Kylmäkattorakenne

Kylmäkattorakenne, meaning "cold roof structure" in Finnish, refers to a building roof design where the attic space is intentionally ventilated and kept unheated. This contrasts with a "warm roof" where insulation is placed directly below the roof covering, and the attic space is part of the heated building envelope. In a cold roof, insulation is typically placed on the attic floor, separating the unheated attic from the conditioned living space below.

The primary purpose of a cold roof design is to manage moisture and prevent condensation. In colder climates, the warm, moist air from the living space can rise and come into contact with the cold underside of the roof structure. Without proper ventilation, this moisture can condense, leading to mold, rot, and structural damage. The ventilation in a cold roof allows this moisture to escape, preventing its accumulation.

Ventilation in a cold roof is usually achieved through a system of air inlets, such as soffit vents, and air outlets, such as ridge vents or gable vents. This continuous airflow helps to remove heat in the summer, reducing the risk of overheating in the attic, and it dries out any moisture that might enter the attic space during winter.

While effective at managing moisture, cold roofs can sometimes lead to ice dams in regions with heavy snowfall and freeze-thaw cycles. The unheated attic can allow snow to linger on the roof surface, and as temperatures fluctuate, meltwater can refreeze at the eaves, forming ice dams. Proper insulation on the attic floor and effective ventilation are crucial for mitigating this issue. The design and construction of a cold roof require careful consideration of local climate conditions and building codes.