're deliberate with leak prevention, the positive pressure soap-bubble check annually and a sheltered storage spot then fiberglass aces the requirements. Its the long term neglect by Joe Somewhen that turns fiberglass rouge.

[MYater]

Originally Posted by Belegedhel

I am using a ridgid foam styrofoam sort of stuff with a reflective layer on it in the lower portion of all the walls. Two layers, 1/2" thick each, one with the shiny layer facing out, one with it facing in. Got it at Lowe's, it was called something like "Max R."

In only have one really big complaint with the use of the Max R Styrofoam made by Dow is think, styrofoam breaks down too easy. I'm not talking about being biodegradable, in mean the individual cells separate and break apart.

Just like the DOT and helmet manufactures tell you that you should replace helmets (motorcycle, bicycle, hard hats, etc.) every two years. After a two year period the connection between the individual beads starts breaking down and then moisture can accumulate and mice are able to burrow again.

As a real world example that everybody has seen but may not have put together: think of those chinsy white styrofoam ice chests that you can get for five dollars or so. They work great for that summer that you use it, and it holds up quite well. Then it ends up sitting in the garage to be used the next year. By the third year the lid ends up being picked up by the wind only to be blown against a tree or something and a big corner breaks off, or just in half. It is due to the contact bonds between the beads breaking down.

And yes I am aware that the sunlight (uva/b) accelerates the breakdown process, but I'm thinking that I don't want to install something that is know to start breaking down its bonds in two years.

I do hope that yours lasts as long as possible, I just don't think I want to take the chance.

[Belegedhel]

I chose the Max-R because it flexes a lot more easily than any of the other rigid foams. It is held together with a film on either side, but when you cut it with a knife, the little styrofoam balls end up everywhere. Once I put the inner skins back on, I will cross my fingers and hope never to see inside the walls again. Ignorance is bliss!

On the fiberglass, my trailer spent its entire life in Florida, where the frame rusted away and the floor rotted, but the major problem I found with the ancient fiberglass insulation was that mice had gotten in there and made a habitrail. Even the stuff that had fallen into the bellypan wasn't growing mushrooms, it was just dirty. So, I figured it was an acceptable risk to put fiberglass back into the trailer--I'm thinking keeping it out of the ready reach of rodents, and puddling water ought to at lest be an improvement over the original design.

[65will]

When I did my 69 Trade Wind I sprayed back in the spray foam That I removedfrom the floor. But since then I have built a metal building Quonsit hut style, and insulated it with Prodex Total from Insulation for Less an on line company.If I do my trailer again I will use this. Check out ther web site. This is Just an opinion, which I'm sure there will be many. The air gap used is 3/4 of an inch. It works great in my building.

[MYater]

So I started with the 1/2" foam installation today. I'm going to need more liquid nails! But it is coming together now.

The blank lines are the black tar and rubber looking spray flex from a can. The center I applied pretty heavy though just in case.

[Bauxter]

I would check how the liquid nails is doing tomorrow afternoon. I used Liquid nails to adhere wire clips inside along the roof for the re-wiring I am doing. a third of them fell today, as the heat seemed to melt the liquid nails. The liquid nails seemed to have already set-up last night, but the morning sun must have warmed the adhesive too much.

I am still scratching my head trying to figure out what the best adhesive is for this type of application.

[MYater]

Originally Posted by Bauxter

I would check how the liquid nails is doing tomorrow afternoon.

I was worried about that early on since the outer skin was hot to the touch, but before I called it quits tonight I had the whole dome built in, and hopefully they all help each other out. Just needs to hold until I get the reflectix taped in place and I'll put the inner skin back in place.

[MYater]

Originally Posted by Bauxter

I would check how the liquid nails is doing tomorrow afternoon.

I am still scratching my head trying to figure out what the best adhesive is for this type of application.

Went on a kayak trip this morning and didn't get back until after 3PM. Due to the tension in an arc it was all still in place, but the liquid nails was cured up and holding where I made a test pull. I added the last bit of insulation I didn't get to last night and started with the Reflectix.

Ran out of time again today. Perhaps tomorrow before work I can foolish it up and get the half done riveted in place.