Size of room: (3×5x8)m by 10degree C. Specific heat of air: 1006J/kgC and density of air 1.20 kg/m^3.
I figured out the mass: 144kg and
W:1450kJ
Don’t know how to figure out the time it would take 
How Long Does It Take To Raise The Temperature Of The Air In A Good-sized Living Room…?
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It depends on the power of your heat source. Divide the total heat needed by the heat source power. If you have a 1500 W heater, time = 1.45E6/1500 ~ 1000 s, but remember that the warm air will give up some of its heat to the surroundings (furniture, walls, floor, ceiling, etc), and of course heat may also be flowing out to the outside environment.