## 1 Introduction  
Energy efficiency in buildings is one of the key priorities to face the challenges derived from climate change in Europe due to the fact that buildings account for 40% of energy consumption and 36% of CO2 emissions [1]. In this context, it is clear that building renovation efforts are required to increase the energy performance of buildings through the so-called Renovation Wave [2], whose main objective is to double the annual energy renovation rate of the European building stock by 2030, whereas only 0.2% of the buildings are currently being deeply renovated each year [1]. Europe has already established an ambitious plan to reduce 55% of the greenhouse emissions by 2030 [3], as well as to increase the current 3% of the overall building stock that is compliant with the energy performance regulations nowadays in force [4]. In order to reduce the primary energy use and carbon footprint of existing and new buildings, three main strategies can be addressed: (i) reducing their energy demand resource to improved passive behavior, (ii) supplying the required energy in the most sustainable manner, from production and distribution up to end users, thanks to local energy harvesting and efficient energy systems, and (iii) increasing the use of clean, renewable energy sources [5]. In this line, the passive exploitation of the thermal inertia in building structures as Thermal Energy Storage (TES) systems, as well as their active management through direct coupling with active energy production technologies (giving rise to the concept of Thermally Activated Building Systems, TABS) [6; 7] have demonstrated their high potential for energy savings, since they enable the reduction of peak loads while improving indoor thermal comfort conditions [8]. The application of these technologies supports more sustainable constructions and offers new possibilities to comply with the Climate Action Plan [3; 4] objectives by 2030. Nevertheless, there is an increasing worldwide trend towards lightweight constructions, which are characterized by low thermal capacity values. To overcome those drawbacks derived from this specific characteristic, incorporating innovative functionalized materials, such as phase change materials (PCMs) into building applications is a promising strategy. This would increase the building's thermal inertia, dampening down the peak indoor temperatures thanks to the passive thermal regulation provided by the additional (latent) energy storage capacity of the incorporated material [9]. In this context, this work aims at demonstrating and verifying the increased performance (both in terms of indoor temperature regulation as well as of energy use reduction) of two innovative mortars with the incorporation of microencapsulated PCMs, which are suitable for application into indoor finishing solutions. Two commercial PCMs were used within the analyzed mortars: CrodaTherm(tm) ME29P [10] and Micronal(r) DS 5001X [11]. Their characteristics are described in Section 3. Although the application of PCMs to constructive solutions is attracting more and more interest nowadays, the specific development of PCM-based mortars has not been widely explored, and most of the related literature still focuses on the lab-scale characterization of materials without addressing real-scale applications [12; 13; 14; 15; 16; 17]. Those mortars hereby proposed have been developed, fully characterized, and demonstrated at real scale in the context of the European SUDOKET project [18] together with a set of other Key Enabling Technologies (KETs) for innovative eco-friendly built environments. They were developed targeting the reduction of overheating while promoting indoor passive thermal regulation and energy efficiency in lightweight constructions under warm southern European climate conditions. Their experimental characterization in terms of microstructural, mechanical, and thermal properties was first addressed and was presented in a previous research paper by [PERSON] et al. [19].