Timber Prefabricated Multifunctional Facade: Approaches and Methods for a Feasibility Analysis, System Design and Testing

A huge amount of the existing building stock is not efficient with regard to energy consumption and this is mainly due to excessive heat losses occurring through building envelopes and to the energy system. Moreover, the ventilation and air conditioning systems are inefficient, influencing the building`s performances and users´ comfort. (4RinEU Consortium, 2016) In Europe, the CO2 emissions generated by buildings could be largely decreased by enhancing the performances of existing building, and the principle “energy efficiency first” is strongly promoted by the new Energy performance of buildings directive. In order to foster the implementation of the renovation, the process has to become faster and the post-intervention performances should be evaluated with a high level of reliability. Therefore, there is the strong need of a retrofit approach able to decrease the energy demand and improve the energy efficiency and building operations, keeping a high level of users’ comfort. In the last few years, a great diffusion of timber technologies has been experienced in the construction field, mainly due to sustainability and environmental concerns linked to the use of wood (Jörg, 2010). The aim of this research is to investigate the performances of a timber-based multifunctional façade system that can be attached externally to the existing building envelope of residential buildings to improve its performances. This intervention is expected to have several advantages, such as the reduction of costs for materials, building time, low disturbance for occupants and, at the same time, this kind of element would ensure a good construction quality from the structural, durability and hygro-thermal performances points of view. These prefabricated modules are often composed by different layers of insulations closed in an envelope structure of timber frame. Modules can be both cladded to the existing load-bearing structure or can be self-supporting. Some prefabricated modules also include membranes for vapour diffusion and airtight layer control. Usually, windows are pre-installed in the module in the production site. More advanced technologies and components can be integrated in the module. In order to investigate all the above-mentioned aspects, different high performing multi-functional façade elements for the complete building renovation has been studied. This thesis aims at supporting with evidence the feasibility and assessing the performances of such prefabricated multifunctional timber-based façade as a new technology for the retrofit of residential buildings by means of computer simulations (both at component and building level) and experiments. This approach has been analysed firstly from the technical point of view at component level. Therefore, different examples of multifunctional timber prefabricated façade will be studied, with a particular attention to hygro-thermal issues of such a layout. These analyses will also be based on testing activities on prototypes. Then, the study has been extended on a larger scale at building level. Thanks to a parametric dynamic simulation, different combinations of technologies will be applied on a multifamily house and results will be analysed from the energy demand and comfort point of view. Finally, this kind of intervention has been studied from the economical point of view. A preliminary life cycle cost analysis has been performed in order to evaluate the comparison between the prefabrication retrofit interventions to more traditional retrofit approach. The numerical models and tests gave promising results for the development of the analysed technology, since no critical spots or damages have been observed within the prototypes and in the modelled geometries. Also the performances evaluation at building scale have been satisfactory, both considering the results and the developed approach for studying the effects of different renovation packages. The preliminary cost analysis proved the feasibility of the intervention as well, although a detailed cost evaluation and LCC analysis turned out to be very difficult to be performed since it would require much more application examples in order to collect real costs and building times.