9.0 VAPOR RETARDERS
9.1 New Construction
9.1.1 Many building scientists question prescriptive use
of vapor retarders, however some building codes continue
to require a vapor retarder on the warm side of
insulated walls. Most cellulose manufacturers recommend
against use of vapor retarders in walls insulated
with spray-applied cellulose. CIMA is not aware of any
endemic problems resulting from this practice.
9.1.2 A vapor retarder is not required under attic
insulation when the attic is adequately ventilated. A
vapor retarder must be used when the cold side of a
ceiling cannot be ventilated (See Section 10.0 for Ventilation)
9.1.3 A ground surface vapor retarder such as plastic
film is recommended when there is a crawl space
beneath the floor. (See Section 10.0 for Ventilation)
9.2 Existing Construction
9.2.1 Most cellulose producers regard vapor retarders
as unnecessary with dense-pack cellulose under most
conditions. If design temperatures are below -15 degrees
F. (-26 degrees C.), the interior surfaces of exterior walls
and ceilings where the cold side cannot be ventilated can
be painted with a vapor barrier forming paint.
9.2.2 A ground surface vapor retarder, such as plastic
film, is recommended when there is a crawl space
beneath the floor. (See Section 10.0 for Ventilation)
http://www.cellulose.org/userdocs/TechnicalSpecifications/CIMA-TechnicalBulletin02.pdf
