Stone-wool insulants in building envelopes are at risk due to their fibrous structure and a thickness of the insulation layer itself. Inbuilt moisture or condensate, that is accumulated during years, begin degradation of binding agents in time. A basic experiment observing changes in material structure when it is exposed to outdoor climate for a period of one year was realized in Nordic conditions. Everyday exterior temperatures, relative humidities, as well as, prevailing weather in Stockholm were registrated and their effect on stone-wool insulants with varying density was analysed. This experiment tries to answer questions what kind of changes stone-wool insulation undergoes.