Part I of this two-part series reports on an experimental investigation of heat and moisture transfer through clothing assemblies consisting of porous fibrous battings sandwiched by inner and outer layers of a thin covering fabric. The experiments are conducted on a novel sweating, guarded hot plate at -20 °C. The temperature and water content distribution within the porous fibrous battings are obtained for four combinations of two kinds of fibrous battings (polyester and viscose) and two kinds of covering fabrics (one highly permeable nylon and the other a less permeable laminate. Most of the changes in temperature distribution take place within 30 minutes of the tests, and moisture absorption by the hygroscopic viscose fibers affects the temperature distribution. The water content accumulates with time, and water content is higher at the outer regions than at the inner regions of the battings. The accumulation and distribution of water content is a combined result of moisture absorption, condensation, and liquid water movement. The experimental findings form a basis for the development of a theoretical model to be reported in Part II of the series.