1in insulation enough?

Converting Cargo Trailers into TTTs

1in insulation enough?

Postby gbowman » Sat Mar 25, 2017 3:33 pm

I'm at the beginning of my 7x16x7ft cargo trailer conversion. I have installed some with the silver backed foam insulation.
Before I move on I wanted to make sure this would be enough. I live in AR. I have already experienced some nights in the 30's! I plan to add a 13,500 btu AC, haven't decided about the heat strip yet.
Here are some questions!
Is 1in insulation on walls and ceiling enough for summer and winter?
What about sweating? Will it or will it not?
Should I insulated the floor? If so, from the bottom or on top of the subfloor.

I'll just looking for feedback or ideas. Thanks.
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Re: 1in insulation enough?

Postby CoventryKid » Sat Mar 25, 2017 4:08 pm

I installed 1" rigid insulation between the alum. ribs, added a 3" strip of plywood to each rib and installed .5" of rigid insulation in between the plywood strips. Metal taped all the joints and reattached the plywood walls to the plywood strips, NOT the alum. ribs. I've had no problem with sweating in over 2 years.

We spent the winter on southern Vancouver Island in the cold and snow (both unusual for Vancouver Island), but a oil filled radiator and a ceramic heater with a fan kept us toasty all winter.

I insulated our floor on top of the CT floor - others have done it from below. Essentially we have 1.5" insulation in the walls, ceiling, and floor.

Pictures are in my build link below.

I haven't answered your question as to whether 1" of insulation is enough, but I hope this helps.
Doug
Vancouver Island, BC

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GMC Savana Explorer Limited SE hightop conversion van
NEO NAVR 7x16 V-nose aluminum trailer now a comfortable travel trailer

Build: http://www.tusker-international.com/1-trlr-build.html
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Re: 1in insulation enough?

Postby gbowman » Sat Mar 25, 2017 5:28 pm

That does help a lot! A friend of mine suggested what you said about the insulation. That's what got me wondering if my plan was enough!
I love the skylight idea. I was actually thinking of doing the very same thing.
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Re: 1in insulation enough?

Postby defjr333 » Sat Mar 25, 2017 5:36 pm

Although I have not started my build yet, I agree with previous post. Add a strip of plywood along the ribs to stop condensation sweat on screwheads. And if you are going to do that, might as well utilize that extra 1/2" of space created to increase insulation. My only difference will be a 6" raised floor(trailer height will be 7' interior) to provide insulation and to allow plumbing to be inside trailer instead of under it. Dont want to see the black/grey tanks or plumbing. Dont have to worry about catching the pipes on anything. Dont have to worry about freezing.
Doug
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Re: 1in insulation enough?

Postby gbowman » Sat Apr 01, 2017 12:37 pm

Not a lot of replys from people that have only used 1in!!!
Is no response an answer in itself?!?!
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Re: 1in insulation enough?

Postby McDave » Sat Apr 01, 2017 6:19 pm

More is definitely better, but 2" isn't enough either, or 3" etc. Check what is called for in local home construction, you'll find that you won't be able to get enough. Montana calls for R-60+ Do the math... also look at your budget, then tell us what is enough.

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Re: 1in insulation enough?

Postby low277 » Sat Apr 01, 2017 7:42 pm

I think it just depends on how and where you intend to use your trailer. Where I'm at we get subzero temperatures in winter and if you use your trailer in winter and use any kind of heat source it will cause frost on the inside if the inner wall panels are attached directly to the metal wall stud.

Not really a problem if you don't use it in those temperatures but using 1/2 wood over the metal studs will help prevent the thermal bridging that can cause the frosting to occur.

Again it's the owner/builders decision as to how far they want to take it. Really no right or wrong.
NW Minnesota
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Re: 1in insulation enough?

Postby NO David! » Sat Apr 01, 2017 10:02 pm

I used 1" Styrofoam sheets cut to fit between studs in the walls and ceiling, used residential fiberglass in the curved section between walls and ceiling. I have a 6,500 BTU window unit, and live in NW Georgia. It's enough...but of course you can always do better. We have a Styrofoam manufacturer near us, so I just purchased enough 4 x 8 sheets at a bargain to get the job done.

Build details here:
http://www.tnttt.com/viewtopic.php?f=42&t=48345

Air Conditioning here:
http://www.tnttt.com/viewtopic.php?f=42&t=49438#p956281

If I were to do it again, I'd probably use a better foam, thicker, and definitely bridge the ribs with something so the interior screws wouldn't transfer heat or cold to the interior. I've also seen some fasteners that have plastic caps/covers made onto them.

We spent a night in the mid 20s boon docking with a little propane heat to assist, and cracked open roof vent and cracked open windows. Had a fair amount of condensation on the interior metal fasteners, more than likely due to breathing and the moisture content of propane combustion. Another surprise that night was how cold plywood floor got! Wind steady blowing under the trailer really created a heat sink situation on the floor. We later simply bought one of those commercial vinyl/carpet mats just about the right size to cover the entire trailer floor except a couple inches on each side, and it really made a difference. BTW, this is the only time we ever had a sweating issue, and it really wasn't a problem, just an interesting phenomenon.

Last Fourth of July near Calhoun, GA, we camped with friends who brought tents. We purposely didn't bring the A/C unit as a courtesy, and ran just the Fantastic Vent fan. It was ok, but I could tell the roof insulation was struggling during the heat of the day, we were also in direct sun all day. I have two E-track brackets attached directly to the roof studs, and they were warm to the touch due to heat transfer from the roof through the fasteners. Lots of folks coat the roof with Kool Seal, I've considered that, but when we install our modular A/C "closet" it has no problem keeping the interior comfortable even on the hottest days.

Back to winter, if we camp with power, a simple ceramic bathroom style space heater works wonders, even on the coldest nights. The next off-grid step for me would be one of the Dickinson propane marine heaters some have installed on here. Pricey, but really a great unit and solution for most of us.

So don't sweat it, but do insulate with something! I was ready to get it done and get going. The few things I've learned and would "do over" really haven't been enough of an issue to go back and fix it.
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Re: 1in insulation enough?

Postby Esteban » Sun Apr 02, 2017 1:27 pm

The R values of different kinds of rigid foam insulation boards vary considerably. I'm using Polyisocyanurate insulation board for my teardrop because it has the highest R value per inch - R-6 to R-6.5 per inch.

greenbuildingadvisor.com/green-basics/rigid-foam-insulation has helpful descriptions of different kinds of foam board. I copied and rearranged the information to make it easier to post and read it.

EXPANDED POLYSTYRENE
Expanded Polystyrene is least expensive of the rigid foams
EPS is cheap and effective
EPS is the least expensive and most vapor-permeable of the three types of rigid foam.
One inch of EPS has a permeance of 2.0 to 5.8 perms, making it a semi-permeable material.
R-value: 3.6 to 4.2 per in., depending on density

EXTRUDED POLYSTYRENE
XPS is versatile, tough, and waterproof
Because of its high compressive strength and water resistance, XPS is often used below grade to insulate slabs and foundation walls.
One inch of XPS has a permeance of 1.1, while 2 inches have a permeance of 0.55, making XPS a semi-impermeable material.
R-value: R-5 per in.

POLYISOCYANURATE
Polyisocyanurate has the highest R-value of the rigid foams
Polyiso has a higher R-value
Polyiso doesn't use ozone-depleting blowing agents; it uses pentane.
Because it can absorb water, polyiso is not recommended for use under slabs or on the exterior of foundation walls. The foil facing, however, makes it an excellent exterior drainage plane for above-grade walls, as long as seams are taped.
R-value: R-6 to R-6.5 per in. (lower in cold temperatures)

Read more: http://www.greenbuildingadvisor.com/gre ... z4d7NowX1n




If I was insulating a Cargo Trailer I'd screw wood 1x2 boards horizontally (offset 90 degrees from the metal ribs) to the cargo trailers metal ribs to reduce conductive heat loss. Then fill the voids with polyiso rigid foam boards. Then finish the interior by attaching 1/8" or 1/4" plywood to the offset 1x2s in walls and ceiling.
Steve - SLO, CA
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Re: 1in insulation enough?

Postby Iconfabul8 » Sun Apr 02, 2017 5:48 pm

My concern/hesitation with the horizontal 1x2 method would be the diminished lateral strength that many trailer companies rely on the inside boards to perform. It may not be a significant loss of strength, but there are a lot less screws into the uprights with this method.
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Re: 1in insulation enough?

Postby dancam » Thu Apr 06, 2017 1:25 pm

Will you be paying for the electricity for the heat or not? How much will you be using this when its coldish?
Ive tented in 35f before and its not bad but i wouodnt want to do it for a week or something.
If you dont pay based on electricity consumption then 1inch is enough. If you do it depends how much youll use the heater as to whats worthwhile. anything more than 2in probably wouldnt be worth it.
Carpet on the floor.

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Re: 1in insulation enough?

Postby hankaye » Fri Apr 07, 2017 9:31 am

Iconfabul8, Howdy;

Iconfabul8 wrote:My concern/hesitation with the horizontal 1x2 method would be the diminished lateral strength that many trailer companies rely on the inside boards to perform. It may not be a significant loss of strength, but there are a lot less screws into the uprights with this method.


Your statement above surprises me. Even if you are using the horizontal 1X2's and then re-covering them with the plywood the
'anti-racking' ability is still there. Personal opinion is that it should be just as if not stronger then before.

If I were to do it I'd use either some 1/2" or 3/8" plywood cut into 4" strips instead of the 1X2's. Cuts down on the loss of interior
space. There's not that much to begin with.

hank
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Re: 1in insulation enough?

Postby McDave » Fri Apr 07, 2017 3:51 pm

+1, What Hank just said.
In my experience with 6 x 12 Pace, It is not possible to say the interior panels were in anyway a structural element, or even a cosmetic element. This was a random, mish mash of scraps stapled into a patchwork of odd shapes and dimensions with no clear pattern or spacing for fasteners, many of which missed the studs anyways. I can not accept that there was any purpose intentionally engineered, but it did hide the multitude of sins lurking behind. And possibly was intended to discourage items placed in cargo area from damaging the outer skin from the inside, that is all. Period. Mine was NOT plywood, 1/8" (or less) rough panelling. I would estimate 2000-3000 staples, probably more. No way was that drawn up for load bearing or shear strength. Almost anything or nothing would be an improvement. Unless and until I see a engineering drawing reference to that mess being a structural element, it is not.

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Re: 1in insulation enough?

Postby Hader » Sat Apr 08, 2017 11:41 am

In reference to "Lateral Strength":

All dealers that I talked to about ordering a trailer with no wall panels, told me that the builders would not do that because of 'Strength/Warranty' issues.
The more I thought about it, the more convinced I was that was nonsense. I think they were just too lazy to pick up the phone and ask the builder.
When we picked our trailer from Lark's plant, I asked, and was told that they build them for others with no issues as far as strength. The foreman was not sure how that would effect the Warranty.

I re-purposed all of the 3/8" ply that came with our trailer, and used 0.196" luan for wall panel.
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Re: 1in insulation enough?

Postby hankaye » Sun Apr 09, 2017 9:07 am

Howdy All;

Got to admit that I I tend to think back to my years as an aircraft mechanic. Most
of your basic non pressurized Military aircraft have the basic framework then the
'outer skin' which is the same basic 0.032" aluminum 'skin' that is used for our CTCs
and those things fly!

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