If the floor of the attic is poorly insulated and there are no breathing vents, the space will heat up enough to melt the lower layer of snow repeating the avalanche. The other method for ice dam formation is poor attic insulation and venting. On asphalt roofs, the snow doesn’t shed but rather it accumulates at the bottom of the roof and refreezes when the temperatures drop overnight. This can lead to avalanche problems seen on metal roofs where the snow slides off the roof in big sheets. On metal roofs and even asphalt roofs to some extent, radiant heat will cause the snow to melt on the bottom and drip to the gutter. The newly melted water now refreezes as temperatures drop overnight. As the snow melts, it drips down to the gutter still clogged with ice.

The first method is temperature fluctuations which cause snow to heat up during the day and then freeze overnight. The snow melting process can be initiated through various methods. Ice dams are melted snow refrozen by the winter air to keep it simple. This dam will cause numerous areas of damage if left untreated. The melting snow is unable to shed off the roof before refreezing forming a dam. Ice damming starts at the edge of the roof and even in the valleys where the snow trapped on the roof begins to melt.