How Much Energy is Lost Through Walls When Heating a Home?

[fball558]

energy heating a home?

Homework Statement

During 2 hours one winter afternoon, when the outside temperature was 4° C, a house heated by electricity was kept at 20° C with the expenditure of 42 kwh (kilowatt·hours) of electric energy.

(a) What was the average energy leakage in joules per second (watts) through the walls of the house to the environment (the outside air and ground)?
in watts

(b) The rate at which energy is transferred between two systems due to a temperature difference is often proportional to their temperature difference. Assuming this to hold in this case, if the house temperature had been kept at 24° C (77° F), how many kwh of electricity would have been consumed?
in kwh

Homework Equations

only one i know is
Cm(Tf - Ti) + Cm(Tf - Ti) = 0
where C is specific heat capacity
m is mass
Tf is final temp
Ti is inital temp

The Attempt at a Solution

was going to figure out final temp using above equation and then compare that to the final temp given. but don't know the C so got stuck.

 

[mgb_phys]

Part a, how much energy went into the house, where did that energy go?

 

[fball558]

it is an open system which means the energy is not conserved.
i did conservation of energy but did not think it would be right
because you are loosing energy through the walls which means
you have to input more energy

 

[mgb_phys]

Yes, the energy in all ends up going outside in the long term, so part a is simply asking how many joules were supplied during the 2 hours.