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Effective October 1, 2005, you can only
receive credit for “buried ducts” if the work is done in
combination with two additional compliance measures: quality
installation of insulation and duct sealing. When taking the
buried duct credit, a minimum of R-30 insulation must be blown
after the HVAC ducts are installed. Prior to being buried, the
ducts must have at least R-4.2 duct insulation. Only the portions
of duct runs that are directly on or within 3.5 inches of the
ceiling gypsum can take credit for increased effective duct
insulation. Note that ducts resting either directly on the ceiling
gypsum or within 3.5 inches of the ceiling gypsum, resting on
ceiling joists or truss supports, satisfy this requirement and
also meet the support requirements for fl exible ducts in the
California Mechanical Code, Standard 6-5, Section 6.509 (d). As
long as the spacing between support does not exceed the
manufacturer’s recommended intervals, no other support is
required. |
