Insulation on Ceiling

[Mountain Cur]

Was wanting to know if anyone does much cold weather camping in their cargo? I'm getting ready to start putting rigid foam board insulation between the ceiling supports then 1/4 paneling over that. A guy I know tells me he has seen several horse trailers insulated like that over the years that would drip condesation real bad from the metal screws screwed into the roof supports. He was recomending screwing some wood strips along the ceiling supports for the inside screws in the paneling to go into. That way inside metal screws would not have direct contact to metal from roof. You guys have any problems like that with these cargo trailers or is it a heavier horse trailer deal? Being the majority of my camping is going to be cold weather camping was wanting to get this right.

[pete42]

I don't have a trailer now but my old scamp would drip because the rivits that held up the cabinets ect went from the outside to the inside.

You used a phrase that is mid-west "Was wanting"
when I used it my friend from NC said how do you "was want" something?
I replied I doesn't know we'ns just do.

[High Desert]

I can't speak directly to this problem with CTs, but I can with horse trailers. They do tend to sweat if they are tightly sealed and with horses loaded can almost rain in the right conditions. But venting them makes a huge difference. Empty I've rarely seen it myself. Semi trailers will also sweat some under certain conditions depending on the load inside them (i.e.-nursury stock). Both are built with somewhat heavier materials thans a light duty CT of course. Uninsulated roofs sweat worse in both types. I guess what I'm getting at is that the presence of living things adds to the effect. I sure some long time CT users can shead more light on the direct subject.

I do like your friends idea even if it adds a little work.

[d30gaijin]

Mountain Cur,

I think you'll see a condensation problem only in cold weather if you're inside your CT without heat, which is why horse trailers experience it in that they're typically not heated and the body heat and moisture (the horses exhalation moisture) the horses give off cause the condensation. If you heat your CT just a bit while you're in it it shouldn't be a problem. I installed the foam board insulation as you're planning to install and used 1/4" Luan plywood to hold it in place. I didn't screw the Luan to the metal frame members, instead I Pop Riveted it in place because I found that easier to do than drill the holes through the Luan into the metal fame and then screw a boat load of screws in place. I used aluminum Pop Rivets that are simple to drill out if need be. Photos are below or you can see my build thread here: http://www.tnttt.com/viewtopic.php?t=38095&postdays=0&postorder=asc&start=0

I live in Idaho and cold weather camp, although not a lot in my CT conversion as of yet in that I am still in the middle of my conversion, but I have experience with cold weather. We did a trip over this past Labor Weekend in the uncompleted CT conversion into some high country and ran into temps in the very low 30's. We took along a very small old electric resistance heater with a fan, and I mean very small, but it does kick butt considering how little the thing is. In the 3am time period it got really cold inside the CT so I turned on the little heater to high with fan at high and within a half hour it nearly ran us out of there, I had to turn it way down. We had no problem with condensation.

We found it necessary to reconfigure the bed arrangement in our CT build (see my build thread above) but got held up due to a bout with Bronchitis but the bed reconfiguration is mostly complete and we'll now be heading out again for a few more camping trips before the snow flies, and they will be cold weather camping trips, as time permits (I won't haul a CT on snow covered roads).

Bottom line, if you heat the inside of your CT conversion while you're in it condensation shouldn't be a problem. Also, crack the roof vent a tad for a wee bit of air flow (no matter how well you think you're sealing/insulating your CT it won't be sealed completely. They just aren't designed to be air tight). Air will come in from the lower frame areas and cracking the roof vent will allow air and moisture to flow out the roof vent.

Don

[Eric K]

Heating the trailer can make the dripping worse!

Apples and oranges here... I lived in a steel sailboat for 4 years. I added insulation throughout, and everywhere that interior air could touch a cold surface there was condensation.

Winter was a challenge when we had two people breathing, along with cooking and washing moisture. Diesel stove and lots of air flow helped, but didn't stop the symptoms.

The only "fix" was vapor barrier between the hot moist air, and any cold surface fastener.

Eric K

[d30gaijin]

Heating the trailer can make the dripping worse!

Apples and oranges here... I lived in a steel sailboat for 4 years. I added insulation throughout, and everywhere that interior air could touch a cold surface there was condensation.

Winter was a challenge when we had two people breathing, along with cooking and washing moisture. Diesel stove and lots of air flow helped, but didn't stop the symptoms.

The only "fix" was vapor barrier between the hot moist air, and any cold surface fastener.

Eric K

Erik,

I don't doubt your experiences at all but since, as you suggest, we may be talking apples and oranges, then perhaps consideration should be given to what we're really talking about i.e., boats vs. cargo trailers? Size? How cold? Wet cold? Dry cold? (humidity) Internal temperatures? External temperatures? Number of people crammed into the space provided and their moisture offing? Washing dishes? Washing clothing? Showers/bathing in confined spaces? I can envision whole different scenarios with a steel hulled boat on a lake or ocean than an aluminum skinned and foam board insulated cargo trailer with very little offing of moisture other than breathing of occupants.

As you note, heat (does it really matter whether it is was diesel heat or some other form of heat?) and ventilation helped so I don't see a huge difference from what I have said based on my experience.

Still, your point about moisture barrier is well taken. Would you consider that as a plastic film moisture barrier between the insulation and trailer interior walls or an insulation barrier, as the earlier poster suggested, by screwing wood frame pieces to the metal cargo trailer metal frame and then screwing the 1/4" ply to the wood as a moisture barrier? I'm curious to know if a "Vapor Barrier" of thin plastic is necessary when using foam board insulation as it is when using fiberglass insulation?

Thanks,
Don

[hberg]

I can speak to this. The short answer is yes there can be condensation, and your friends idea may be a good one.

I have a 7x16 that we use mostly for ski trips for 2 adults and 3 kids under 6. I insultated the ceiling with 3" polyisocyanurate cutting out space for the ceiling joists so even at the joist there was 1.5" of insulation. Covered with 1/4" plywood and screwed into the joist.

We have two sources of heat; an electric space heater, and a Big Buddy propane heater. Both run only briefly evening and in am.

In our experience, using the electric heat was dry and we did not get any condensation. Using the Big Buddy we would get condensation on the cieling screws...not bad, but noticable. It is possible that was more due to atmospheric conditions, wetness of kids, etc than heat source, but the Big Buddy does produce water vapor.

For this winter I am considering placing some material on the screw heat (hex) to prevent a recurrence. (Ideas?) Also, more active ventilation (fans) would help.

[Eric K]

If the screws are into wood, and not into the metal ribs, then the screws will not be cold enough to condense moisture out of the air. If the screws get cold to the touch they will need to be covered. Plastic caps, putty, or even wax will work for this purpose.

My boat was 36 feet on deck, less than 20 feet in the cabin. This is a little larger than a TTT, but the principles are the same. Cold exposed parts will collect moisture and can even drip on you, while you are just there minding your own business.

The Diesel stove is like a wood stove in that it uses an external chimney to remove all combustion gasses (moisture) and also draws more air out of the space allowing for dryer, fresh air to enter. As anyone who has used one for heat in a house knows, a wood stove will tend to remove a lot of moisture from the air.

Lots of ventilation and a CONTINUOUS insulating barrier/ vapor barrier, can change a miserable damp interior into a cosy, warm, inviting get-away!

One cold weekend camping will help you find the spots that could use more attention.

Bu all means insulate, just watch the details.


Eric K

[Mountain Cur]

Thanks for all the replies. Planning on getting started tomarrow.

[weeeee]

Just so I am clear on this.

The vapor barrier should go up first and contact the outer skin and joists etc, then insulation and some sort of wall covering, paneling plywood etc.

[GPW]

Apologies , I don't "get it" ... You're putting a VB between the AL and the insulation , to protect from the moisture INSIDE the trailer ???

[Engineer Guy]

Vapor Barriers are always put on the living space-side of Insulation, regardless of whether that volume is a TD or a House. This standard practice keeps moisture [from Cooking, Bath/Hot Water use or simply breathing] from condensing in-Wall and rotting/molding Wall interiors. This is why 'House Wrap'-type material, placed under Sheathing on the exterior of Wall Framing, lets moisture escape while cutting down Wind infiltration. While Desert cold Camping a few weeks in the TD-sized space of my SUV, my Dog and I certainly exhaled enough moisture to condense out on single pane Windows. Even with the Sunroof cracked open...

http://nstar.apogee.net/res/reinvap.asp

One Poster here wisely put his screws into Wood furring strips so they don't contact cold exterior metal directly, and drip condensed interior humidity. Isolating interior and exterior surfaces, including screws, is a smart construction method to use, if possible. My commercial Travel Trailer has a dripping, single-pane Vent from this condensing effect, inevitable at the warm surface -> cold surface interface. I've not bothered with inserting a fitted piece of rigid Insulation. That Trailer is unused right now.

In most areas, Vapor Barriers - like that on faced Fiberglass Insulation - still go on the interior side [just under the Drywall]. Heat rises, so House Ceiling Insulation is typically ~2x the R value of Wall Insulation in an ideal World... TDs are simply small House volumes, more-readily heated by Bodies and Lights, etc.. This all has been figured out before, as posted on a number of House Building or Insulation Web pages.

[weeeee]

Thanks, I am clear on the vapor barrier. I was concerned about about metal ribs contacting the interior sheathing, so I will probably consider using furring strips or similar to buffer that.

[GPW]

Thanks EG !!!

[BC Dave]

... done lots of cold weather camping to -20 C.

Heat helps to minimise interior sweatting; I use a boat propane heater that has served me very well. Its a sealed unit so all intake and exaust is to the exterior.

CT Insulation / finish - The ceiling is insulated 1" ridged blue foam insulation (or was it 1/2 in; whatever max I could insall betwen the ribs; I didnt want to loose any head height). It has worked well; I would have installed thicker but I didnt want to loose any head height. The finished material was 1/4 good one side exterior sheathing ply; sealed with polyurithane; screwed in place with self tapping wide and heavy headed galvanized screws. This is covered with finished strips of oak trim again sealed with poly -U. Walls have 4" fiberglass batten insulation with 3/4" & 2X3 firring strips with 3/8" & 1/2" ply.

I notice minimal sweatting as the screws have a second layer of oak trim on top; also the firring strips offset direct screw contact and the poly -U acts as a vapour barrier; as suggested above. I notice the most sweattingin the interor around doors where the metal is still exposed ... check my pics for a better description.