This study presents a simple heat transfer methodology for box double skin fascade. There are a number of numerical methods described in different papers, but at local and European level it is a lack of standards or unique methodologies regarding this system. The methodology presented is an extended and corrected version of a heat transfer method through a double-glazed window described by Oosthuizen and Naylor in [1]. The box double skin fascade consist of an internal double pane window and a 10 mm secure glass as double skin. The methodology incorporates heat transfer by conduction and convection, considering two extreme climatic conditions for exterior temperature. The main purpose of this study is to identify the difference between single-skin fascade and double skin fascade from heat transfer point of view. For this purpose were taken into account and calculated face temperatures, total thermal resistances, transmittances and heat fluxes. Analyze of the heat transfer indicators were described by tabular values and by one year chart for Brqov region, in Romania. For a faster calculation some second degree polynomial equations are proposed, for finding thermal conductivity, thermal diffusivity and kinematic viscosity as a temperature function. For each property it was found one equation for air and one for argon. Argon and air are the most common gases included in window systems. Overall, the study shows an increase in envelope insulation with greatest benefits during the cold season. (C) 2015 Elsevier B.V. All rights reserved.