What's your response to this Question? Based on left snip I say (a) but Copilot says (d)

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Sarameri

August 15, 2026 17:43

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  abruno168 August 17, 2026 19:59

  In building construction and assemblies, you're seeing the air barrier in the context of a wall assembly, typically. Consider the language of the question of "generally" the conditions that would require an air barrier. It deals with the exterior, which would eliminate the ceiling, and therefore all of the above, as well.

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  kdegregorio166 August 17, 2026 23:41 (Edited August 17, 2026 23:42)

  You should be able to put your pencil down on the paper and make a continuous line around the building in order to maintain an air barrier. Other wise the air would just leak out wherever the opening was. See red line here:

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  mermann August 18, 2026 10:49

  In sloped roofs, which often include ventilated attics,, on a per square foot basis, more air leaks out through the ceiling than the walls.

  There are often more penetrations (recessed lights, bath fans, attic hatches)….and warm air rises so stack effect pushes air upward.

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  zkoita August 18, 2026 14:58 (Edited August 18, 2026 14:58)

  If its a pick one answer - Walls. 
  If its a pick two answer - Walls and Roof
  
  But Generally, its Walls.

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  kdegregorio166 August 18, 2026 15:40

  It’s not necessarily the roof, it’s at the edge of the insulated space so if your attic is uninsulated it would be at the ceiling.

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  Ralph Hale August 19, 2026 16:14

  Sarameri, 

  
  Because air barriers are often also vapor barriers, you usually want to be careful about having two parallel air barriers in a building section - so you wouldn't typically do both roof and ceiling, for example.  That said, as kdegregorio noted, you really want the air barrier to be continuous all the way around your conditioned space.  The ceiling is the more common place to put your air barrier; if you don't have one in the ceiling, you likely need one in the roof.  Taped gypsum board with sealed penetrations is a very good air barrier that is not also a vapor barrier so long as your interior finishes are vapor-open, and it goes on the interior of your walls and on your ceiling.  
  
  What resource is your left screenshot from?
  
  Best,
  Ralph, the Amber Book Team

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  Sarameri August 21, 2026 23:38

  Ralph Hale Building Construction, principles, materials and systems by Madan Mehta

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  Ralph Hale September 04, 2026 16:07

  Sarameri, 
  
  It's a good resource, but it's not one of NCARB's official references.  I'm not going to say Mehta isn't correct there, because for a relatively large-volume building with a flat membrane roof, it may well be correct because the membrane roof will be an air barrier anyway, but the text is not correct for all building types - mermann describes a condition where the ceiling is by far the leakiest component (at least in summer).  That question isn't very well-written - it misses the nuance of building type and it's not really testing for the actual thing you need to know, which is that air barriers should (generally) be continuous - as kdegregorio shows.  
  
  Best,
  Ralph, the Amber Book Team

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