Fire safety community is currently concerned about the response of some widely used insulating materials in case of fire, due to the fact that existing regulations do not show how these materials behave in real conditions, which in some applications may be indeed critical. Within this context, several institutions have recently carried out large-scale tests with the aim of testing such insulator’s contribution to fire growth. In this paper we present a set of large scale tests of compartment and façade fires involving materials and configurations of different nature. Our experiments provided evidence that mineral wool insulator preserves its properties in case of fire, whilst other polymeric-type insulators contribute to fire growth in conditions close to the ones present in real fires.