Roofs Passive Cooling Performance Through Air Permeability of Tiles: Development of a Standardized Laboratory Assessment Method

Ventilated roofs with clay tiles significantly reduce the incoming thermal heat in summer season, based on “above sheathing” and “under-tile” ventilation concepts (“Ventilated and Permeable Roofs”, VPR). The European LIFE HEROTILE project developed an innovative “Herotile”, designed with an improved aerodynamic shape, optimizing its air permeability while maintaining waterproofness. The project demonstrated the effectiveness of the “Herotiles-based roof” (HBR) in reducing cooling energy compared to other roofing solutions. Although this technological advancement and the well-established benefits of roof ventilation, the potential of VPR/HBR solutions is still poorly recognized at regulation levels, thus limiting their replicability and transferability. One of the actions of the new LIFE SUPERHERO project aims to overcome this barrier by developing a standardized test method to assess the air permeability of tiled roofs and then a recognized classification way for covering products, based on their ventilation performance. A round-robin test has been arranged in three independent laboratories. It consists of blowing or aspirating air down a pipe into a plenum chamber covered by an assembly of tiles. The measured air pressure differences and volume airflow rates are used to determine the air permeability of the assembly. In this work, the developed test method is presented, together with the preliminary results obtained on several tiles typologies available on the market (curved, flat or Herotiles). The outcomes confirm the impact of the tiles shape on the air permeability. Future developments entail the proposal to include the standardized test method in a European Assessment Document or in a CEN standard.