Snow Accumulation

[Lynn P]

Hi,
I understand that WUFI considers percipitation occuring below 0°C to be snow. Does it also take into account accumulation of snow on horizontal or sloped surfaces and the insulating effect the snow layer can have?

I am trying to use WUFI to predict if accumulated snow will insulate a roof to the point that the temperature beneath the snow layer will increase above the melting point, creating the potential for an ice layer to form if the snow were to melt, then refreeze.

Any help is appreciated. Thanks in advance.
Lynn

[Thomas]

Hi

Hi Lynn.

I understand that WUFI considers percipitation occuring below 0°C to be snow. Does it also take into account accumulation of snow on horizontal or sloped surfaces and the insulating effect the snow layer can have?

No, it doesn't. For exterior temperatures below freezing, any precipitation is simply ignored (i.e. no water absorption can take place under these conditions). The further fate of snow or unabsorbed rain water is not determined in the simulation. They simply vanish - they do not accumulate into a layer of snow or into a puddle.

I am trying to use WUFI to predict if accumulated snow will insulate a roof to the point that the temperature beneath the snow layer will increase above the melting point, creating the potential for an ice layer to form if the snow were to melt, then refreeze.

WUFI can not predict whether a snow layer will form, or how it will be modified by subsequent melting and snowing. But you can assume that somehow a snow layer with a given thickness has formed, and you can compute its effect on the assembly.

Just include a layer with the desired thickness and appropriate material data (in particular the low thermal conductivity and the low absorptivity for solar radiation). I don't know if the (low) transparency of the snow layer should be taken into account which allows a (small) fraction of the incident solar radiation to reach the top of the roof, which could be treated by means of a heat source.

Then you can simulate the temperatures within and below that snow layer. Of course, any modifications of the layer due to melting and refreezing cannot be taken into account, but you can see how often these conditions occur.

Regards,
Thomas