A Study of the Effects of Moisture Vapour on the Thermal Transmittance Characteristics of Cellulose Fibre Thermal Insulation

Abstract

The effect of moisture on the thermal performance of cellulose has been investigated both qualitatively and quantitatively. Typical residential wall and ceiling constructions were insulated with cellulose fibre loose-fill insulation at normal densities of application and then subjected to both fixed and cyclic moisture gradient conditions. After 57 days of continuous moisture increase, no catastrophic effects on performance were noted and once cyclic conditions were introduced, the thermal performance improved markedly due to the onset of drying out of the insulation. Quantitative measurements indicate that an approximate 10% increase in moisture content reduces the thermal resistance of a cellulose insulated system by approximately 15%. However, once drying out conditions were established the thermal performance improved once again. Suggestions are made for further work in this and related areas.