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r-values & u-values...

dml955i

Anybody know how to calculate U-value of R-21 insulation?

 
Aug 17, 06 2:53 pm
Josh Emig

1/21

Aug 17, 06 3:10 pm  · 
 · 
dml955i

Yeah, that's what I thought - but still doesn't seem right to me...

Aug 17, 06 3:25 pm  · 
 · 
southpole

Actually I was looking a this the other day-
U is the thermal transmittance, the term used to express heat flow, in particular the steady-state rate at which at which heat flows through architectural skin elements
U = Σ1/R
It is much easier to calculate the assembly of a particular wall than to just take the R value of a particular product.

So any way- R-21- glass fibers 5-1/2”with 6” metal studs @ 16” o.c. = R-9.6
From ASHRAE/IES Standard 90.1-1989

Aug 17, 06 5:15 pm  · 
 · 
southpole

Actually I was looking a this the other day-
U is the thermal transmittance, the term used to express heat flow, in particular the steady-state rate at which at which heat flows through architectural skin elements
U = Σ1/R
It is much easier to calculate the assembly of a particular wall than to just take the R value of a particular product.

So any way- R-21- glass fibers 5-1/2”with 6” metal studs @ 16” o.c. = R-9.6
From ASHRAE/IES Standard 90.1-1989

Aug 17, 06 5:15 pm  · 
 · 

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