SBS Modified Bitumen Roof Membrane

[BESWUFI]

Could anyone help me determine the WUFI Material Properties I should use to user define a generic SBS Modified Bitumen Roof Membrane (ideally) or point me to the best substitute for one that is preexisting in the WUFI Pro database?

Thank you very much for your help!

[Christian Bludau]

Bitumenous roofing felts have sd-values between something like 100 and 300 meters, can be more for alucoated or something like that.
In the generic database there is a "Roof Membrane V13" which is a bituminous felt with sd = 100m.

Christian

[BESWUFI]

To be specific the products I am looking to represent in the model are the Firestone SBS FR Cap (http://technicaldatabase.fsbp.com/downl ... pid=765%5D) and the Firestone SBS Polybase (http://technicaldatabase.fsbp.com/downl ... pid=765%5D).

When I hear the term bituminous felt, I think of a product more like a 30 pound felt (https://www.tamko.com/docs/documents-da ... f?sfvrsn=2).

Is the Roof Membrane V13 bituminous felt able to represent the Firestone products with relatively good accuracy? Or is it more like the #30 felt product?

Thanks!

[Christian Bludau]

For the hygrothermal calculation mainly the sd-value/ permeability and the surface color are from interest. The weight has no real influence because of the thin layer.
Unfortunately your datasheet does not give a permeability value.

So you can use the V13 but you should adapt the water vapor diffusion value / permeability.

Christian