just need help with part b A house wall is built with 2x4 wood studs and R11.0 i

Question

just need help with part b

A house wall is built with 2x4 wood studs and R11.0 insulation between the studs. The wood has an R4.9, and 10% of the wall area is wood. Determine the following.

a.) The effective insulation value of the wall. (R)

answer: 9.78

b.) The wood is replaced by 18 ga steel studs. The thermal conductivity of steel is 400 times greater than that of wood, but the percentage of wall area of steel is only 0.30% of the wall. Insulation will fill the remainder of the area not taken up by the steel studs. Determine the effective insulation value of the wall. (R)

Explanation / Answer

b)    effective insulation value of the wall =   L/KA

                                                                = 18 * L/KA

                                                                =   (18 * L) / (400 K * 0.30 * A)

                                                                = (18)/(400 * 0.30) * L/KA

                                                                 =   0.15 * L/KA

                                                                  = 0.15 * 9.78

                                                                   = 1.467

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