In this research, internal thermal superinsulation in residential buildings is experimentally and statistically evaluated in terms of potential thermal bridging effects. As a consequence of significant deviations in thermal resistance values in buildings at post-retrofit, large amounts of heat losses occur through non insulated building elements such as separating walls. Therefore, it is of vital importance to determine the level of energy loss due to such thermal bridges through an internal thermal superinsulation retrofit conducted in a typical UK building. 20 mm thick fibre-silica opaque aerogel blanket is implemented internally on the walls of a test bedroom, and the heat flux from the separating wall is measured and compared for the cases of pre and post-retrofit. The results reveal that the average amount of heat loss through the non-insulated separating wall at the post-retrofit is 5.86 W/m(2), whereas it is only 0.66 W/m(2) at the pre-retrofit. The results are also verified through a statistical model, which is presented for the first time in literature. The novel model is capable of providing information about potential energy loss from non-insulated walls as a function of location. (C) 2016 Elsevier B.V. All rights reserved.