Based on the following chart, what material has the least overall embodied energy? Material Energy (megajoules per kilogram of building material) kg of CO2 per kg (kilograms of carbon dioxide per kilogram of building material)
aluminum 155 8.24
bricks 3.00 0.24
concrete 1.11 0.159
lumber 8.5 0.46
steel 20.1 1.37

lumber

concrete

steel

aluminum

bricks

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