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Community and Q&A

Roof Insulation for Shipping Container Dwelling

jamdzl | Posted in General Questions on

Hey guys, I’m sure I am making this more complicated than it needs to be…

Building a small shipping container cabin (I know, I know).  We are outsulating with eps and polyiso on the walls, about r15 or thereabouts.  On the roof I want to do 4″ of polyiso for r20+, but we get snow so I want to pitch the roof a little (shed roof, no eaves).  So with that in mind I cant figure out if I should keep the 4″ foam as close to the container roof as possible and build a vented or unvented roof above that (venting seems tricky without eaves or ridge and using corrugated roofing), or do I put the foam as close to roofing as possible and have an unvented sealed air space between the container roof and “new” roof?

Thanks much!

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  1. Jon_R | | #1

    Keep the foam tight to the container. Given the air and vapor tightness of a steel container, I wouldn't worry about venting space above it. Unless you are concerned about ice dams.

    1. jamdzl | | #2

      Thanks for the reply! This was my thinking too, my only concern was creating a superheated unvented space above the insulation (hot dry climate zone 3) in the summer and losing efficiency having that trapped air against the insulation?

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