Transpiration is the evaporative loss of water by plants. It occurs mainly through the stomata in the leaves. Besides the loss of water vapour in transpiration, exchange of oxygen and carbon dioxide in the leaf also occurs through pores called stomata (sing: stoma).

Trees and other vegetation not only block the sun, providing shade, they also cool the air surrounding a home by evaporation. This process, known as transpiration. Large amount of absorbed water are translocated to the leaves and are lost to the surrounding atmosphere. Transpiration has the cooling effect on the plant as well as on the surrounding atmosphere. A roof causes shade, but due to lack of any transpiration like system, it fails to give the same cooling effect as given by a plant.

NCERT Biology Text, Class: XI, UNIT IV: Plant Physiology, Chapter 11 : Transport in Plants, Page no: 187 & The Solar House: Passive Heating and Cooling By Daniel D. Chiras, Page no: 168.