Comfort is a key parameter in modern clothing with heat and steam transport through clothing layers the principal physical process in use. This process is likened to fluid filtration in the porous medium. The model of isothermal fluid filtration through textiles is specified and considered as a regular sieve with the effective pore having a cross section area. Further parameters are detailed. This leads on to reliable representation on the effective pore number and their general area per surface unit of textile material. Combinations of effective cubic pores arrangement in some neighbouring plaint-parallel layers of textile material are illustrated. The model is judged suitable for fabrics and nonwovens as any degree of randomness in fibres and pore arrangement in textile material can be accommodated.