• 4 months ago
Green roofs bring great biodiversity benefits, but have one key drawback as a cooling solution according to a new study.

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00:00All roofs, the principle is that the energy that is coming from the sun is reflected back
00:16straight to the atmosphere and to space, right?
00:19So this energy that is coming in the first place is simply not accumulated in the city,
00:25in the buildings, in the streets, etc.
00:30The heat that is stored in the soil on which the plants are will be released in this form
00:35of sensible heat that you can feel, and they will heat up the air at night, which is what
00:41we found in our study too.
00:43Basically green roofs do decrease air temperature, or are expected to do, but on average throughout
00:49the day, because they heat up also the air at night, you get this kind of null average
00:55decrease in temperature.
01:01This is quite a massive green roof, there is a lot of weight that is added to the building
01:05below it, and behind me you see a roof from another building just across the street, and
01:14this building, for example, could not withhold such a green roof as of now.
01:20So it means that it offers very little options in terms of interventions.
01:26Whitening its roof would actually reflect part of the solar energy again, and reduce
01:30temperature within the building and also in its surroundings probably, but as you can
01:35see behind me, the problem with whitening of roofs, and it's often a cost that has to
01:40be added to it, is the fact that it gets sanded, it gets dirty, and so its reflective
01:45capacity is lowered, and so you have to make sure to maintain it always as white as possible.
01:51I think the more green roofs that we can get, especially in these highly urban areas, the
01:57better.
01:58We do have some orchids here on the roof, some very rare orchids, I believe one of them
02:03is very rare and it's the only one currently known in the UK.
02:09In an environment like this where it is remote, you don't have a lot of footfall, it does
02:13give an opportunity for some of these rare species to thrive.

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