The Wall of a House Consists of a Slab of Concrete

question 20

Multiple Choice

The wall of a house consists of a slab of concrete (of R-value 0.5) with an insulating board (or R-value 1.5) firmly attached to the inside. The concrete and board are in thermal contact with each other. The temperature inside the house is 20 $\degree$ C and outside the house is 0 $\degree$ C. Determine the rate at which heat is lost through one square metre of wall (in W) .

• A)20
• B)10
• C)13.3
• D)40
• E)2.0