# Energy Efficiency in Buildings and Innovative Materials for Building Construction
## 2 Energy Efficiency in Buildings and Innovative Materials for Building Construction  
In light of the above, this Special Issue was produced to collect the latest research on energy efficiency in buildings by means of innovative and sustainable materials for building construction. There were 23 papers submitted to this Special Issue, and 14 papers were accepted (i.e., a 61% acceptance rate). When looking back to the Special Issue, various topics have been addressed, mainly focusing on energy performance, considering the building envelope and the plant, and on materials' behavior and characterization. In particular, seven papers are more focused on the first topic, concerning the study of the building envelope and plant, while the other eight are more on materials. Papers [1; 2; 3] are focused on simulation techniques for the evaluation of the energy performance of buildings. For example, [PERSON] [1] and her colleagues conducted a parametric study of the influence of the occupant behavior on the energy performance of an office building provided with radiant ceiling panels for heating and cooling. They used TRNSYS, and they concluded that specific human activities influence the annual energy use a small amount and their effects often counteract. [PERSON] and her colleagues [2] made a comparison of two different procedures for energy dynamic model calibration--manual and automatic--using the IDA ICE tool. They built up an automatic calibration procedure and compared it to standard manual calibration for an office building located in Rome, Italy. They found that, although both methods require high expertise from operators and showed good results in terms of accuracy, automatic calibration presents better performance and consistently helps with speeding up the procedure. Lastly, [PERSON] and colleagues developed a dynamic energy model of a single zone building, considering external and internal radiation using Matlab/Simulink. They validated the model with data from the literature and then used the samemodel to evaluate the effect of an added layer of PCM material on the energy consumption. They found a slight reduction of energy consumption for the model with PCM with respect to the one without PCM. Two more papers focused on upgrading the energy performance of historic buildings in Sweden [4] and a stadium in Greece [5]. The paper [4], authored by [PERSON], [PERSON] and [PERSON], evaluates the insulation capability of an hemp lime render compared to a lime render for historic buildings in Sweden. They carried out experimental activity on full scale walls, one renovated with hemp lime and the other one just with lime. They conclude that hemp can improve the insulating characteristics of the lime render, keeping the same appearance of the original external wall, preserving the heritage values, and allowing the building to comply with modern standards, increasing thermal comfort and reducing energy use. In Reference [5], the authors present a roadmap for the energy upgrade of the Pancretan Stadium located in Crete, Greece. Using active and passive solutions, such as the replacement of old openings, the introduction of a PV plant and of an open loop geothermal system, and the installation of energy-efficient lighting and a building energy management system, they could reach an annual energy saving percentage that exceeds 83%. They also improved the RES penetration at 82% versus the annual energy consumption. Papers [6; 7] deal with energy-efficient plants. In particular, [PERSON], [PERSON] and [PERSON] [6] propose an optimal design method to optimize the design of a chiller plant, quantifying uncertainty and reliability. Their method optimizes the chiller capacity and chiller number to minimize the total life cost of the plant. The method is applied to a 50-storey office building in Hong Kong. Their results show that the life-cycle total cost obtained with the novel optimization method is reduced by 26% and 11.4%, respectively, relative to those from uncertainty-based and conventional design methods.