I'm interested in building a steel Quonset hut home in central Texas. I've done a fair amount of research on what's involved, but I'm stuck on insulation.

The IECC defines minimum insulation requirements for light-frame construction like wood & steel studs, but it's less clear (to me, at least) how those requirements translate to a unique structure like a Quonset hut, where the steel sheathing is the structure.

See the code here (mainly TABLE R402.1.2; I'm in Climate Zone 2):


With regard to minimum insulation requirements, how does the International Energy Conservation Code (IECC) apply to steel arch buildings like Quonset huts?


  • What constitutes a "wall" and a "ceiling" in a semicylindrical building? End walls are obviously walls, but is the entire remaining arched structure then a ceiling?
  • Which exact R-values am I targeting in which exact portions of the building?
  • Does anything from R402.2.6 Steel frame ceilings, walls and floors. apply here? A Quonset hut is steel but isn't exactly "framed," so I'm unsure.

A popular Quonset hut insulation approach seems to be 2" of closed-cell spray foam, which totals ~R13, which makes me curious if then the steel arch structure is considered a large "wall." Probably not a safe assumption, though, as these are often used for garages, which can often be uninsulated (i.e., don't have the same minimum R-value requirements as a home), and therefore this may just be done for comfort, not to satisfy any code.

  • 1
    Since you are in central Texas you might want to give the people at the Monolithic Dome Institute a call and see if they can help. They make dome structures that are somewhat similar to what you're talking about and might have some input on requirements of non-standard buildings. – JPhi1618 Mar 13 '19 at 17:58

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