Physical properties of nanofiber mats depend on their structural characteristics. So the effects of polymer concentration on the structural characteristics such as fibers diameter, surface porosity and surface roughness of nanofiber mats were measured. To evaluate the surface roughness of nanofiber mats, new non-contact methods such as atomic force microscopy (AFM) and image analysis methods were used. Mean coverage of nanofiber mats was calculated by using theoretical equation. Result showed that increasing the PAN polymer solution enhanced the nanofibers diameter but reduced the surface porosity of nanofiber mats. Because the diameter and surface porosity are parameters that possess mutual effects, a structural parameter was introduced, and then its relation to the air permeability and surface roughness of nanofiber mats was investigated. The results present a strong dependence between structural parameter, and air permeability and the surface porosity of nanofiber mats. It was also found that there is a good correlation between the surface roughness obtained by two methods. Bulk porosity of nanofiber mats is one of the important parameters that affects on their heat and moisture transfer. Bulk nanofiber mats with different porosity were produced by using a modified electrospinning method. The effect of bulk porosity to the air permeability and the coupled heat and moisture transfer of nanofiber mats were investigated by theoretical and experimental methods. A mathematical model was used to describe and predict the coupled heat and moisture transfer of nanofiber mats. The orders of magnitude of terms in the model were determined by using scale analysis method. Although on the basis of the results, order of magnitude of heat transfer by radiation is negligible for nanofiber mats, heat transfer by convection is important. So two models were used to describe and predict the coupled heat and moisture transfer of nanofiber mats. In the first model, it was assumed that heat was only transferred by conduction, and then model was developed by consideration of heat transferred by conduction and convection. The models were solved numerically by finite difference method and theoretical and experimental results were compared to validate the models. Results showed that the bulk nanofiber mats had very high bulk porosity (more than 99%). Experimental results also showed that coupled heat and moisture transfer of these nanofiber mats are high. By results, the presence of nanofiber mats on the substrate tends to considerable reduction in the air permeability but the moisture transfer did not considerably change. Theoretical and experimental results were compared and better agreement was observed between the experimental and developed model results, indicating that the developed model is satisfactory.