Energy testing of buildings

Thermal transmittance U-value (or global K factor) is defined (ISO7345) as the thermal flow crossing a unit area in presence of a temperature difference (1°K) between indoor and outdoor environments (in stable conditions). The thermal transmit-tance is the global amount of heat moving from indoor to outdoor through a surface (wall). This value expresses the wall insulation capacity and can be used to define the energetic efficiency of buildings. The value is also required by the Euro-pean directive 2002/91/CE concerning the energy performance of buildings.

LSI Lastem designes and supplies a compact and easy to use system for the measurement of the as-built thermal tran-smittances (U-values) in compliance with ISO 9869-1:2014 “Thermal insulation — Building elements — In-situ measure-ment of thermal resistance and thermal transmittance — Part 1: Heat flow meter method”. Each measurement spot inclu-des one data logger, two outside face temperature sensors, one inside face temperature sensor and one inside face heat flow sensor. Measurements are collected on the data logger memory and downloaded on PC where, using InfoFLUX pro-gram, thermal conductance can be obtained using two methods: “average method” (ISO9869:1994 standards) and “black box method”.

A temperature difference of at least 10°C between the two faces of the wall is needed throughout the measurement. When this difference remains stable during the time it is possible to obtain a stable thermal flow between the wall. In good condi-tions the thermal transmittance result can be reached in 5-10 days of measurements. If data downloading is carry out du-ring the meaasurements, using the InfoFLUX program it is possible to understand when the result is completed because the chart shows when conductance value is near to the horizontal asymptote, in this situation the thermal transmittance can be fixed.

Energy testing of buildings


  • Compact and easy to use system;
  • Kit including data logger, sensors and PC program for U-Value calculation;
  • Measurement and storage of three contact temperatures and one heat flow values;
  • PC program for U-factor calculation in compliance with ISO9869:1994;
  • Data logger memory permits several months of measurements;
  • The data logger can be connected to a wide range of indoor thermo-hygrometric sensors.
documents LSI Lastem

Energy testing of buildings


IEQ and environmental comfort

Suitable Products


Data Loggers

Range of data loggers for enviornmental applications for fix/portable, outdoor/indoor uses. Wide number and type of inputs. Low power consumption

Sensori per misure in ambienti indoor

Indoor environment sensors

Range of sensors to measure physical and chemicals quantities in the thermal environments, environmental quality and air quality applications in confined spaces



Range of PC programs for the data management, data display, data reporting, data communication and special applicative solutions for environmental calculation

Valeria Menichini

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