Leafy Roof

Can a roof garden bring down the indoor room temperature of the building?

The result of a roof garden differs in the way you plant your garden. 

The soil has a higher thermal mass compared to timber and metal, which would store the heat from direct sunlight and release it to the building interior possibly in the night time. 

In the daytime, you get a lower room temperature underneath a roof of soil compared to a roof in metal or timber. 

The leaf of the garden plant has the ability to turn radiant energy (heat) from the sun into food and oxygen through photosynthesis. 

This is the reason you can feel room temperature coolness under the shade of a tree canopy than under the direct sunlight except when the surrounding wind is warm. 

When you have big leafy plants that can block the direct sunlight, not only that you will get a lower temperature in the daytime, the soil does not get direct sunlight and thus, it does not store heat and release it in the night time. 

You get a relatively low temperature during the daytime and the nighttime.