Suppose you decide to build your new home. You search a department stores websit
ID: 1449806 • Letter: S
Question
Suppose you decide to build your new home. You search a department stores websites for types of materials to cover the walls.You come up with Fiberglass, Rock Wool and Denim batting insulation.The approximate R-values for 1” thickness of these materials are, respectively, 3.1, 4.2 and 3.35.Select below what would your ultimate choice be AND WHY?
3.5” thick layer of Fiberglass
3.5” thick layer of Rock Wool
3.5” thick layer of Denim
2.0” thick layer of Fiberglass + 1.0” thick layer of Rock Wool
1.0” thick layer of Fiberglass + 2.0” thick layer of Rock Wool
2.0” thick layer of Fiberglass + 1.0” thick layer of Denim
1.0” thick layer of Fiberglass + 2.0” thick layer of Denim
2.0” thick layer of Rock Wool + 1.0” thick layer of Denim
1.0” thick layer of Rock Wool + 2.0” thick layer of Denim
Explanation / Answer
Resistance is directly proportional to the length and in the case of a combination, we need to add them because they are in series.
Resistances for all of them:
3.5” thick layer of Fiberglass = 3.5 x 3.1 = 10.85
3.5” thick layer of Rock Wool = 3.5 x 4.2 = 14.7
3.5” thick layer of Denim = 3.5 x 3.35 = 11.725
2.0” thick layer of Fiberglass + 1.0” thick layer of Rock Wool = 2 x 3.1 + 1 x 4.2 = 10.4
1.0” thick layer of Fiberglass + 2.0” thick layer of Rock Wool = 1 x 3.1 + 2 x 4.2 = 11.5
2.0” thick layer of Fiberglass + 1.0” thick layer of Denim = 2 x 3.1 + 1 x 3.35 = 9.55
1.0” thick layer of Fiberglass + 2.0” thick layer of Denim = 1 x 3.1 + 2 x 3.35 = 9.8
2.0” thick layer of Rock Wool + 1.0” thick layer of Denim = 2 x 4.2 + 1 x 3.35 = 11.75
1.0” thick layer of Rock Wool + 2.0” thick layer of Denim = 1 x 4.2 + 2 x 3.35 = 10.9
Maximum resistance thermal resistance is offered by 3.5” thick layer of Rock Wool .
So, that is the best choice.
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