On the use of internal thermal insulation systems for the retrofit of buildings' exterior walls

In this paper, a quantitative analysis of internal thermal insulation systems (ITIS) is made based on three basic requirements: thermal bridges minimisation; control of temperature variations within the exterior wall; and the need for at least a minimum thermal mass. This study relies on computer simulation using different tools depending on the purpose of the calculation. The selected software applications were in compliance with the available European standards, namely for thermal bridges and dynamic parameters. The effect of different outdoor climate conditions was evaluated, taking also into account the typical indoor hygrothermal characteristics of Portuguese residential buildings such as common temperatures and ventilation rates. The results of this study quantitavely show that, for the analysed requirements, the ITIS option should not be disregarded, provided that some proper measures are guaranteed. It can be an interesting solution for retrofitting exterior walls as long as thermal bridges are corrected whenever needed; that temperature variation within the exterior wall (which depends greatly on the colour of its outer surface and on the location of thermal insulation, and less on its thickness) are compat-ible with its resistance (with or without reinforcement measures); and that the availability of a minimum thermal mass is assured.