kylmäkatto

Kylmäkatto, meaning "cold roof" in Finnish, refers to a specific type of roof construction and ventilation strategy designed to keep the roof surface cool. This is primarily achieved by creating an air gap between the insulation layer and the roof covering, allowing for natural airflow.

The principle behind the kylmäkatto is to allow air to circulate freely within the roof space. This circulation helps to remove heat that builds up from solar radiation during the summer months, preventing the roof structure and the living space below from overheating. In winter, the same ventilation can help to carry away moisture, reducing the risk of condensation and ice dams.

Traditional kylmäkatto designs often involve a ventilated attic space. This attic is typically separated from the conditioned living space below by a layer of insulation. Vents are strategically placed at the eaves (soffit vents) and at the ridge or higher points of the roof (ridge vents) to facilitate a consistent flow of air.

Modern interpretations of the kylmäkatto concept can also be applied to unvented or low-slope roof assemblies. In these cases, specialized insulation materials and advanced ventilation techniques might be employed to achieve a similar cooling effect. The ultimate goal remains to manage heat and moisture within the roof assembly for improved building performance and longevity. This approach is particularly common in regions with significant temperature fluctuations and strong solar exposure.