7x16 conversion

[hberg]

I have a 7x16 continental cargo trailer that I am thinking about converting. I came across this forum, and wow! what a bunch of great ideas. One of the primary uses will be winter-hunting and taking my wife and three kids skiing to ski areas in the PNW. It usually doesn't get super cold around here, but would like to prepare for down to 0 or so. Obviosly we have warm sleeping bags, but it would be nice of the trailer would retain heat overnight.

So my first question is about insulation. It looks like most people have taken off the interior panels and installed 1.5" foam board R7 or so insulation between the studs. How well does that work in cold temps? Glued or taped or just hung? And did you tape the seams?

I was thinking about placing an additional layer on top of the metal frames, and just using longer screws to put the plywood back on, like a SIP. That could double the R value to about 14, and eliminate (lessen) heat transfer through the metal, at the cost of 3" of interior space. Seems worth it to me.

I also am considering foam spray particularly for the underside, but it could be used all the way around.

Another option is some type of foil backed bubble wrap (reflectex) as a layer in additon to or in loiu of one of the foam board.

Good ideas, or overkill? I guess I would rather pay for insulation than heat.
I would appreciate any thoughts or experience with winter camping in your converted cargo trailer.

[edcasey]

Looks like you put a lot of thought into this. Like you said, most of us are using rigid foam insulation. It sounds like you're looking to use your camper in colder weather than most of us. Your idea of doubling the installation and covering the studs is interesting. This would help eliminate conduction by the wall studs and certainly help with condensation. I actually did something similar with our house. I bought an old cape and gutted it. I built additional walls in front of the existing exterior walls and offset the studs. Like your plan, this doubled the insulation and now none of the exterior wall studs contact the drywall eliminating conduction. It works so well we heat the entire house with a standard water heater.

I take my conversion up to Augusta Maine every year for Christmas and the temperature frequently gets into the single digits. My trailer was made with 1" X 2" boxed steel so the insulation is 1" thick. I glued the insulation to the exterior skin and aluminum roof with a very strong contact adhesive and then glued luan to the insulation with the same adhesive. I didn't install any insulation in the floor but I did elevate the bed so warm air goes under it and keeps us warm.

We use an Atwood 7912 furnace (12,000 BTU's) that I got slightly used. The 7900 series are excellent furnace but if I was to buy a new one I would get a 16,000 or 18,000 BTU unit. The price is the same or slightly more than the 12,000 but it wouldn't have to run as long when it cycles on and would warm up quicker when it's first turned on.

I only installed one window which is near the foot of the bed. It's dual pane but you can still feel the cold when you put your hand near it. We made an insulated cover to place over it. I also installed a bulkhead wall in front of the rear doors. It is actually a two inch thick laminated wall from a camper that was totaled. It is foam insulation glued between fiberglass and luan with no wall studs.

The whole setup works fairly well. I wouldn't want to live in it all season but for one long weekend a year it's fine. The floor is very cold and the walls are cold to the touch. We definitely don't want to be in contact with the walls when we're sleeping. The furnace keeps us nicely warm and I have the thermostat anticipator set to cycle the furnace with just a one degree drop in temperature. This keeps the temperature constant but the furnace does cycle on often. I think if I was building it for 0 degree weather like you are I would want more insulation and an insulated floor.

[hberg]

Thanks for your response. That was helpful.

In my research I just came across these guys: www.insulationdepot.com. They sell used foam board insulation, with warehouses throughout the country. Anyone have any experience? They have 3" thick boards, so my latest thinking is to carve out just enough to go around the studs, which will leave at least 1.5 inches of insulation between the stud and the wall, then screw the plywood back on over the top, in the original holes.

Still trying to work on the floor insulation.

Does anyone know exactly how thick the steel framing is? Or if they are a Z, or [ frame or tubular? Or if there is any type of cross bracing? I haven't taken the 1/4" plywood off yet.

[bobhenry]

We are idiots we are the 1st group out in January ( for bragging rights).
Indiana in the 2nd week of January is generally the coldest weather we see. In 08 we experienced -15 wind chill 09 was a balmy 7 degrees and a constant 30 - 35 MPH wind.

SO !

When I built "THE BARN " I added 2 layers of 3/4 foam board directly on the floor inside then covered with a layer of 7/16 osb as a sub floor. I carpeted the sleeping area and installed laminate flooring in the rear entry and galley area directly over the osb sub floor. Yes I lost 2" + in height but I feel it was a good trade off. It was fast it was simple and it is out of the elements.

here is the bare floor



here you can see the foam on the floor




here you san see the sandwich


and the laminate in the doorway

[Trackstriper]

hberg,

I too am working on a cargo conversion and will be dealing with the insulation soon. Let me share some of my thoughts about your ideas.

My trailer was made by Pace and has Z-section studs for the walls, I would think about 18-16 ga. I don't know what Continental Cargo uses but most of these trailers are built very competitively...they can't upgrade the materials too much, unless you buy a really nice rig like Prem has... Featherlite. If you talk with the dealer or factory they will get probably get kind of bunched up if you tell them you're going to even temporarily remove the factory plywood. On the cheaper trailers it's actually designed (or so they claim) as a load bearing structure. The Pace factory guy admonished me when I took my trailer to them, sans interior wall ply, for some warranty work. Said I'd need to make sure the trailer was leveled and squared (body wise) before I put new plywood back in. I believe he was serious as he was a really nice guy and was wasn't trying to give me a hard time, just a heads up. Of course they are considering a trailer designed to have a loaded weight of 3500# or so, and some dolt will load it to 5000# and drive down the road. Our conversions should be relatively easy on the framework.

That said, I think it would be wise to fasten your wall panels firmly to the studs rather than having some rigid foam as a barrier between the ply and the stud. You'd never get the screws tight anyway as the foam would compress until things got ugly. You could "fir out" the metal stud, however, with some wood that would be firmly fixed (construction adhesive) to the metal. Your interior plywood could then be rigidly screwed through the wood and stud. The wood strip would act somewhat as a thermal barrier, at least better than the metal stud. A "Z" section stud should be preferable to a square tube or a hat section with regard to acting as a thermal bridge.

If you could get the bottom of the floor sprayed with foam that might be cool as it would do a lot of sealing and could be put in three inches thick. If you watch the spray foam installations on Youtube you'll realize that it's not exactly precise. But under a trailer it wouldn't have to be too pretty. Might work on the side walls and roof too but there would need to be a lot of trimming to get it flat enough to put the plywood back over it cleanly. Seemed like someone else on the forum was going to try it but I don't recall if it ever happened.

Edcasey probably took a hit thermally by not doing the floor. Plywood has some R-value but it's not much, about 1.0 for 3/4" ply. I'm planning on using 2" rigid, extruded polystyrene (pink or blue board) under the floor and in the ceiling. I've already purchased some foil-faced 3/4" polyisocyanurate panels for the walls as that seems like all that would fit well. I couldn't readily find 1" rigid board here in Atlanta.

The foil/bubble wrap has been discussed on the forum and my instinct is that while it does insulate, the advertised R-values are pipe dreams....it probably does quite well stapled to the bottom of roof rafters.

Bruce

[hberg]

Track- thank you I hadn't thought of that. I called Continental and confirmed that the plywood does have a structural component, primarily fore and aft stability. He suggested I could use a 1x4 as framing to hold it all in place, but didn't think it would be as good as the plywood. That is what they did with the ceiling, I noticed. So the upshot is that the plywood should be attached directly to the metal framework.

Also Continental uses hat shaped framework that is 1.5" thick.

So that leaves placing 1.5" insulation between the frames, and placing auxilary insulation if desired attached to the interior side of the plywood, with some sort of facing as the final interior wall.

This scenario actually sounds like the perfect application for foil backed bubbles if you can believe their literature. They maintain that in metal buildings with 3/4 inch air space reflectix is good for R6.8. But as others have said, I am a little skeptical.

Still waiting to hear from my SIP panel guy to see what he can do- exterior wall, foam, plywood, foam, interior wall (wall board) all glued and pressed together seems pretty solid.

I thought about above the floor, but am working with limited height, and still want to use it as a cargo trailer. I am concerned about trapping moisture with DIY foam board installation.

Thanks again for the help.

[Curtis in Texas]

Subscribed!

I have a 16 X 7 Continental Cargo Trailer too.
I'm hoping to find time after the first of the year to convert it to a better camper.

Curtis in Texas

[Trackstriper]

I am concerned about trapping moisture with DIY foam board installation.

I am too. But where do you think the water/moisture might get trapped. Is the primary concern trapping between the plywood and the foam where the wood will rot or between the foam and the steel framework where rust might come in, or both.

I will insulate the bottom with 2" rigid. My floor plywood is currently out while I have been rearranging the crossmembers to put them where I want them for attachment and structural reasons. I'm going to redo the floor in 1/2" MDO as it is lighter and much more water resistant. When removing the old, almost-painted 3/4" cheesy-ply I weighed each piece, a total of 168# in my 6x12. I did add one crossmember and tightened up the spacing of the others, seeming overkill but I needed to have the crossmembers in the correct location for floor seams and to be able to support a gray water tank just forward of the axle.

I'm noodling around right now about installing the foam between the crossmembers before I put the new floor in. I think I can cut the foam slightly smaller and glue it in with the insulating foam-in-a can stuff, really seal it up. Maybe tape the seams top and bottom with 2" aluminum duct tape.

I'm also thinking about doing walls with 3/4" + 3/4" rigid board as I have some already, and furring out as mentioned above. Recent posts on the forum seem to indicate that our cargo trailers are pretty bad about loosing heat with all of the aluminum and steel.

Could use some feedback about the moisture issues.

Bruce

[hberg]

I got the insulation from insulation depot. Very easy-used the trailer to pick it up at the warehouse. $315 for a 4'x4'x8' pallet. I was able to split the order, so I got 1" and 3" "Energy 3" polyisocyanuate from Johns Manville. Surplus, never been used, saved from a landfill. It has a fiberglass/felt backing on both sides.

I installed the 1" in the walls, pretty straightforward, by taking off the interior walls and placing the insulation between. I may still add the remaining 1" to the interior as another layer, with a wallboard final wall but would like to test it out without that first.

I put 3" in the ceiling by cutting the 4' boards into two 24 inch, then trimming out enough so that the roof supports would fit. With some difficulty I then screwed in 2 sheets of 1/4 plywood to the roof supports to hold it all up for the 16 foot length. I took some pictures if I get around to posting them.

I plan on doing the same under the floor, and hold it all in with adhesive, screws and some waterproof plastic wallboard I got at home depot.

So I will end up with 3" polyisocyanuate in the ceiling and floor and at least 1" in the wall, and probably go up to 2". Also, I will make a 3" false wall over the rear barndoors for winter use.

That is where I am now, thanks for the help.

[BC Dave]

On a 6X10 Interstate with a 6'-2" overheight roof.

I was intrested in getting the best insulating value I could.

On the walls I used was r 14 batten insulation squished under 1X3" SPF strapping screwed to the metal hat studs;

on the roof & doors I used 1" high density pink foam and

on the floor; glued to the under outside; I used 1.5 " foam.

Interior was covered with 3/8" 4 ply marine grade fir; and on ther bottom 21" I used 2X3 strapping with 1/2" ply as a kick board and bottom rail. Even with this insulation the cold and condensation / frost still shows where the metal frame is and on any screw head on below 50 .... oh ...and I have not noticed the 3" of lost space on the inside of the trailer due to added strapping.

Let us know what you used and how it worked.

Cheers Dave