insulation

[Mark519]

Hello,
I am still in the design phase of a cargo camper. I have read the insulation topics and would like follow up with some questions for the experts!

I am assuming that AC and heating will be necessary, but would like to have enough insulation to quickly cool down on the hottest days, and get it warm on the coldest.

Due to the thermal conduction of the metal skin and ribs, it seems that placing insulation of any type inside the wall is not going to be that effective. The 3/8 plywood interior does provide a thermal break although not that much R value. It seems that gluing a 1/2" layer of foam board over the plywood would be much better than putting it inside the wall. (The box within a box idea). A thin layer of wood paneling (or whatever) would then be glued to the foam board. Of course this costs 1" of interior space which could be a problem for some.

If the insulation in the void is really helpful, then I like the idea of spray foam instead of cutting sheets. There are companies that do this for homes by drilling holes in the top of each wall void. The foam is then squirted down inside the wall. See retrofoam.com for a video of what I am talking about. Obviously the expanding pressure is low because a product like Great Stuff might expand sheetrock, and certainly puff out aluminum skin. One big advantage of doing this would be extra rigidity to the skin against bumps, etc. Compare to the cost of going to a .040 or .050 skin.

As far as the ceiling, it seems cutting the foam board and placing in between the ribs would not be as effective as placing it completely under them and leaving a void between them. Then attach furring strips for mounting luan.

[kstephenson]

I used foam insulation board between the ribs on both the walls and ceiling. After that I covered with paneling. I have used my camper in both cold weather and extreme hot weather. And it does great. What type of heating and AC do you plan to use?

[Mark519]

I am thinking of going with a Carrier roof top AC because I think they are the best, but would welcome other opinions. I bought a Webasto AirTop ST off ebay for $420. It was a great buy, although I need the muffler. If you aren't familiar with Webasto/Espar, they are very small efficient diesel heaters with a low wattage DC draw (and some burn gasoline). But they are expensive new! Plus I have this dislike of propane.

[CurtMarsh]

You might be interested in the spray foam threads that are on the Airstream Forums. Pretty much everyone has abandoned spray foam on them due to the spray crumbling due to the motion inherent in mobile installations. Also, The use of a rooftop air on a small space such as a ct might lead to short cycling of the unit and performance issues. It only takes 5 to 6 thousand btus to cool these small spaces not the 135000 that a roof ac produces. Curt

[Mark519]

I didn't know about the crumbling issue. Although I did wonder about outgassing. I am looking at the 7x16 size, in Southern states. So I assumed 13.5K would be necessary but I will certainly look at that more carefully now. My heater may cycle too much also for mild cold also. Maybe I shouldn't worry too much about the best insulation!

[Pyrofish]

I'm still working on mine, so I can only tell you what I have planned, not actual experience

In the roof, I have added 1" aluminum square tubing (screen room aluminum type stuff) to the underside of the 1" steel frame. This gives me 2" of space, which I plan to fill with 2" polystyrene insulation panels. To hold them up, I plan to use strips of 1/2" plywood cut to 3" wide. I figure the plywood is light, and strong. 5mm plywood over that (sometimes called Luan).

For the walls, since the steel members are spaced on ~16" centers in the walls, I'm using 2"x1" Aluminum channel (again screen room stuff) to attach to every other steel frame member. That will give me 3" thick walls, with 2" of easy install foam. The outer 1" by the trailer skin will remain open air.

To tie the wall aluminum frames together, I plan to use 1x4's where I don't plan to attach anything, and 1' x 8' pieces of 3/4" plywood where I will attach things. Paneling over all of that.

Waiting on my AC parts now. I didn't know the used one I bought would need a controller, a thermostat, and a grill....

I camp in 90F temps all of the time, so I'm thinking the 13500 BTU unit will be ok with my monstrosity of a Toy-cave.

[pilgrim]

I did both. In between the outer skin and the 1/4" plywood I was able to use 1" insulation. I stuffed it in between the studs and then since mine were kind of a u type channel I stuffed some in there also. Then I taped over the studs with aluminum tape and put the plywood back on. From there I added another 1/2" insulation but this time I used the "R" board that has the thin fiberglass layer on the outsides. The I applied my final paneling over that.

For the roof I did somewhat the same. The difference is that I used lathe going the length of the trailer. 1 1/2" in between the ribs and then 3/4" between the lathe. I ran the opposite direction to get better coverage.

I know it was kind of a overkill but then I live in NW Montana. Just the opposite problem everyone in the South has, I needed to try to get as much heat to stay in as possible!

Pilgrim

[8ball_99]

The rigid foam between the studs does more then you think it would considering the metal studs. I used a layer of that bubble foil insulation then a layer of 3/4 in the wall. Then it has 3/8" plywood then on top of that paneling. On the ceiling I did the same with the insulation but then I also added strips of 1/2" plywood on the studs and put a 1/2" layer of foam between strips. Then a layer of luan. I wanted the extra layer ontop of the studs in the roof since thats where you gain and loose most of the heat. If you can afford to loose the space inside the box inside of a box is the best way to do it..

As far as the roof top AC I have a 9200 coleman cub on mine. It worked GREAT on my 6x14 trailer.. I sold that trailer and moved the AC to my current 7'x24'. It works Ok on my current trailer. It takes several hours to cool the trailer down if you cut it on in the middle of the day with 90+ temps.. It has NP keeping the trailer cool once everything is cooled off. Even opening closing the door, ect. Coleman now sells a 12k unit that my honda 2000i will run so I'll probably upgrade to it at some point.. I would say a coleman cub would be plenty for a 7x16. I could cool my 6x14 off in about thirty mins to an hour. It also would turn it into a meat locker if you didn't set the thermostat...

[8ball_99]

BTW If your close to North Alabama and are looking for a one year old coleman cub I know a guy lol...

[Mark519]

8Ball, I like your 24 footer. It is a lot like what I am thinking about. I am reading the airstream forum right now.

[kstephenson]

I am using a window AC unit 5000 btu. Along with the foam board insulation in the walls and ceiling. It cools down in less that 30 minutes and so far have been able to cool down inside temp to 67 degrees with an outside temp of 98 degrees with 57 percent humidity.
Total cost of AC unit was 92.00

[Kyle1911]

Our 24' V-nose has 1" polyiso in the walls and ceiling. Floor is not insulated. We haven't done extreme camping with it, but I have a 13.5k ac in the ceiling, that will cool that space in about one hour from 100 to 75ish. I do have an airflow issue to resolve, to get cold air up to the bedroom in front, but overall, the AC works well. I would not want a smaller unit on this size trailer. As for heating, we have camped down to about 38 degrees, and the 1500w wall heater keeps it nice and toasty. It takes a lot less to heat than to cool, it seems. The transfer of either cold or hot through the metal studs is noticeable, for sure, but hasn't caused any problems yet. We live in the high desert of central Washington state, so humidity here is pretty low, <50% most of the year. If we were in a more humid climate, I might have added insulation over the metal studs, also. I did use vapor barrier over the Iso insulation. I "Saved" a few bucks per sheet, and got the fiberglass covered stuff, instead of the foil faced. My advice to you, if you use the Iso, GET the foil faced stuff! I looked like a monkey trying to procreate with an octopus for several days, trying to install 1mil plastic vapor barrier in a breeze. My kids learned many cool new words for the school lunchroom. In addition, the fiberglass faced stuff is brutal for itchiness. It's more like handling rockwool than normal batt insulation. Not fun. The foil faced Iso gets 3 birds stoned at once. Decent vapor barrier, no itchiness, and some measure of thermal reflection. Regards, Kyle