Total R-Value The R-values of any two or three materials can be added to determine the total R-value (R.).
11) Find the total R-value for the walls below.
a) Calculate R, for Wall A.
b) Calculate R for Wall B.
c) Which do you prefer and why?
Wall A
Wall B
Outside: Concrete Block (4") Outside: Brick (4")
Middle: Cellulose in Wall (1") Middle: 1" air space
Inside: Plywood (5/8")
Inside: Plywood (5/8")

Acommercial grade cubical freezer, 4 m on a side, has a composite wall consisting of an exterior sheet of 5.0-mm thick plain carbon steel (kst= 60.5 w/m k), an intermediate layer of 100-mm thick polyurethane insulation (kins 0.02 w/m k), and an inner sheet of 5.0- mm thick aluminium alloy (kal polyurethane insulation and both metallic sheets are each characterized by a thermal contact resistance of r 2.5 x 104 m2 k/w. (a) what is the steady-state cooling load that must be maintained by the refrigerator under conditions for which the outer and inner surface temperatures are 25°c and -5°c, respectively? (b) for power saving purpose, which wall material should be increased/reduced in. thickness in order to reduce 50% of the cooling load found in part (a)? redesign the thickness of the proposed material. 177 w/m-k). adhesive interfaces between the q=575.93 w