The advancement of smart metering and sensor technologies has opened the door to performing extensive in-situ measurements in buildings and a tendency to carry-out detailed energy and indoor climate monitoring, leading to the availability of the so-called “on-board monitoring data”. The data obtained through these measurements is of high value as it can be used for identification of parameters determining health, thermal comfort, and energy use. In this article, an occupied dwelling has been inspected and monitored for one year and the in-situ measurement and meteorological data are combined to feed a physic-based energy model. For the first time, the detailed data cleaning and filtering techniques are explained to give insight for future similar studies. The data is fed to a 1st – order circuit RC model, equivalent to the building's thermal model. Next, using Genetic Algorithm in a stated optimization problem, Inverse Modelling has been applied to identify four main global thermo-physical characteristics of the building, with a special attention to the heat loss coefficient. The results are compared by analysing three feed data properties: granularity level, period length, and time period, resulting the best fit in the coldest periods. The outcomes have shown the importance of these data properties by revealing differences in the heat loss coefficient in different periods and the weakening of the heat capacitance effect when feeding the model with low granularity level data. The daily values of the heat loss coefficient are then applied in combination with construction data to determine the daily averages of hourly air change rates. Finally, the method has been evaluated in terms of accuracy and precision and the air change rates have been validated using CO₂ concentration and wind velocity. Using this method, it is possible to determine buildings’ main global thermo-physical characteristics as well as the cold periods’ airborne heat losses.

Concerning the high levels of energy consumption in the existing building stock, the necessity for characterization of the building envelop is a well-known issue. Accordingly, numerous methods and practices have been developed and studied to measure the thermal resistance and other thermal characteristics of the walls in-situ. In the current paper, a previously proposed method, the Excitation Pulse Method, EPM, based on the theory of thermal response factors, is further studied and investigated through simulations, to rapidly measure the thermal resistance of existing walls. A prototype is built and introduced to carry out larger number of measurements on site. The triangular pulse's properties such as the relation between its magnitude and its time interval on its corresponding response are investigated. It is shown how changes in time interval can make the method sensitive to the number of residuals and affect its reliability. General constraints and validity domain of the method are studied. In addition, the effect of 3D heat transfer on the performance of the method is further illustrated in light and heavy constructions. It is shown in which cases it is possible to apply the method in-situ and measure the thermal resistance within a couple of hours.

Accurate determination of walls' thermo-physical characteristics is a necessity for execution of energy conservation strategies in existing buildings. In practice, such data is not available because the current determination methods are time expensive and therefore rarely used. Based on the theory of Response Factors, a rapid transient in-situ method, Excitation Pulse Method, EPM, was introduced as proof of concept in a former article. In the present article, detailed conditions for accurate application of the method in heavy and multi-layered walls are further studied. Theory, simulations, and experiments are combined to determine the method's performance in different types of walls, with specific attention to the effects of the walls’ thermal response time and the response factors’ time interval, leading to the accuracy of R_c-value determination. It is demonstrated that the two main thermo-physical properties of a wall, thermal conductivity and volumetric heat capacity, as well as the wall's thickness can be determined using inverse modelling of the Response Factors. The ratios of the response factors have shown to determine wall's minimum thermal response time and to give an indication of the wall's composition. The use of longer time intervals has shown to be advantageous in terms of the accuracy and the performance of the method. Longer experiment times as a result of long time intervals are still considerably shorter than the time required for making measurements according to the current standards and other conventional methods.

Determination of the thermo-physical characteristics of the buildings' components is crucial to illustrate their thermal behavior and therefore their energy consumption. Along the same line, accurate determination of the thermal resistance of the building walls falls into one the most important targets. Following the difference between in-lab, and on site thermal performance of walls, in-situ measurements have been highly recommended. The most well-known practice for in-situ measurement of walls' thermal resistance is the Average Method of ISO 9869, using one heat flux meter and two thermocouples. The method, in comparison with other existing methods is quite straight-forward and therefore, is applied widely in large scale. Despite its simplicity, this method usually needs a relatively long time to reach an acceptable result. The current paper deals with a modification to the ISO 9869 method, making it in many situations much quicker than its original state. Through simulation of walls of different typologies, it is shown in which cases the measurement period becomes longer than expected. It is demonstrated how the addition of a heat flux meter to the aforementioned equipment can lead to a much quicker achievement of the thermal resistance, following the rest of the instructions of the standard method.

Accurate and reliable in-situ characterization of buildings’ thermal envelope is of high significance to determine actual energy use and thermal comfort. In this context, walls’ thermal resistance is one of the most critical properties to be identified. Regardless the numerous studies being carried out to accurately measure the actual thermal resistance of walls on site, the heat flow meter method suggested by the ISO 9869 standard is the one being applied the most. The method requires one heat flux sensor and two thermocouples to measure and estimate the average thermal resistance over a sufficiently long period. Despite the advantages of this method, two problems have been seen in practice: long duration and precision problem. The present article describes and demonstrates how modifications to this standard method can improve the results of the in-situ measurements in terms of duration and precision. Simulations and experiments have been applied to show the effect of using an additional heat flux sensor, opposite to the first one. The modified method aids in obtaining the thermal resistance with a higher precision in a shorter period of time.