Recent development in the construction of houses shows the growing importance of heat loss reduction. For this reason insulation-material is very much on demand. At the moment different insulation materials come into the market and only a small part of their smouldering properties are researched. Smouldering is an essential fire hazard. This thesis includes experiments on 15 insulation materials, compares conventional to ecological-alternative products. The results of the examination show major differences between the products, from no smouldering to progressive smouldering. For this reason, an extension of knowledge on the proper use of construction possibilities with insulation as well as on possible mistakes and risks should be aimed toward designers and builders in the future.