Far-off objects don't just appear smaller as they recede, they also become less distinct, with little visible detail, paler colors, and reduced contrast of tone. This is known as atmospheric, or color perspective, and is the primary means of creating the illusion of space in a rendering. Tiny specks of dust in the atmosphere cause colors and tones to become paler in the distance, where objects have exceedingly little distinguishable detail. The colors also become "cooler", with more blues, grays, and blue-greens.
As far as I know, and for the most part, there isn't a render engine that can produce this natural phenomenon. So, take some artistic liberties in post production, to bring your exterior renderings to a whole new level, by using levels and curves, to achieve the color perspective effect.