Device for measuring heat loss through the envelope of a building formed from heat modules (M1, M2,...), themselves provided with inside sensors (65, 70) and with at least one air blower (60,...), located inside the building, with outside sensors (15, 20, 25, 30,...) located outside the building, with a member for the exploitation of data and also with a characteristic building file characterised in that said device comprises members for measuring for at least one of the three following heat coefficient indicators: - heat transfer coefficient by transmission Htr(W/K) defined in standard NF EN ISO 13790:2013, with this coefficient being an intrinsic property of the envelope of the building tested, - heat transfer coefficient by air renewal, due to infiltrations of air, Hve(W/K) defined in standard NF EN ISO 13790:2013, with this coefficient depending, on the one hand, on the air-tightness of the envelope and, on the other hand, on the climate conditions and in particular the wind, - global heat loss coefficient through the envelope of said building, due to infiltrations of air and to heat transmissions, Htot(W/K) defined by the following formula: H tot = H tr + H ve with Htot depending, on the one hand, on the intrinsic properties of the envelope, i.e. heat transmissions and air-tightness and, on the other hand, on the climate conditions and in particular the wind, and in that said device further comprises: - within the member for the exploitation of data, a set of calculations for determining the uncertainty on said heat indicators, taking account of all the sources or error listed: -- uncertainties of measurements, i.e. random and systematic errors, -- uncertainties of the conventional data used in the calculation of modelling uncertainties, and in that the measuring is based on a plurality of heat models (GBA, GBB, GBC,...) associated with a member for selecting the best model, with regards to the measurements taken. - heat transfer coefficient by transmission Htr(W/K) defined in standard NF EN ISO 13790:2013, with this coefficient being an intrinsic property of the envelope of the building tested, - heat transfer coefficient by air renewal, due to infiltrations of air, Hve(W/K) defined in standard NF EN ISO 13790:2013, with this coefficient depending, on the one hand, on the air-tightness of the envelope and, on the other hand, on the climate conditions and in particular the wind, - global heat loss coefficient through the envelope of said building, due to infiltrations of air and to heat transmissions, Htot(W/K) defined by the following formula: H tot = H tr + H ve with Htot depending, on the one hand, on the intrinsic properties of the envelope, i.e. heat transmissions and air-tightness and, on the other hand, on the climate conditions and in particular the wind, - within the member for the exploitation of data, a set of calculations for determining the uncertainty on said heat indicators, taking account of all the sources or error listed: -- uncertainties of measurements, i.e. random and systematic errors, -- uncertainties of the conventional data used in the calculation of modelling uncertainties, and in that the measuring is based on a plurality of heat models (GBA, GBB, GBC,...) associated with a member for selecting the best model, with regards to the measurements taken. -- uncertainties of measurements, i.e. random and systematic errors, -- uncertainties of the conventional data used in the calculation of modelling uncertainties,