This series of studies investigates the impact of thermophysiologial and sensorial properties and end-use conditions of heat-resistant protective workwear on the wear comfort response. In Part I of this paper, material features and test methods are screened to obtain fabric characteristics that explain wear comfort effectively. Thermophysiological and sensorial properties including liquid moisture transfer properties are assessed for six heat resistant workwear materials with different fiber content, yarn property, weave type, and functional finishes. Based on the thermophysical values, small differences among the test garments are predicted. Measured sensorial properties, obtained from fabric mechanical, surface, and liquid moisture management properties, provide more distinctive comparisons. The remaining moisture (A) is calculated from the evaporated (E) and total driven (T) water to predict the sensation of clamminess after sweating. Results from surface roughness, contact area, and wet cling analysis show that softer yarns, finer fibers and twill weaves produce measurably smoother fabrics with small contact. Also, effects of hydrophilic fiber blending and wicking finishes on the moisture management properties are examined. The former does not affect the liquid moisture management properties while the latter measurably enhances the absorption rate. These results are discussed in relation to the wear comfort response in varying conditions of physical activity and ambient environments in Part II of this paper.