# Fire Tests of Load-Bearing, Light-Steel-Framed Wall Systems Insulated with Polyurethane Foam
## 5 Conclusions  
This paper presents the details of three fire tests conducted on a newly proposed composition for LSF wall systems using PUR foam in the cavities, with spacers separating the GFBs from the steel structure. Two specimens were identically sheathed with two A1 GFBs, while the third specimen were sheathed with two A2 GBFs and one outer A1 GFB. Based on the experimental results and discussion, the following conclusions can be drawn:  
1. During testing, the integrity and insulating properties of the tested LSF panels were undisputed, and all test specimens showed indications of structural collapse. Nevertheless, a reliable mode of failure (governing the FRR criteria) cannot be specified because the insulation used is combustible and the tests were terminated before the failure criteria were reached.
2. Two 12.5 mm thick layers of A1 GBFs delayed the temperature rise in the steel bars by about 50 min (observed at lower positions of thermocouples) to 60 min (observed at higher position of thermocouples), while the configuration with two A2 GBFs and an outer A1 GFB caused an additional delay of 30 min.
3. Post-fire test observations showed that all three test specimens exhibited similar local buckling of the steel members in the lower segment near the rigid nodes.
4. The results obtained on two identical specimens under the same conditions demonstrate the need to perform a larger number of nominally identical tests, especially to broaden the basis for verification when fire behaviour modelling is used.  
Since there are no data in the existing literature on the behaviour of LSF walls with combustible cavity insulation materials, the results presented in this study are valuable for future studies. Although combustible PUR insulation was used, the study showed promising results for the application of developed LSF panels in prefabricated and modular structures in both residential and commercial buildings where an FRR of more than 60 min is required. To comprehend the behaviour of LSF panels with PUR insulation in a fire situation, particularly with regard to their potential application in specific building types, it is crucial to investigate the potential release of toxic gases from the used PUR foam on the side exposed to the fire. Cost-optimal configuration of the wallboards should be established by further research, which could lead to testing of different types of wallboards with their different position in the cross section of the system, even introducing the possibility of an installation layer, which could enable reduction in penetrations through the system, easier airtightness barrier installation and easier detailing (regarding the fire resistance) of multiple panel connections--especially if the installation layer is filled with mineral wool or similar non-combustible insulation material.  
Conceptualization, M.J.R., D.S. and T.S.; methodology, M.J.R., D.S. and T.S.; formal analysis, M.J.R., D.S., B.M. and T.S.; investigation, M.J.R., D.S., B.M. and T.S.; writing--original draft preparation, D.S. and T.S.; writing--review and editing, M.J.R., D.S. and B.M.; visualization, M.J.R., D.S. and B.M.; project administration, M.J.R.; funding acquisition, M.J.R. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the European Union through the European Regional Development Fund's Competitiveness and Cohesion Operational Program, grant number KK.01.1.1.07.0060, project \"Composite lightweight panel with integrated load-bearing structure (KLIK-PANEL)\".  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
**Conflicts of Interest:** The authors declare no conflict of interest.