The outside walls of a house are constructed of a 4-in. layer of brick, 1/2 in. of celotex, an air space 3^5/8 in. thick, and 1/4 in. of wood paneling. If the outside surface of the brick is at 30°F and the inner surface of the paneling at 75°F, what is the heat flux if
a. The air space is assumed to transfer heat by conduction only?
b. The equivalent conductance of the air space is 1.8 Btu/h ft² °F?
c. The air space is filled with glass wool?

k_brick = 0.38 Btu/h ft °F

k_celotex = 0.028 Btu/h ft °F

k_air = 0.015 Btu/h ft °F

k_wood = 0.12 Btu/h ft °F

k_wool = 0.025 Btu/h ft °F