Fire safe installation of metal chimneys through plastic-based insulation materials

There is an increasing attention to sustainable and energy efficient buildings which requires insulation materials with better thermal properties as well as thicker thermal insulation layers over the building envelope. When traditional insulation materials, like mineral wool, are used the insulation layers become very thick. In Finland 400 mm to 600 mm thick layers are now typical. In order to reduce the thicknesses, materials having better thermal properties have been introduced. Using polystyrene (EPS and XPS), polyurethane (PUR) and polyisocyanurate (PIR) based products the thickness of insulation layers can be reduced significantly. During the recent years, numerous building fires in Finland have demonstrated that metal chimneys are a fire risk if their penetrations through the well-insulated roofs are not properly detailed. Similar fires have also reported for example in Italy. Experimental tests are indicating that the thicker insulation solutions and more efficient insulation materials can increase temperatures in the penetration area significantly causing a potential reason for the ignition of flammable materials. Metal chimneys are tested in accordance with standard EN 1856 which requires that the temperatures of roof materials at the safety distance from the chimney do not exceed 85 °C. This requirement is not sufficient for EPS and XPS based products as their metamorphoses occur already at 80 °C temperature. Tampere University of Technology has carried out experimental research to investigate the fire performance a roof construction made of PIR and EPS insulation boards and the actual temperature levels within the chimney penetration area. Also the essential issues regarding he fire safe detailing of the penetration were studied. In this paper the test configuration and the main findings of the research are introduced.