>>13611546This,
room temperature usually assumes 293 degrees Kelvin, so you just google the energy density of air (c) which is around 1.006 J / kg*K, the density of air (?) which is 1.276 kg / m^3 both according to engineering toolbox and you specified the volume to be 1 ft^3 and ?T to be room temperature - 0 which is ~293 K = ?T, 1 ft^3 to 1m^3 is 0.0283168466 = V
Now you basically do E = ?Vc?T and get ~ 10.6 J of energy