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Prefabricated products made of polyisocyanurate (PIR) thermal insulation material covered with cardboard, plastic, aluminium or composite facings are used for thermal insulation of building envelopes. The facing of these products is selected according to their conditions of use, and the effect of the facing on the declared thermal properties of the product depend only on water vapor diffuse properties of the facing. However, at the corners of the building where these products are joined, facings can be in the direction of the heat flux movement and significantly increase heat transfer through the longitudinal thermal bridge formed in the corner of the building. After analysing the solutions for installation of PIR thermal insulation products on the walls and roof corners of buildings, calculations of the heat transfer coefficients of the linear thermal bridges were made, and the influence of various facings and different structural solutions on the heat transfer coefficient value of the thermal bridge was determined. Aluminium foil facing have the greatest influence, but other facings must also be considered. The structural solutions with the greatest increase in the heat transfer due to the effect of the facing were selected, and the influence to the thermal and air tightness properties of the structural solution when facing is removed were analysed, the stability of thermal properties of the thermal insulation material were analysed as well. Proposals for joining PIR thermal insulation products with heat-conductive facings in the corners of buildings were prepared.

An experimental campaign was carried out to assess shear creep behaviour of a rigid low-density closed-cell polyisocyanurate (PIR) foam. Two service temperature values were considered, 20 ºC and 30 ºC, and the applied stresses ranged between 20% and 60% of the corresponding shear strength. The results showed that a stress amplitude of 30% was enough to cause nonlinear creep response. Furthermore, creep deformations were slightly smaller in the tests at 30 ºC, a fact that matched the viscoelastic response of the PIR foam obtained from DMA testing. Finally, creep prediction curves were calibrated through an analytical approach based on the Findley’s power law., This work is part of the research project “EasyFloor – Development of composite sandwich panels for rehabilitation of floor buildings”, involving the company ALTO – Perfis Pultrudidos, Lda., CERis/Instituto Superior Técnico and ISISE/University of Minho, supported by FEDER funds through the Operational Program for Operational Program for Competitiveness and Internationalization (POCI) and the Portuguese National Innovation Agency (ANI) - project no. 3480 (POCI-01-0247-FEDER-003480). The second author acknowledge the grant SFRH/BSAB/150266/2019 provided by FCT, financed by European Social Fund and by national funds through the FCT/MCTES. Acknowledgments are extended to LEST – Laboratório de Estruturas for their material support. The contribution of the Department of Mechanical Engineering of the University of Minho is also gratefully acknowledged in the person of Engineer Pedro Ribeiro. Lastly, the authors would like to thank SIKA Company for suppling the adhesive.