Outdoor test cells have been extensively used for analyzing the thermo-physical properties of building envelope components under real climate conditions. The paper presents a new test cell facility, under development at the Ecole Spéciale des Travaux Publics, du Bâtiment et de l'Industrie (ESTP Paris) within the framework of a collaboration between the end-use Efficiency Research Group of Politecnico di Milano and ESTP. The facility will allow to obtain reliable estimates of thermal performance indicators of transparent and opaque building elements. A particular care has been taken in the design phase in order to minimize or to accurately evaluate all sources of uncertainty, such as (i) conductive heat losses through the test cell envelope, (ii) time lag of response to transient solar conditions, (iii) levels of airtightness and of resistance to vapour or water penetration.
