Retrofit of an entire building is often a multitask procedure that requires significant resources in order to minimize its’ energy consumption. Therefore in several cases, shell retrofit is more appealing and approachable. This article presents a technique that was developed and validated in the field, during the RESSEEPE project (FP7). The technique allows the estimation of the U value change of a retrofitted shell element and directly link’s this change to the factual retrofit impact. The method is based on remote, real time, infrared scanning of just one surface temperature of the element before and after the retrofit. Apart from the element’s surface temperatures, both the indoor as well as the outdoor temperature are also required. The method is very easily and remotely set up, is completely non-intrusive, while its’ cost efficient leasing model makes it quite promising. Thereupon the purpose of this study is to present a reliable, objective and cost effective assessment of a shell element retrofit impact by measuring the U value changes. As this estimation could affect the decision making process, regarding the verifiability and accuracy of the earnings claims, one can only realize this work’s contribution, as it provides facts where opinions are formed.

Keywords : Shell retrofit; U value change; monitoring modul.