Im doing a project to put a heater in a car to pre heat it. I need to determine how many watts would be needed to defrost a window in a certain amount of time. I know the temp of the outside air and temperature to melt the ice is at least 0 C. I thought i could use it as a semi- infinite solid, but then how is the thickness of the glass taken into account. Also, does the velocity at which the air comes out of the vent matter and how does that fit into the equation. Any help would be appreciated.