1. Introduction

It is well known that buildings and constructions use a lot of energy, buildings take approximately 40% of the energy consumption in the EU and 36% of the CO2 emissions. Therefore, as a part of the broader goals of energy efficiency and reduction of CO2 emissions, the EU has introduced the energy performance of buildings directive (European Commission , 2020). The energy transmitted through the building maintenance structure will have a great impact on the cooling or heating demand of the building. For example, in (Andrew Stone et al., 2014) states that there are several most influential parameters like U-value of the building envelope, heating system efficiency and the building geometry takes 75% of the energy rating variance. It has become a common way to calculate U-value through ISO standard and estimate building energy consumption based on the results. However, according to (Rasooli & Itard, 2016) mentioned that the some building with poorer energy label the energy consumption is overestimated to 50%. In another research shows that after the investigation for 77 new buildings in Sweden, the design value has on average 20% lower than the real energy demand (Danielski & Fröling, 2015). Not only for the new building, the U-value for old building envelope after long period time of use has also different U-value than the design value. Some study from Energy Saving Trust (EST) Solid Wall Insulation Field Trials and studies by Glasgow Caledonian University (GCU) for Historic Scotland and the Society for the Protection of Ancient Buildings (SPAB) found that the researched wall measured U-value have always around 1.3-1.4 W/m2K when the design value is 2.1 W/m2K (Rasooli & Itard, 2016; Rasooli & Itard, 2016). If the U value of the building envelope can be measured correctly, then the performance of the building can be better estimated and improved, which can save a lot of cost. The current well-known method to determine U-value is the heat flow meter method, it can show a reliable result but also needs a long period to finish the test. Especially when the surrounding environment of the temperature sensor is unstable, the experiment time is at least 1 week. However, the usual practice is to extend the experiment time to two weeks or even longer (Li et al, 2014). This undoubtedly adds complexity to the long-term experiment. Another way that has become more widely used in the recent is to use infrared thermography technology, this technique can consider all possible heat transfer phenomena when measuring the surface properties of various research investigations, (Fokaides & Kalogirou, 2011). In this experiment, the team will also test the emerging dynamic method. Contrary to the desire of static heat flow meter to eliminate the influence of thermal mass, the dynamic experimental method hopes to characterize the influence of thermal mass, it can provide a deeper understanding of building performance and can be applied to a wider range of conditions (Biddulph et al., 2014). In this report, the three mentioned methods will be used and compared with each other based on theoretical values, and some values from other studies will also be used as references.

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