Replacing Plants and Positives of a Green Roof by Mark Benoit

Over the past month, we have been working on improving the green roof walls and making an inventory of plants that are on the roof. First, we replaced any plants on the wall near the instrument tripod. These plants died from the hot summer sun and lack of water. When we placed them on the wall, we packed plant root balls with the coconut fiber, which is a very good water retaining fiber, to help their water retention. This way, they should stay alive longer. The plants on are in pouches as you may be able to see, so there is a little bit of space for extra soil. In order to further help the wall retain water, we packed any empty spaces with the coconut fiber. Additionally, we added a couple more drip lines to the wall to ensure more even and complete watering throughout these pouches. We have yet to see how they hold up in some really hot days, but even after two weeks, they seem to be holding much more water than before. The other green wall that has a black frame around it was also packed with coconut fiber. Soil had fallen out of the containers, so we filled the extra spaces. The coconut fiber is very fine, so we had to wet it before we packed the wall. We were hoping that less soil would fall out of this wall if it retained more moisture as well as providing needed moisture to the plants. After two weeks, it seems to be doing well. If you look closely, you should be able to see the slightly darker coconut fiber on the wall.

From a meteorological perspective, one really interesting idea about green roofs that I have been reading about and learning is a green roof’s impact on water runoff from rain in addition to its impact on the urban heat island. Roofs account for a large portion of an impermeable surface in an urban environment and therefore can contribute to large runoffs. Green roofs can hold some water and ease the impacts of large water runoffs. Since green roofs house plants, these plants transpire and give out water vapor, which can cool a roof through evaporation.  If this large portion of the urban environment is cooler than it originally would be, then the higher temperatures associated with the city may be reduced.

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