Equivalent R- Value calculation of metal/insulation wall

[jddj]

Hello,

I have a spreadsheet that calculates the equivalent R-value for parallel heat flow through wall studs and insulation. I have always used this spread sheet on typical wall sections with wood studs and batt insulation and seem to have got reasonable numbers. The equation in the spreadsheet is basically U_eq = (1/R_stud)*(stud width/stud spacing) + (1/R_insul.)*(Insul. width/stud spacing) and R_eq = 1/U_eq

I tried using this spreadsheet on a different wall assembly that has thin metal plates between the insulation, so basically I replaced the wood studs information with the metal plate information. I came out with a number that was quite a bit lower than what I had expected. I have seen articles online that state metal stud walls typical have an equivalent R value of 40-50% of the insulation value, and I'm coming up with around 3% from my spreadsheet.

I know I'm not providing any specific numbers, I'm just curious if there is a different approach when dealing with metal as opposed to wood?

Thanks

 

[IRstuff]

There should be no need for a different approach

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[jddj]

Thanks for the response, I will review my inputs and see if anything else looks off.

 

[pmover]

double-check & units of measurement are consistent