The effects of air movement on the thermal performance of permeable insulation systems are reviewed. The paper addresses air convection in and around porous insulation exclusively. Air infiltration through the insulation, from uncondi tioned to conditioned space is not covered The results reported indicate that the thermal insulation actually provided by a porous material may differ substantially from that which is calculated by simple application of R-values (as reported in the lit erature), due to air convection effects The application of an airtight membrane can reduce this R-value degradation.
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