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From: "ALVIN BACHMAN" <bachman_28@msn.com>
Reply-To: PHYS-L Maillist <phys-l@carnot.physics.buffalo.edu>
To: phys-l@carnot.physics.buffalo.edu
Subject: Re: [Phys-l] Insulation R-value
Date: Fri, 17 Feb 2006 16:57:57 +0000
R is related to the reciprocal of k.
dQ/dt= k A (T1-T0) / L = A (T1-T0) / R
For a set of slabs (same R) , of conductivity Ki and thickness Xi, R = SUM(
1/KiXi )
Units of k are W/(mK) and common units of R are BTU per sq-ft per hour per
F-deg,
which is why everyone drops the units and says R-19 or R-30, etc. )
Al Bachman