Alternating environmental conditions not only influence the long-term performance of construction materials but also the overall energy consumption. Humidity in building partitions has particularly strong effect. Condensation of water vapour and subsequent absorption of water adversely affect thermal properties and, if persistent may lead to the severe deterioration of building envelop. This paper presents the results of a non-contact dynamic study of the condensation process. The investigations give a clear evidence of the strong relationships between the rapid growth of water vapour condensate and the roughness of the surface. Experimental results confirmed that the kinetics of condensation process depends very much on the geometrical characteristics of surfaces-their roughness. It is proposed by the authors to adopt for analysis of the process two parameters-mean arithmetic deviation of profile R-a and mean spacing of profile S-m. Critical value of free Gibbs enthalpy, critical radius of nucleus on surfaces of complex microstructure as well as rate of condensate growth during the second stage of condensation process have been expressed as functions of R-a and S-m. (C) 2006 Elsevier B.V. All rights reserved.