In this problem you will estimate the heat lost by typical house, assuming that the temperature inside is Tl 20*C and the temperature outside Tout 0"C. The walls and uppermost ceiling of a typical house are supported by 2 6-inch wooden beams (kood 0.12 W / (mK)) with fiberglass insulation (kins 0.04 W/(mK)) in between: The true depth of the beams actually 5.625 inches, but we will take the thickness of the walls and coiling to be Lwall = 18 cm to allow for the interior and exterior covering: Assume that the house cube of length L 9.0 m on side_ Assume that the roof has very high conductivity, SO that the air in Ine attic is at the same temperature as the outside air: Ignore heat loss through the ground The effeciive thermal conductivity of the wall (or ceiling) kcft is the area-weighted average of tne thermal conductivities of the wooden beams and the fiberglass insulation that make uUp each ol them: Allowing for the fact that the 2 6 beams are actually only 1.625 inches wide and are spaced 16 inches center center; calculation of this conductivity for the walls yields kff 0.048 W / (mK) For simplicity; assume that the ceiling also has the same value ot kaff

Part A How much heat per second H (= Q/AT) is lost trom the house due heat conduction? Glve your answer In watts, rounding to thc nearest 10 W

Part B Let us assume that the winte consists ol 150 days in which Ihe oulside temperature 0"C. This will give the typical number of "heating degree days Observed in winter along the northeastern US seaboard_ (The cumulative number of heating degree days given daily by the National Weather Service and used by oil companies determine when tney should fill the lanks of Ineir customers_ Given that gallon (3_ of oil liberates Qg 14 10" when burned, how much oil will be needed supply the heat lost by conduction from this house over winter? Assume that the heating system 759 efficient