Practical correlations for the thermal resistance of vertical enclosed airspaces for building applications

► The dependence of R-value of enclosed airspace on its aspect ratio was investigated. ► The aspect ratio has a significant effect on the R-value of enclosed airspace. ► Practical correlations are developed for determining the R-values of enclosed airspaces. ► The developed correlations can be easily used by modelers, architects and building designers. ► R-value could be doubled due to installing thin sheet in the middle of enclosed airspace.