In the lofty heights of mountainous regions, zinc roofs have become a common sight. As you ascend, zinc becomes the material of choice for roofing ski resort hotels, mountaintop restaurants, and cable car stations. The Helbronner cable car station, standing proudly at 3500 meters above sea level in the Alps, is a shining example of zinc's resilience in high-altitude environments. Moreover, in regions with harsh winters like the Nordic countries, zinc is a prevalent roofing material due to its ability to withstand extreme cold.
Behaviour of Zinc in Cold Climates
Zinc's impermeability makes it impervious to the freeze-thaw cycles that can damage other roofing materials. Once installed, zinc remains unfazed by low temperatures and enjoys a long life. Even when snow accumulates on zinc roofs, the surface finish remains largely unaffected. However, after particularly snowy winters, a temporary white discoloration may appear as the snow melts and reveals any retained meltwater. This discolouration gradually fades back to the normal color of zinc, although this effect is absent in finishes like elZinc Rainbow® or elZinc Advance®.
Design Considerations in Cold Climates
Two key design considerations for zinc roofing in cold climates are ice dams and snow retention. Ice dams are localized build-ups of ice caused by refreezing meltwater, which can lead to water ingress and other issues.
Underlying Phenomena - Behaviour of Snow Thaw on a Zinc Roof
Snow thaw on a metal roof can occur due to three phenomena:
Air Thaw: Snow melts from the top down due to above-freezing air temperatures, with meltwater filtering through the snow layer.
Sun Thaw: Unreflected sunlight heats the zinc trays, causing snow to melt from the bottom up. This can lead to sudden shedding of the snow blanket or ice dam formation.
Heat Loss Thaw: Heat escaping from the building melts snow from the bottom up, with meltwater draining towards the eaves.
Recommendations to Minimize Ice Dam Formation
Proper insulation and ventilation can limit heat loss thaw. Venting the roof creates an air space between the insulation and decking, protecting against heat loss thaw. Roof design should ensure all slopes receive some sunlight, while dark colors can help induce sun thaw.
Design and Installation Considerations for Cold Winters
Snow and ice retention measures, such as snow guards, are essential in snowy regions to prevent dangerous snow slides. Standing seam roofing systems using aluminum pipes can be used for snow retention without perforating the zinc.
Best Practice for Storage and Transportation of elZinc® Products
When storing and transporting zinc, it should be kept in a well-ventilated, dry space with gradual temperature changes to prevent condensation. After transportation, unpacking should be done immediately in a dry environment, avoiding direct exposure to cold air to prevent condensation formation. Proper packaging during transport is crucial to avoid damage and condensation buildup.
In conclusion, zinc roofing is a durable and reliable choice for cold climates, offering resilience against freeze-thaw cycles and providing effective protection against the challenges of winter weather.