Hygrothermal and airtightness performance assessment of prefabricated lightweight wall systems for cold climates

Wooden prefabricated wall panels (WPWP) are increasingly used in the residential sector due to their practical and environmental benefits compared to traditional on-site systems. However, there is limited information regarding their influence on the building envelope´s performance, particularly at panel junctions. Therefore, this study investigated the hygrothermal and airtightness performance of two WPWP systems, one standard and one optimized, focusing mainly on panel-to-panel junctions. Laboratory heat and vapor transfer, thermography, and airtightness assessments were conducted over two full-scale prefabricated walls and a reference on-site traditional wall. In addition, hygrothermal simulations were carried out utilizing WUFI Pro, to compare laboratory heat and vapor transfer results with theoretical values. The results showed that the prefabricated walls reduced heat loss through the air leakage sources of the junctions by up to 17.8% and a reduction of air infiltration by up to 76%, compared to the on-site reference. It was also found that using polyurethane foam in panel junctions generated thermal benefits. Still, care should be taken with the amount of polyurethane foam used to avoid increasing relative humidity. In addition, bio-based insulation (hemp fiber) used in the optimized prefabricated wall exhibited adequate hygrothermal performance as it slightly improved the thermal resistance without increasing the risk of interstitial condensation. Overall, the findings demonstrated that wooden prefabricated wall systems can significantly reduce heat loss and air infiltration, highlighting their potential as a hygrothermally efficient alternative to traditional construction methods. • Prefabrication enhances the hygrothermal performance of external walls • Structural joints represent critical points in the envelope • Panel-to-panel junctions with polyurethane foam reduce air leakage at joints • Care should be taken in the amount of polyurethane foam at joints • Hemp fiber insulation can improve wall hygrothermal performance