e.
Yeah, that's mostly correct. If it was out in space it would radiate to th e ~3K background. But here on Earth there is a 300K background. And that could be thought of as a heat load on the box...or another way to think abo ut it is that the 300K is less cold than 0K and so the heat flow from the h ot box is less. Maybe this will help,
George H.