New here with a question about insulation

Converting Cargo Trailers into TTTs

New here with a question about insulation

Postby ISOTNT » Mon Jan 25, 2021 9:21 am

Hello! I am new here with a question about insulating our new 8x20 cargo trailer for use as a toy hauler for dirt biking.

I am currently installing poly-iso 1” between the ceiling bows and plan to put furring strips below that and another ½” of XPS between the furring strips and then install the ceiling laun.

I am fighting to remove the side plywood panels now and have only 2 off so far (evil screw nails) and plan to do another one or two each day. Then, I am planning 1”poly-iso between the studs and foil tape/can foam etc.

That said, here is where I am not entirely sure how to move forward – should I use furring strips on the sides? It would seem that screwing the plywood right back on those metal studs would create one heck of a thermal bridge. I am in Texas and those sides are going to get real hot, but I don’t see many builds where people use furring strips on the sides and have mostly only seen it done on the roof. Any reason for that? Is there something I am overlooking?
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Re: New here with a question about insulation

Postby foxontherun » Mon Jan 25, 2021 12:09 pm

Welcome to the forum. I live in TN so familiar with how hot it can get though I am sure it gets even hotter in TX. I wanted my build to be a four season trailer as we plan to full time it. This is what I did on my build.

First layer is 1" between the wall framing members and taped off with aluminum tape
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Second insulation layer is 1/2" ran perpendicular to that first 1" layer. I also added the 1" (true 1") framing (white board in pic) parallel with floor to use for final wall covering support..
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Third insulation layer I added 1/2" plywood strips (1-1/2" wide) fastened thru the second layer insulation into the wall framing members with 1-1/2" self tapping bolts. I used a forstner bit to drill into the ply fir strips to make a hole for the bolt head to help with the thermal bridge. I then put 1/2" insulation between the fir strips again running perpendicular to the previous layer of insulation.
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This is what the walls look like finished, two inches total insulation. One thing I would do different is use 5/4 board instead of the true 1" (white board in pic) that I used and 5/8" fir strips. The 1/2" Owens Corning pink is just over 1/2" thick so it sticks out past the 1/2" fir strips a little because 1/2" plywood is not REALLY 1/2"; it is more like 7/16". You can get true 5/4 board and use 5/8" ply strips and that should eliminate that issue. Since the insulation sticks out a little from the fir strips I used 1/2" plywood for my finished wall instead of 1/4" ply like I had planned. I was afraid that bulge would make the 1/4" ply wavy so I went with the 1/2"; so far so good.
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On the ceiling I put 1" between the framing members and taped off with the aluminum tape. Then I ran 1/2" perpendicular to that using screws and fender washers to attach it to the roof framing members. Then I used true 1" framing across trailer (lowering my ceiling essentially) and ran another layer of 1/2" again perpendicular to the previous layer. Then between the 1" framing member I added anywhere from 1-1/2 to 2" more insulation. The roof has an arch so total insulation is anywhere from 3 to 4 inches thick the majority being 4 inches thick.
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This is what the finished ceiling insulation looks like.
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My insulation has been completed for about a year and a half so far no issues and it stays nice and comfortable. I also put 2-1/2" in my floor; used screws and fender washers to fasten it to bottom of floor.

Good luck with your build.
Harry
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Re: New here with a question about insulation

Postby ISOTNT » Mon Jan 25, 2021 5:00 pm

This is excellent! Thank you for taking the time to post this. I see you went vertical with the furring strips by using the 1/2" XPS as the thermal break. I didn't even this of this and was searching for something thin to place between horizontal furring strips and the studs. I am for sure going to borrow many of those ideas.

Having owned a large 5er RV (Heartland Big Country) I said never again. I want this to be a camper where if I have a failure on a trip, I never have to set foot in an RV store. I can just hit the hardware store for the fix. To that end, I am planning to use a dual hose portable AC unit as they are not terribly expensive and easily sourced, as well as a simple electric heater, so I want to make sure the insulation is up to the task. :thumbsup:
What did you choose for AC, if any? Thanks!!
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Re: New here with a question about insulation

Postby foxontherun » Mon Jan 25, 2021 7:50 pm

Not a problem; I have had a lot of help and ideas from many on this forum. Glad to help. My AC is a Frigidaire FFRA0611U1 6000 BTU window unit. Mine worked real well in my testing of it. I haven't completed my permanent install yet. In my test, I used my side doorway with it framed in to accommodate the window unit. Here is a link to that thread. viewtopic.php?f=42&t=72833

Flboy completed his second conversion recently and is getting ready to start his 3rd. He has a lot of good info on AC stuff. There are several on the forum that use window units. Here is link to Flboy's latest build. viewtopic.php?f=42&t=65498

There is quite a bit of info on the forum around AC units. I recall that the dual hose AC's don't seem to work as well. I have no experience with them but I do know there are some threads discussing them. Best wishes on deciding what will work best for you.
Harry :)
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Re: New here with a question about insulation

Postby Modstock » Mon Jan 25, 2021 8:16 pm

On your "fighting to remove the side panels" .

There is small reinforcement sheets doubled up behind the walls near the fenders and lower frontal areas.
I had to use a thin pry bar at the bottom to get the walls up and loose.

Also everything goes in a certain order to get other panels off.
Like they start installing wood in the v-nose and work their way back.

Sent from my SM-A115AP using Tapatalk
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Re: New here with a question about insulation

Postby ISOTNT » Tue Jan 26, 2021 1:02 pm

Thanks again, guys.

On the portable AC, I believe the poor performance issues existed with the single hose exhaust units because they would take inside air to cool the condenser and then exhaust that air. So they take in air for both the evaporator and the condenser from the interior and create a negative pressure, pulling in hot air from anywhere the trailer is not sealed. I believe that the dual hose portable solves this as condenser cooling intake and exhaust are purely outside on these. At least, I hope they work better as it is my plan to route both down through the floor. In addition, the one I am looking at also works as just a dehumidifier and so I am hoping to use it as such during the winter time when running the elec heater and just have the condensation drain down through the floor as well.

As for removal of the side panels, the nails that are in the studs aren't too terribly bad as they will spin with the drill as I pull the panels and I can get a center panel off in about 20mins this way, so not too terrible. The trouble is with the panels that meet the corners as these are nailed about every 2" through a square tube stud that is thicker gauge metal than the non-corner studs. These screws wont turn at all as the heads just strip. I have a 3/8 spot weld cutter set coming today though and it has a spring loaded centering pin that I am hoping will work on the screw head of the nails and then I can evenly cut around them to get the panel off and then pull the nails with the vice grips after... What a pain...
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