This paper presents the initial analytical work performed to quantify the energy benefits of burying ducts under loose fill attic insulation and assess the sensitivity of these benefits to different installation configurations. Results of the analysis are expressed in terms of an insulation wrap R-value that conventional hung ducts would require to achieve an equivalent thermal performance to insulation buried ducts. The performances of larger trunk-type ducts and smaller branch-type ducts installed over or between truss chords in attics with different levels of loose fill fiberglass and cellulose were examined. The various configurations simulated were used to develop general guidelines for predicting the performance of buried ducts. These findings formed the basis for a buried duct credit to be incorporated in the 2005 revision to California’s Title 24.

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