Location of vapor barriers in hot humid climates

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Diana Lanser

July 20, 2022 02:21

Hi! I am trying to find some study materials regarding location of vapor barriers and/or vapor retarder in hot humid climates. I live in new england so I am pretty familiar with the conditions here but I am unable to find info in other US regions. Any help will be greatly appreciated.

Thank you,

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  bowermb July 20, 2022 02:58

  As far as the ARE is concerned, vapor barrier should always be located on the warm, wet side of the insulation. For hot, humid climates, that means the exterior side of the insulation. For other North American climates, the opposite is the case. The same concept tracks for the rest of the building envelope (roof/slab).

  Reality is much more complicated, but this is all you'll need to keep straight for the ARE. Any expert subject matter on the topic will be far more in depth than you will need to know regarding air or vapor barriers for the exams.

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  rebekkak August 15, 2022 17:29

  Hi,

  I'm going to ditto Matt's comment.  For the ARE, the vapor barrier goes on the warm side, which generally in the USA in the interior side.  I doubt the ARE would ask you to design a specialized exterior wall for a hot/humid climate.

  You may want to look at a rainscreen exterior wall too.

  Rebekka O'Melia, Registered Architect, NCARB, B. Arch, M. Ed, Step UP,  Step UP ARE 5.0 Courses

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  Diana Lanser August 18, 2022 15:39

  Thank you, I am more interested to know the vapor barrier location in a roof assembly. Here in NE we really do not use vapor barriers in roofs. So, I am assuming for a roof assembly, the vapor barrier should be located in the warmer side of the insulation too?

   

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  bowermb August 18, 2022 16:00 (Edited August 18, 2022 16:05)

  Diane, yes. The rule of thumb is that the location of the vapor barrier relative to interior, exterior, and insulation needs to be consistent around the entire envelope. Think of it like tracing a single, continuous line along the section of your building. The same goes for your thermal barrier.

  Edited to add that the ARE will be very clear regarding the climate region you'll be dealing with. Examples would be Miami, FL for hot-humid and Phoenix, AZ for hot-arid.

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  rebekkak August 21, 2022 20:55 (Edited August 21, 2022 20:56)

  If the attic is not a living space, the vapor barrier would be installed just behind ceiling sheetrock, in the same position as the wall section.
  Hope this helps!
  Rebekka O'Melia, Registered Architect, NCARB, B. Arch, M. Ed, Step UP, www.stepuparchitecture.com

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