Insulating a Cargo Trailer

[Day Dreamer]

Hello All!! It's been a while since I've been here. Got hit hard by the covid shutdown killing my business, losing jobs due to layoff etc. and divorce (lost house). Now finally getting back on track.

I had been planning on "hitting the road" as a back up plan right before covid (which is now my forever back up plan which is good to have). Experienced camper and backpacker so easy adjustment. Way easier than thru hiking the AT. haha

So I bought this 5x8 cargo trailer. My plan is to make it mobile business and tiny camper combo until I retire (I'm 58 but probably like many here some life events kinda screwed me for "lush retirement"). Depending on how the stock market shakes out now I have 5-10 years of work left.

I have the trailer gutted and I am getting ready to insulate with -

Johns Manville R- 6, 1-in x 4-ft x 8-ft AP Foil Faced Polyisocyanurate Board Insulation​

My question is - Should I install foil out or in? I'm getting conflicting info. I will be using it mostly spring through fall.

Thank you!

 

[bullfrog !]

For me ( I am no expert ) it would depend on the temperatures I would be in, what type of heat/cooling I would be using and what type of ventilation. Is the foil meant to be a vapor barrier? Will there be a ventilated air space between the insulation and the trailer wall which I assume is metal? Condensation would be my main concern. In such a small trailer any heat source is going to be almost too much! If you are using a dry ventilated heat source you probably won’t even need insulation, in fact you may need more ventilation to prevent condensation from your body heat. In summer unless you have access to grid power for AC you will need lots of cross flow ventilation and external shade (parking in the shade really helps) like a shade structure or elevated roof rack with maybe a reflex or Mylar reflective surface will help. People have used a misting system as well but the outside surface of the trailer can be damaged by deposits left by the water deposits evaporating but in dry climates it can lower the inside temperatures at least 10 degrees.

 

[Day Dreamer]

For me ( I am no expert ) it would depend on the temperatures I would be in, what type of heat/cooling I would be using and what type of ventilation. Is the foil meant to be a vapor barrier? Will there be a ventilated air space between the insulation and the trailer wall which I assume is metal? Condensation would be my main concern. In such a small trailer any heat source is going to be almost too much! If you are using a dry ventilated heat source you probably won’t even need insulation, in fact you may need more ventilation to prevent condensation from your body heat. In summer unless you have access to grid power for AC you will need lots of cross flow ventilation and external shade (parking in the shade really helps) like a shade structure or elevated roof rack with maybe a reflex or Mylar reflective surface will help. People have used a misting system as well but the outside surface of the trailer can be damaged by deposits left by the water deposits evaporating but in dry climates it can lower the inside temperatures at least 10 degrees.

Thanks for the reply! It will be used mostly in the spring to fall so warm temps. I plan on starting out with A/C possibly an RV unit. No heat for now.

I don't plan on gluing it to the inside but there will only be a very small air gap if any between the trailer and insulation.

Right now I'm living in PA so it's not a very dry climate and my trips will be east coast. My travels will eventually include out west (BLM land) and Florida.

Ventilation won't be an issue as I will be installing a Fantastic fan, two small windows and a small side door.

Down the road (no pun LOL) I will be adding solar as well.

 

[bullfrog !]

The foil side is usually facing the side you want the heat to stay on. Having a ventilated air space between the metal surface of the trailer and the foil would be very effective in my opinion but take up a lot of space. Really to me the foil if you are putting it directly against the metal, is a waste. Most buildings with vinyl siding face the foil towards the interior as it makes heating the inside more effective and serves as a vapor barrier. With a roof top 13,000 btu AC in such a small space won’t need much in the way of insulation. Plain ridged foam installed so there are few thermal bridges ( transfer of heat thru metal ribs ) by using foam tape over then covered with thin plywood or paneling in my opinion will be plenty. Window shade material or temporary awnings will help during the day as well. Again I ain’t no expert! If solar is mounted on the roof use an elevated rack as the panels create a lot of heat underneath them in the first couple of inches and won’t work as well without air flow in that area. Also bright white exterior and white insulating roof coatings really work in extremely sunny areas. If you are not going to glue insulation make sure it fits tightly as it will deteriorate as it vibrates going down the road. Again this is only my opinion and I usually am in the dry Southwest which does get cold sometimes in the winter so maybe if you are going to cover the insulation with interior panels and are using foil backed insulation with a huge RV roof top Ac consider facing it in.

 

[maki2]

In a trailer some times you will be trying to keep heat in and other times you will be trying to keep it out. So that means it is pretty much irrelevant as to what direction you face it. Plus in order for reflective heat to work it can’t be up against other materials. So no matter which way you face that reflective surface it is going to do a whole lot of nothing. The foam is the insulator in these situations.

But if you are applying tape to it then choose to tape to the plain side as the micro thin aluminum can be peeled off and stick to the adhesive so that means the tape might come loose.