External sun protection above the windows of a building is the most effective way to keep heat outside of the building. Due to the warmer climate, many people are inclined to purchase energy-consuming air-conditioning systems. By using external sun protection, the heat is kept out and the need for air conditioning is prevented. Internal sun protection is less effective but still useful if outdoor sun protection is not possible. The most effective and natural way of sun protection is using plants (green facades) and trees.