This document describes a laboratory test method to determine the susceptibility of thermal insulation products used for construction against mould growth under specified climatic conditions. The method is applicable to both factory-made products and in situ formed products. Factory-made products include panels, mats, and rolls. In situ formed products are usually those that are delivered loose and installed by blowing-in, poring, or spraying-on, using water and/or binder, whether or not they are also treated using additives. Depending on the insulation manufacturer, the test is carried out with one of the conditions in Table 1. This condition is linked to worst case scenarios selected from real hygrothermal conditions that reflect the end use conditions experienced by insulation products, and to short test duration for mould test. This test method determines the susceptibility of a thermal insulation material to mould growth, but does not determine the suitability for use in a given design (wall, roof, etc.). This method does not predict the resistance of an insulation product to accidental water exposure resulting in saturation of the product (water damage).