What is the point of green roofs?

[Zarostulus]

I mean, sure they look nice, but they're expensive as hell and it's not like trees create electricity or anything?

[St Rhenium]

Well, firstly, some people also call roofs with solar panels etc green roofs - and they definitely create electricity ;)

In terms of actual greenery though, there is a positive effect on air pollution. Plants use co2 and expel o2, which is great. Green roofs also cool buildings in hot climates, and prevent excess rain run-off in wet climates.

[LucidEnergy]

I wondered this too actually, but I hadn't considered the effect of cooling the building, which would save quite a significant amount of energy, especially in arid climates where power guzzling A/C in commonplace.

At the end of the day, it's better than nothing even if the benefits are small.