I was recently mislead by an assembly R value calculator on an insulation company’s website. Surprising because the data wasn’t skewed in their favor, but looks like the flaw was from their failure to take the non-insulation components into consideration. 

Is there an R-value calculator out there for assemblies (looking for roof assemblies in particular) that seems to be pretty accurate and takes the various components (like framing) into consideration? Akos you mentioned one in another thread but didn’t specify. Thanks in advance!