Product Brochure
8
Cold Climate
Vapor retarders are required and should be placed at the interior.
– Building envelopes with moisture storage claddings like concrete or brick
– Building envelopes with low permeability exterior sheathings such as extruded polystyrene
Mixed-Humid Climates
– If heating-dominated, locate vapor retarder at the interior
– If cooling-dominated, locate vapor retarder at the exterior of the building envelope
or, ideally, install a smart vapor retarder, as it is able to adapt to the varying moisture
conditions
Mixed-Dry Climate
be low, but defer to your local building code for what is required
Hot-Humid Climate
Climate Inuences Vapor Retarder Selection and Placement
In certain climate zones, vapor retarders are mandatory building code requirements, but some may not realize that
there are, in fact, sub-categories or Vapor Retarders often called Variable or Smart, as they are able to to adapt to
environmental conditions.
home increases. Large portions of North America are considered “mixed-climate,” where the moisture-drive direction
is balanced between the winter and summer seasons. In these regions, homes using traditional polyethylene vapor
retarders may successfully keep moisture out of the cavity in the cold season, but traps it there during summer when
the moisture drive reverses. The increased use of moisture-retaining cladding, such as masonry, fiber cement and
stucco, which release moisture into the building cavity, can exacerbate this issue.
Four Classes of Permeance
Vapor Barrier
(Class I)
Vapor Retarder (Class II)
Semi-permeable
(Class III)
Permeable
(Class IV)
0.01 0.1 1 10 100
Plain Gypsum Board (45 - 85)