**5. Conclusions**

Except for a 20% vertical (*z*-direction) shrinkage at 800 ◦C, the present study showed that the properties of the analysed thermal insulation did not change much when heat-treated to 1100 ◦C, which is associated with pool fire heat flux levels (250 kW/m2). However, when heat treated to 1200 ◦C, which is associated with jet fire heat flux levels (350 kW/m2), the thermal insulation changed greatly. The density and room temperature thermal conductivity increased from 140 to 1700 kg/m<sup>3</sup> and from 0.041 W/<sup>m</sup>·K to 0.22 W/<sup>m</sup>·K, respectively. The horizontal (*<sup>x</sup>*- and *y*-direction) shrinkage that took place at heat treatment temperatures above 1180 ◦C created gaps in the insulation, i.e., allowed for unrestricted radiant heat flow at exposed locations. However, if a thin layer of thermal insulation that is robust to temperatures above 1200 ◦C is placed at the heat exposed side, the studied thermal insulation may provide significant passive fire protection. It is recommended that this is tested in future studies.

**Author Contributions:** Conceived the project idea, T.L.; guided the study, A.G. and M.M.M.; selected the test materials, performed the mu ffle furnace heat-treatment tests and prepared samples for TGA and DSC analysis and thermal conductivity, A.G.; did all the data preparation, A.G.; did the data analysis, A.G., T.L. and M.M.M.; prepared the artwork and wrote the first draft paper, A.G.; wrote the final paper, A.G., T.L. and M.M.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** The project was supported by Gassco Inc., Norway. A.G. was supported by a Research Council Norway industrial PhD scholarship, gran<sup>t</sup> no. 305336.

**Acknowledgments:** The authors would like to acknowledge Gisle Kleppe for technical support, Leif Inge Larsen for supplying test materials and Emil Hallberg, Rise Fire Research, Sweden, for performing the TGA, DSC and TPS measurements. Technical data for the thermal insulation, which was supplied by Søren Nyborg Rasmussen, Rockwool, is also much appreciated.

**Conflicts of Interest:** None of the participants in the study have any connections to specific equipment or materials being mentioned in the paper.
