Since it seems relevant, what do you think about painting roofs and walls white en masse to reduce the usage of A/C?
> The results indicate that the energy savings ratios of the rooms with the sedum-tray garden roof and with the white roof were 25.0% and 20.5%, respectively, as compared with the black-roofed room, in the summer; by contrast, the energy savings ratios were −9.9% and −2.7%, respectively, in the winter.
It seems that covering the building with a green garden is better than painting the roof white, but the heating costs were higher in the winter for both designs.
I guess that changing the roof could work in climates where the winter is not too cold.
On a side note, I wonder if it would be better to work on better insulation (both roof and sidings) rather than re-roofing a house.
Note: I am not a civil engineer so I have no clue if the paper is good or not.
I suspect that the effect of this is highly location specific, both in terms of climate, as well as average insulation.
But you still often end up with some covering. Not 100%, but I think high enough to meaningfully affect the cost-benefit calculations. Not to mention large commercial buildings with flat roots.
Someone correct me if I’m wrong but I believe it’s the only Canadian city with that requirement.
Above the second floor it had gravel roof I think, I’m not sure what it was but it was very hot in the summer (not so much on the first floor).
After replacing it with elastomer, temperature definitely went down a little bit on the thermostat but I personally don’t feel much of a difference.
This could be because, in the morning, the sun is facing the large windows which warms the inside even more.
Anecdotal, of course. Regardless, roof had to be changed. But the AC is definitely ON when it’s 25C and above regardless of the roof type.
Since 2010, most Quebec building standards have also been updated pretty massively. I don't have references, but where I live, we had 1" insulation in the walls, and now the minimum requirement for new buildings is 1.5". Doors and windows tech have improved a lot too in the past 10-15 years. Overall, as I went through upgrades, our heating bills went down pretty significantly, but AC usage keeps going up.
I've done that to my old workshop, just literally painted the roof white. Dropped ~10 degC during summer, no change in winter.
Seems to me that light roofs would help more during summer when there are lots of sunny days than dark roofs during winter when it's mostly cloudy.
None of this is counting infrared/UV, but reducing visible radiation is still much better than nothing.