In Europe about one third of total annual energy consumption is used in both residential and commercial buildings. In many countries already a building regulation exists to ensure the reduction of energy needs for DHW and space heating. Hence, the interest in reducing summer energy demand has grown in the last few years. The summer behavior of buildings is mostly non-stationary and, therefore, the reliability of simple quasi steady state model predictions can not be taken for granted. Since detailed hourly energy simulations emulate the dynamic interaction between environment, building structure, occupants and indoor conditions, they have the potential to provide relevant information about the building summer behavior and to indicate the possible conservation measures for the reduction of energy consumptions. However, one of the limits for the application of enhanced simulation methods, that sometimes can undermine the reliability of their results, is the difficulty to gather reliable input data. Moreover, if dynamic simulation are used in order to compare different choices, decisions are often suboptimal because of the insufficient knowledge of data that has a large consequence on results. Consequently, in order to broaden the use of building simulation in the design process, it is essentially to clarify some aspects. For instance, one of the biggest objection versus the use of detailed procedure is: "to what extent these methods are meaningful if input data are not reliable?" For this reason, the emphasis of this thesis is on the uncertainties of model predictions. In particular, the research is divided in two parts: the investigation of climate issues and the uncertainty analysis of heat transfer estimation, especially for massive wall. The purpose of the research is to support AE in the choice of the characteristics to which the model predictions are more sensitive. In fact, the results of sensitivity and uncertainty analyzes allow to know the robustness of simulation models and make AE aware if the wrong specifications can lead to uncertain results.

In the perspective of the "Net Zero Energy Buildings" as specified in the EPBP 2010/31/EU, herein a modular unglazed solar thermal facade component for facilitating the installation of active solar thermal facades has been conceived and designed to answer three considerations: (1) easily installable elements, offering high modularity to be sized for the specific needs of the buildings considered, (2) low-price unglazed technology, given by the industrial process already developed for the fridge evaporators, and (3) versatile modules to be used for both new buildings and for existing buildings for energy retrofitting. The existing buildings stock offers a high-potential opportunity to improve the energy efficiency when using such a system. Indeed, the building envelope elements have a significant impact on energy consumptions and performances of the building, and this is a key aspect to consider during renovation. Considering buildings integrating solar thermal (BIST) by the means of facade retrofitting of solar thermal collectors (STC) opens up new challenges for engineers. Facade usage, compared to the traditional roof installations, offers two interesting potentialities: (1) increased available surfaces, and (2) minimization of the unwanted overheating problem, that appears in summer, thanks to the vertical tilt (as the energy production is almost constant over the year). This allows sizing the STC according to the actual heat needs and avoids as much as possible energy fluxes mismatch. The design methodology of such a modular component is the main contribution of the PhD work. The challenges are tackled via a parametric approach. Dynamic simulation tools support the design choices for the energy systems of BIST and to optimize the interactions between the envelope and the STC with the criteria of reducing the overall energy consumption. This methodology is described and applied to the design of a modular prototype of an innovative facade component integrating unglazed STC. We first analyze a variety of typologies of buildings as potential commercial targets of the facade component of unglazed STC integrated facade element. Both residential and non residential buildings are considered. The purpose of this analysis is to match the heat loads for properly sizing the facade elements for each typology. Benchmark models of buildings from the Department of Energy are used such as multifamily houses, hospitals, big and small hotels, schools, offices. These are simulated through EnergyPlus in three European locations (Stockholm, Zurich and Rome) in order to define the yearly heat loads for domestic hot water (DHW) and space heating (SH) needs. Finally, the prototype is conceived and designed as a low-cost product to implement into facades with the criteria of optimizing the energy production. The unglazed STC is combined with a simple configuration of combisystem in order to define some rule of thumbs through Trnsys. By the fact that the energy is produced at lower temperatures, if compared with glazed flat plate collectors, this technology is potential applicable to those buildings having the proper heat loads and the suitable system layout.

In the perspective of “nearly zero energy buildings” as foreseen in the EPBD 2010/31/EU, herein a prototype of a wooden prefabricated BiPV wall is conceived, designed, built and tested. The prototype key concepts, identified according to the recommendations of the IEA Task 41 research project, are: multi-functionality, prefabrication, sustainability and integration. The prototype design is the result of a theoretical study which takes into account both architectural integration aspects and energy performance issues. The latter in particular, is based on the evaluation and improvement of both PV and building-related aspects, through the investigation and implementation of low-cost passive strategies to improve the overall BiPV performance. A modular specimen of the prototype was built thanks to an industrial collaboration and tested through an experimental approach, based on the combination of several phases performed in two test facilities (i.e. INTENT lab and SoLaRE-PV lab) by means of original experimental set-up. The effectiveness of the proposed BiPV prototype configuration is proven by comparing the results of the experiments with monitored data of two BiPV systems (a roof and a façade system) located in South Tyrol (North of Italy). The experimental results are then generalized, providing significant data and experimental expressions for a deeper understanding of BiPV systems energy performance.