Analysis of causes of the end of service life of a spray polyurethane foam and polyurea roof

¹ Smart City Center of Excellence (Finest Twins), Tallinn University of Technology, Ehitajate tee 5, Tallinn, Estonia
² Department of Civil Engineering and Architecture, Tallinn University of Technology, Ehitajate tee 5, Tallinn, Estonia
³ Department of Mechanical and Industrial Engineering, Tallinn University of Technology, Ehitajate tee 5, Tallinn, Estonia

^* Corresponding author: targo.kalamees@taltech.ee

Abstract

Spray polyurethane foam (SPF) roofs are widely used in North America. Much fewer usage examples and experience can be found in Northern European cold climatic conditions. This study analyses hygrothermal performance and the reasons for the roof’s degradation and end of service life of an SPF and polyurea roof. The service life of the roof is over and major reconstruction is needed eight year after construction. The current study uses field measurements included onsite temperature and humidity measurements and extensive surveying, the roof was opened from several locations and test samples were taken for laboratory tests. The influence of UV radiation on the loss of adhesion was tested. Solar radiation quickly degraded the top surface of the in-situ sprayed polyurethane foam insulation causing a weak connection between the foam layers. Due to mechanically damaged and UV degraded polyurea roofing, water has leaked into the SPF. The water inside or below the foam evaporated during sunny days and broke the adhesion of different foam layers. Larger foam blisters were observed on the upper part of the insulation caused by high water vapour pressure. This is considered the most realistic cause of separation of the SPF layers. The analyse of hygrothermal performance, service life, and durability prediction should be included into the design process, especially for structures with small or without long term performance experience.