How Revit do the thermal resistance?

[Felipeespv]

Hello to all,

I need to know how Revit do the  Calculation of Thermal Resistance (R) for wall, floor and roofs.

I am making the calculation by hand and Revit show a difference of 4% in Thermal Resistance

So my question is Where can i find the formula or change the formula for this calculation?

Greattings 

[barthbradley]

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Thermal Properties under the Material -- if you have the asset assigned. 

[Felipeespv]

i know that, but the calculation of R.

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