Microcapsules including paraffin are currently used for textiles coating in order to deaden thermal shocks. The microparticles comprising a mixture of paraffin and nanoparticles of poly(vinyl) alcohol/hydrated salt crosslinked by methylene diisocyanate entrapped in melamine-formaldehyde resin shell were prepared through in situ polymerization. The influences of nanoparticles on the thermal properties of microcapsules were investigated using scanning thermal microscopy and differential scanning calorimetry (DSC). It was stated that polymer nanoparticles embedded in those microsized capsules allow to decrease the thermal conductivity of the coating and to enhance the protection in the stationary regime. A reasonable volume fraction of polymer nanoparticles reduces the conductivity more than predicted by Maxwell mixing rules. Besides, measurements prove that the polymer nanoparticles do not affect the latent heat and even improve the phase change behaviour as well as the mechanical properties. (C) 2008 Elsevier B.V. All rights reserved.