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Homework Statement
The ceiling of a single-family dwelling in a cold climate should have an R-value of 25. To give such insulation, how thick would a layer have to be if it were made of each of the following materials?
(a) polyurethane foam (thermal conductivity k = 0.024 W/m · K)
Homework Equations
R = L/k
L = length(thickness)
k = thermal conductivity
The Attempt at a Solution
Rk = L
25(.024) = .6m
My homework is telling me that I'm wrong and I have no idea why. This seems like a pretty simple and straight forward question. Can anyone help point out where I'm going wrong? Please!