Abstract The research presented in this article concerns the modeling of physical processes occurring in protective clothing that determine the ergonomics and thermal balance between its user and the work environment. In the first part, three-dimensional models of real composites based on cotton fabrics and aerogel were designed using the original method of Parylene C deposition in the chemical vapour deposition (CVD) process, which have potential application in thermal protective gloves. The models included geometric parameters of real textiles calculated based on high-resolution X-ray tomography. This technique also allowed for the accurate determination of the porosity of the tested materials and the inclusion of the exact air content in the models without the need to reproduce the complex geometry of fibers in the fabric and microgranules in the aerogel. The results of heat transfer simulations performed using the finite volume method, correlating with the results of the experiment verifying them using thermography, showed that the designed models allow for the prediction of heat transfer with high accuracy despite the use of a lot of simplifications in the geometry. The differences between the modeling results and the experiment range from 0.7 to 5.5% depending on the complexity of the model geometry.