What is the heat flow through the ceiling into the attic in 4.5h?

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SUMMARY

The heat flow through the ceiling into the attic over 4.5 hours is calculated using the heat current equation with thermal resistance. Given a ceiling area of 135 ft², an R-value of 30, a room temperature of 63°F, and an attic temperature of 38°F, the correct calculation yields a heat flow of 112.5 BTU over 4.5 hours. This is derived from the formula H = [A(Th-Tc)] / R, resulting in H = [(135)(25)] / [30] = 112.5 BTU/h. The conversion to joules is also necessary for complete understanding.

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Homework Statement


The ceiling of a room has an area of 135ft^2. The ceiling is insulated to an R value of 30 (in units of ft^2*deg. F*h/Btu). The surface in the room is maintained at 63 deg. F, and the surface in the attic has a temperature of 38 deg. F. What is the heat flow through the ceiling into the attic in 4.5 h?
Express your answer in (a) BTU and (b) joules.


Homework Equations


The equation I used was the heat current equation with thermal resistance.
H = [A(Th-Tc)] / R


The Attempt at a Solution


The equation I used was the heat current equation with thermal resistance.
H = [A(Th-Tc)] / R
= [(135ft^2)(63 deg. F - 38 deg. F)] / [30 ft^2*deg. F*h/BTU]
= [(135)(25)] / [30]
= 3.8 BTH / h

I've already made an attempt to this problems and my results don't seem to not be right. Can someone please help me?
 
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135*25/30 is not 3.8.
 

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