Sunlight cracks windows in newly opened €55m Finnish cultural centre

Two large windows in Pori’s newly built Kulttuuritalo Fiini have split due to intense spring sunlight reflecting off bronze-copper cladding, the facility’s property manager confirmed to Yle on Tuesday.

The cracks appeared in April along the building’s south-facing façade, where the copper’s polished surface created a magnifying effect, focusing heat onto the glass. Property manager Joonas Kekki explained that the sharp temperature contrast—cold spring air against the concentrated solar heat—caused the damage.

“This is a rare phenomenon, at least in Pori, where copper hasn’t been widely used in recent construction,” Kekki said, acknowledging that the interaction between the material and spring sunlight had not been anticipated during planning.

The €55 million cultural centre, funded almost entirely by the private Svenska Kulturfonden i Björneborg foundation, opened in January. While two panes require replacement, Kekki noted that further damage is unlikely as the copper patinas over time, reducing its reflectivity.