The low-frequency dielectric properties of cotton fabrics in the fabric thickness direction are examined in relation to the fabric construction, thread count and solid volume fraction (SVF) at five different relative humidity levels. It is found that the real part of the relative permittivity increases with increase in thread count, and this is due to the associated increase in SVF. On the other hand, the imaginary part of the relative permittivity and loss tangent (dielectric loss) show no clear monotonic tendency to the SVF at highly moist environments. Permittivity is observed to change depending on fabric constructions under the controlled SVF. These observations indicate that, in addition to the SVF, the fabric geometrical parameters, which are influenced by construction methods, also need to be considered in low-frequency dielectric analysis.