Verification of Density Predicted for Prevention of Settling of Loose-fill Cellulose Insulation in Walls

Abstract

This paper discusses the verification of the density predicted for prevention of settling of loose-fill cellulose insulation in walls when criteria for creep in granular materials are applied. The practical use of an earlier presented theoretical framework and an experimental verification are described. The empirical framework allows a quantitative approach to the problem of achieving non-settling of a loose-fill insulation material in a given wall. The prediction involves the use of three experimentally determined parameters that govern the density of a loose-fill insulation material required to ensure volume stability in a wall exposed to climates. One parameter is determined from tests on a wall exposed to constant humidity conditions and two parameters are determined from tests on walls exposed to time variable humidity conditions. A theoretical description of creep is used that describes the parameter for walls exposed to constant environmental conditions. The parameters for an extended empirical model for predicting creep of material exposed to alternating humidity are determined from the corresponding tests. The uses of the parameters are shown together with associated characteristics for one loose-fill cellulose insulation material under one set of exposures. Full-scale wall tests in one wall cavity configuration under the same set of exposures showed that the method did predict results that are in the right magnitude. In addition it is shown that for many cycles with in-time variable humidity conditions, creep of the loose-fill cellulose insulation material almost reached equilibrium.