# Thermal and Energy-Efficiency Assessment of Hybrid CLT-glass Facade Elements
## 7 Conclusions  
In this paper, a hybrid structural element composed of Cross-Laminated timber (CLT) and laminated glass was analyzed. The development of the design concept for this element started in 2006, when the first study was carried out within the Croatian project \"Composite structural systems timber-structural glass and timber-steel\" (coordinator prof. [PERSON], with funding from the Ministry of Education and Science) and later within the project \"Seismic resistance of composite timber-structural glass structural systems with the optimal level of energy dissipation\" (2010-2012, Croatia-North Macedonia bilateral agreement, coordinators prof. [PERSON] and prof. [PERSON]). Further developments were then made within the project \"VETROLIGNUM--Multipurpose structural panel\" (Croatian Science Foundation, coordinator prof. [PERSON]). Unlike traditional solutions used for facades (i.e., cellular frame-supported glass panels), this design concept is based on the avoidance of stress concentrations at the CLT and laminated glass joints due to the use of mechanical fasteners or adhesives. The joint was designed as a contact joint over friction surfaces. The hybrid element showed excellent performance under static, dynamic, and earthquake loads and was designed to have good structural performance. The primary purpose of these large panels is to be used as facade elements, but several other characteristics and performance parameters should be addressed and possibly optimized (i.e., energy efficiency, water-tightness, airtightness, optimal thermal characteristics, durability, and required lightening comfort). The focus of this paper, accordingly, was to preliminary evaluate the thermal performance of the hybrid CLT-glass prototype under ordinary operational conditions. The analysis efforts were supported by continuous registrations and thermo graphical acquisitions from a Live-Lab mock-up building that was installed at the University of Zagreb. The expected thermal performance was first analyzed based on the expected behavior of the panel prototype under typical climate configurations in the Croatian region by using the Live-Lab records. The thermal and energy performance indicators for a full-size building were thus assessed via a computationally efficient but professionally-vetted commercial software code (EnCert-HR). A further refined Finite Element numerical model (ABAQUS) was also developed to locally evaluate the typical thermal response of a full-size CLT-glass facade component. The numerical model, as shown, proved promising performance for the hybrid panel in line with European and national requirements. Critical temperature distributions were again observed in the region of the corner joints, which is in agreement with the Live-Lab acquisitions. In subsequent stages of the ongoing study, most investigations will be focused on improving the design details in the contact areas between different building components and materials, as well as investigating new sealing products and various options for adaptive solutions (such as shading systems). Conceptualization, V.R. and C.B. ; data curation, N.P., C.B., and J.B.; formal analysis, N.P. and C.B. ; funding acquisition, V.R. ; investigation, V.R., N.P., and J.B.; methodology, V.R. and C.B. ; project administration, V.R., N.P., and J.B.; resources, V.R. ; software, N.P. and C.B. ; supervision, V.R., C.B., and R.Z. ; validation, V.R., N.P., C.B., J.B., and R.Z. ; visualization, C.B. and R.Z. ; writing--original draft, V.R., N.P., and C.B. All authors have read and agreed to the published version of the manuscript.