Limiting the temperature at the chimney-roof penetration: Innovative roof passage with fins and case to meet the latest European standards and enhance heat recovery

To prevent overheating and consequent fires, European regulations prescribe thermal tests to determine the distance between chimney and combustible materials. Traditional installations are characterized by insulating material at the chimney-roof penetration; however, under critical conditions, including high gas temperatures, thick and insulating roofs, this does not ensure safety. A recent revision of the regulations has been made in light of the increased thermal resistance of building elements. The paper describes an experimental campaign on a marketable device that ensures low temperatures at chimney-roof penetration, limits thermal bridges, and improves heat recovery. Besides the thermal and energy issues, other relevant aspects have been considered, such as marketability, ease of installation, and cost. This device consists of conductive and insulating elements enclosed in a case: the conductive elements reduce the roof temperature by dissipating part of the heat from the chimney and conveying it to both the outdoor and indoor environments. By analyzing the roof temperatures detected in a test where the critical chimney operating conditions have been reproduced, its effectiveness has been experimentally demonstrated. A second test on a similar device without the conductive elements has been also conducted. Finally, results have been compared to those in the literature about tests performed on similar elements. Since results reveal that the external case strongly influences heat transfer, very thick roofs must have chimney-roof penetrations carefully designed to accommodate the latest devices. Designers of timber houses, manufacturers of chimney flues, and standards organizations can benefit from the results presented in this study.