First offroad trailer build

[OrangePower]

Hi

I must say I`m getting addicted in planning my first trailer build. I would like to build offroad trailer 5x10 and inner height arround 55". It must not be heavier then 750kg or 1650pounds fully equiped.

Since we need registration here in eu and for DIY trailer you need A LOT of documentation I started drawing one in Solidworks and making some simulation for choosing correct material and to have calculations for registration office.

In general I know what I want but I have no experience in some areas.

I will use this trailer in hot summer and maybe in some cold snowy winter nights (maybe) in general I think I will not be needing heating or cooling just vents to ventilate sleeping area before sleep.

My first queastion is: insulation

1. is it ok to have on or not, since this leaving area is small

My concern is if I take wood and glue aluminium, metal or plastic plate on it, where condensation will be on cold nights?

I was looking at composite plates but they are expensive so my plan is to make:

- outer shell probably out of metal plate or maybe plastic material that is used on campers (I can order this material in different thicknes (1mm, 2mm....),
- inner shell out of plywood (maybe 1") if there will not be any insulation
- maybe walls out of (from outside to inside) - plastic 2mm thick - plywood 10mm - 20mm insulating panels - 10mm plywood.

I dont need walls to be strong to support it self because I will use metal L profiles on outer side for protection and for monting construction of walls.

What do you prefer for walls when building this kind of trailer?

 

[john61ct]

Insulation is very important if using active heating or cooling off grid to save energy.

Do not allow thermal bridging with metal to the inside.

Very tight sealing of the entire envelope against convection losses, combined with well controlled active ventilation is needed against condensation

especially if burning propane inside.

 

[john61ct]

A-frame should be stronger, and reinforce its attachment points

 

[OrangePower]

Do not allow thermal bridging with metal to the inside.

Not shure If i understand that.
How to avoid that?

 

[Furaites]

Thermal Bridging....Hmmm Think about this you have a panel van, made out of metal....If it is hot outside....then the metal heats up...and when you touch the inside of the van the metal is hot....same when it is cold outside...SO

So you want to make sure that Heat or Cold from the outside does not transfer to the inside of your habitat. You do this by making sure there is adequate insulation between anything that will conduct head or cold from the inside....and the inside wall of your habitat.

So if you have a metal frame of your habitat, you do not want to have that metal frame right against the inside skin of y our habitat. You feel the large gaps between the frame with insulation, and then there should be at least a thin layer over the metal frame before your inner wall.

 

[john61ct]

Very well explained.

If there is any metal allowing a conductive path to the outside, in winter touching it feels colder than the wood panel, it is sucking your thermal energy from your living space and radiating it to the outside, in effect bringing the cold inside.

A thermal infrared camera is a good way to spot such flaws.

The ideal is the same R-value across the whole surface, say using a continuous 2" foam slab under your whole floor board layer but all of it above your structural framing.

Then you could also add foam between/within the framing gaps, but that's just optional extra, not the main insulation.

Of course more effective insulation like that reduces the usable living space, so planning that out in your initial design is important, if the outside width was 62" without insulation, maybe make it 66" instead.

And the 2" is just an example, in a mild climate 1" is enough, but running aircon fulltime boondocking in Arizona, you'd save a lot of money going to 3" or even 4".

 

[jwiereng]

Very tight sealing of the entire envelope against convection losses, combined with well controlled active ventilation is needed against condensation

No leaks, but have lots of excellent venting.

Lots of condensation can come from breathing people

 

[billiebob]

Thermal bridging in a home is important, in a tiny trailer with a metal frame not an issue.

Condensation occurs at the dew point, relative to temperature and humidity, easy to calculate in a stationary home, less so in a trailer. You either seal the entire interior envelope like a refrigerator or make the unit well ventilated. Sealed up tight creates a box to incubate diseases..... google box beds, Scotland, tuberculosis. Do not over think this. Insulation will just reduce heat loss and lower yer propane consumption. But in a 5x10 trailer who cares. you NEED ventilation, do not build an air tight incubator. ps.... air leakage will also leak moisture.

I'm thinking misprint on the interior siding, 1/4" plywood is plenty, 3/8" adds flexibility for hanging fixtures. If your frame is 1" square tube, just fit 1" extruded insulation to fill the voids. Attach the outer skin directly to the steel tube frame. Go look at some commercial retail cargo trailers, they have the most cost effective designs.

AND pick cost effective vs expensive choices.

Pick choices which require no power, forget active ventilation, open a window. Sleep under a winter sleeping bag. rather than turning up a thermostat. Ventilate while you sleep, two open windows, close the windows in the morning, turn up the thermostat. If you get rid of the air you breath and add fresh cool outside air you eliminate condensation and likely sleep way better.

My OSB BOX has no insulation and I always sleep with a door open. One day I'll add a Propex Heater for the mornings.

 

[john61ct]

Yes the **ability** to turn your CFM up to high is important.

However with uncontrolled leakage / convection losses in harsh conditions huge difference between inside and out, you are losing a very high percentage of your monthly heating costs for no purpose.

And to say "thermal bridging in a mobile context is not important" is just insane, literally speechless...