Insulation for ceiling?

[IslandStorm62]

I am getting ready to put up the walls and run my spars from each wall; my issue is that the spars are 1" x 2", so if the y are installed wall to wall "vertically", that would give a 1.5" ceiling depth (space) between roof and headlining. At least this is how it looks on the Generic Benroy plans.

I guess I am wondering if everyone is using 1.5" thick insulation for the roof?

On the other hand, if the spars are installed wall to wall "horizontally", giving a 3/4" ceiling depth (space)would that not be more practical?

Of course this creates another dilemma...the last spars that support for the hatch needs to be "doubled and installed vertically for strength.

Can anyone give some clarity?

Thanks.

[tamnalan]

I installed them vertically. The 1.5" insulation won't hurt and your teardrop will be structurally stronger. Assuming you'll use some sort of ceiling vent - what is the vent's minimum thickness?

Oh, and my teardrop is tiny. Only 3' x 7', by 44" tall inside.

My $0.02

[IslandStorm62]

Thanks, I did not think of the vent. I will be using the same standard 14 1/4 x 14 1/4 trailer vent.

I'm guessing that the vent is "a" if not the driving factor for the spars orientation. Looks like I'm going vertical to ensure I have consistency for the hatch and the vent.

Anyone else have additional info for me to consider.

Thanks again.

[mezmo]

Installing the longest cross-section dimension of a piece of 1x in the
vertical position is always stronger as there is more material to resist
the tension and compression forces the span length imparts. The most
straightforward way to deal with insulation is to use the same thickness
as the spar's downward projection, then cover the combined spars and
insulation with the interior sheet covering. If that is a structural
material, like 1/8 or 1/4 inch plywood, and you glue that all together
you'd have a sandwich style torsion panel resulting from that. [Remember
everything glued tightly together reinforces each other and reacts as 'one',
or lends its strength to the other, when reacting to forces, sometimes quite
synergistically - so to say.]

If you wanted to put in thinner insulation between the spars, for the look
of it, say, just measure and cut the insulation to fit the needed dimensions
and cover that with your interior ceiling covering and trim for the resulting
edges. That'd be more time and trouble, and not as strong either, than
the first described method, in my view.

[bobhenry]

As just said a 3/4 x 1 1/2 actual spar should be oriented with the 1 1/2 depth in the vertical. As to insulation sheet foam has always been my choice and no you don't have to buy 1 1/2 foam.
1/2 and 3/4 are most common and somewhat cheaper so 3 layers of 1/2 or 2 layers of 3/4 will also work well. I used butyl tape to help secure the foam to the spars on my 4 x 7 build.

[les45]

A word of caution about buying the 1/2" foam at the big box stores. I needed to fill the 1.5" thickness of my 1X2 spars so I bought the 1/2" foam at Home Depot with the idea of three layers to get the desired thickness. Turns out the foam was actually 9/16" so three layers ended up being too thick. I finally settled on using just two layers with an air gap. Measure the stuff in the store before buying to make sure it is truly the size you are looking for.

[planovet]

For my spars, I ripped 2x4s down to allow for just enough room for 2 layers of the sheet foam.



After first layer:



The second layer covered all the wires.

[Forrest747]

DO NOT GET THE WHITE FOAM. Make sure you get the foam that does not have little beads in it. I did the walls in blue insulation which was easy to work with but the white stuff did not like my cutting tool and had little beads of insulation everywhere and it stuck to every thing. For the roof i did two layers of 3/4 the lower one i would make spaces for the lights and wires and then a solid piece over. The doors also were insulated with the white stuff.


http://s1060.photobucket.com/user/forrest74769/media/Charley/IMG_9547small_zps6f442c73.jpg.html
http://s1060.photobucket.com/user/forrest74769/media/Charley/IMG_8701_zpsea29e11f.jpg.html

[working on it]

Even though I never planned for it, I may end up needing some insulation on my ceiling, also. I painted the 3/4" plywood on both sides with two coats of aluminum reflective silo paint (outside over two coats of poly mix), thinking that that would be enough to shed the heat of the Sun. I read where the reflective ability of just the aluminum (silver) flakes in the paint were comparable to the foil-faced insulation (of course, minus the foam-fiberglass-or denim backing). But, the other day, while testing the battery charger inside the cabin, I was made aware of the heat build-up in the cabin, despite the A/C. I never thought of the fact that the roof/ceiling, though reflective, would still be heated by thermal conduction (from the Sun or inside heat or outside air temp), and without any insulation inside, would keep and transfer that to the cabin below. I should've known that...I've had trucks with no headliner that would cook your brains, until you added even the thinnest headliner as a radiant barrier, whether operating by thermal diffusion or just by creating an air space below the heated steel. So, since I'm sure to be over my trailers goal weight , another few pounds of insulation couldn't hurt! I am considering this http://www.homedepot.com/p/t/100656748?productId=100656748&storeId=10051&langId=-1&catalogId=10053&MERCH=REC%2d%5f%2dNavPLPHorizontal1%2d1%2d%5f%2dNA%2d%5f%2d100656748%2d%5f%2dN#.UbZ9iFko5kQ that could be easily retro-fitted onto my ceiling and sloping front wall. And, since I always intended to have a silver ceiling, the foil facing down would be just a little shinier. I was considering Dynamat, but can't justify that kind of $$$. $18 is more like it. One piece would be all I need. Think it'll help?

[aggie79]

I used 1x2s on edge insulated with 2 layers of 3/4" extruded polystyrene foam. The foam was a little over in thickness so I ran a few passes of the belt sander over it. I used spray foam to fill in around my wiring. In the last picture you'll see a tip that I picked up from someone on the forum. Write measurements to your wiring so when you're attaching the outer plywood you'll know where to not place fasteners.