How to Insulate a Shipping Container Roof Using Foam Sheet

 

How to Insulate a Shipping Container Using Foam Sheet

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This post shows how I started to insulate a shipping container using foam sheet.

I am working on my 40 foot shipping container so that I have a nice condensation free insulated room that I can both heat and cool. the first thing I did was frame in a wall about 10 feet from the back of the box.

Next I got out my diy hot wire cutter and made a rigged up fence so I could cut 4×8 sheets of 3/4 inch foam to 3.5 inches so they could fit in the roof corrugation.

Next I used construction adhesive to glue the foil side of the foam to the metal roof. I did this because some glue will melt the foam, also because I wanted the vapor barrier on the metal side.

My dad and I rigged strips of plywood to hold the ends of the foam as the glue set. It was a two man job, but one person can do it if they are organized.

After I ran out of glue, we built a t-post to hold a piece of plywood in the center of the foam strips so they should set without sagging.

Later I will show the video of the framing, as well as show how we finish the roof. for now, I am out of money for materials and glue and spray foam are expensive.

This might not be the right way to insulate a shipping container.  However, it is how I went about doing it. If you have a comment or a better way please share.

I still have 30 feet of this one, and 40 feet of my dad’s to insulate.

Spray Foam Would Have Been Easier

How to Insulate a Shipping Container Using Foam Sheet

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I still think spray foam is the best way to insulate a shipping container.  However, it costs a great deal to do it right.

I don’t even want to spend the money to even attempt a DIY solution.

This is why I like the foam as I can buy a sheet or two every check.  It may cost the same in the end, but it feels cheaper.

Using closed cell sheets is a decent alternative, and much better than any other ideas I can find online.

First we measured and saw that the depth of the corrugated channels in my roof were 3/4 inch deep (where not bent).

I bought some 4×8 sheets of 3/4 inch closed cell foam with a aluminum vapor barrier on one side.

In part one of how to insulate a shipping container, we cut and glued in the strips to level out the roof corrugations.

 

How We Insulated the Roof

 

The original slats were glued in using construction adhesive.  However, some fell because of the condensation and flexing.  Consequently, I did not want to rely on glue alone.

Side Wall For Support

What I did was build a wall along the back of the box that was 3/4 plus the width of a 2×4 (roughly 3.5 inches) from the top of the roof. This would allow a 2×4 joist and a sheet of foam to rest tightly against the wall.

I then cut joists that would span from the top of the wall in the back of the box to the divider wall we framed in earlier. I had to notch that 2×4 so it could sit against the stud wall and allow for the 3×4 inch sheet. (the video will show this)

Once the joists were cut we balanced them up on the walls. I put the two nearest the box sides close to where they were to rest.

Next, I spread the middle joints apart because the foam would have to bend toward the middle so I could wedge it up and around (Again, the end of the video will show this).

Once the joists were close to being in place, I spray foamed the gaps around my foam slats.  I also put construction adhesive on the large sheets of foam (first cut to size).  Neat we starting from the back and wedged them in place.

Once the first foam sheet was in place We rotated the 2×4 to lock the sheet up against the roof of the container.

The next sheet went in and was made to but up against the first and a temporary support was used to hold the two sheets up tightly against the roof without the support of any of the joists.

After the third and last sheet was placed, the 4 joists were nailed in place.

Now the foam sheets are held by glue, expanding spray foam, and 4 2×4 joist edged into place.

Next We Need to Insulate Side Walls

Now I have to frame the side walls.  Next I need to figure out how I am going to insulate the shipping container walls.  I am having problems because the sides are not as square as the roof.

I am not done, but you can get an idea about how I Insulate a Shipping Container.

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