I just seen this “article” in 20mins complaining about someone who watered his roof to cool down his apartment. luckily the comments are more balanced than the article.
I for myself see no problem in doing this as long as there is no water shortage. It is proven to be more efficient with badly isolated roofs than an AC.
Was wondering what you opinion is?
Would make far more sense if the person in the article had bought a portable A/C unit, but that is apparently the ultimate environmental evil according to the Swiss who heat their apartments 7 months out of the year.
Also, roof top apartments are uninhabitable in today's heat - I feel for anyone who lives in one. We did in our first apartment here not knowing the reality of it, and I can confirm that an A/C unit works very well even in that situation.
Are you sure about that?
Portable AC units are ridiculously inefficient as both the hot and cold part are within the living space and the exhaust heat is travelling out through an non-insulated pipe
Power for the AC unit is generated to a large extent using water, which is also not 100% efficient and needs to be transported using power lines, etc.
Evaporation water needs a lot of energy, which is absorbed from the immediate environment.
- most of the water will immediately fall down, roof are designed for that
- the thin layer of humidity will evaporate quickly
- the metal cover of the roof might cool down a bit bit not the air inside the apartment
- how long is it gonna last, when there are 15h of continuous sun?
Overall benefits look negligible so I'm inclined to say that it's wasted water.
I think this is the real problem. In Italy I grew up in a last-floor apartment which had a very black tar coating on the top, it was (unintentionally) designed to absorb heat and then hold it. Something should be done on these roofs, e.g. making them double-layer with circulating air inside, painting them white and so on.
Back to the video, if I lived there I would rather bolt two poles to the railing of the terrace and suspend something horizontally to create shadow on the roof and the windows.
I am not pedantic enough to measure everything as you have requested.
I highly doubt that person in the photo waters their apartment roof only one time per day. I also don't see how it would cool it significantly either ...
Do you have any proof as you claim to have that it is better for cooling a dangerously hot apartment?
Tom
I think this is the convincing argument, I'm tempted to measure this with a paving slab out of interest but would anyone bet that a roof doesn't shed 95% plus of the water poured on it? that would mean an aircon would only need to be 5% efficient to be a better solution. If there were aircons that inefficient they wouldn't be allowed on the market, I don't think this argument - wait for it - holds water. Maybe if you were reusing the water an argument could be made.
btw, the outlet tube wasn't an issue, I just wrapped mine in bubble wrap and it radiated far far less heat to the room, sure it's not as efficient as a split unit but it's still going to beat a hosepipe.
Painting the roof white will bring down the temp by a few degrees. Its very common in India, Bangladesh to paint the flat roofs .
In Italy and Slovenia recently, we noticed that rail lines are painted white to reflect heat. In the UK currently, many trains are cancelled due to buckling of the lines.
There are some places rationing water here in CH.
The commune I live in now (Grimisuat, Valais), sent out a communication asking people to not water their lawns as the ~150 hectares of vineyards take precedence. And they also shut off water to all lawns earlier this week up until tomorrow as a way to conserve some water: https://www.grimisuat.ch/commune/cou…tion-6801.html
I’ve been trying to clean the yard, so it’s a bit of a bummer as I sure could use the water, but so be it. I’ll try again on Friday…
I think these things will become a regular occurrence
But yea, total BS.
I ended up booking an airconditioned hotel for the wife and baby to help alleviate some of the heat for them.
Apparently, some houses do now have a “roof mist cooling system” installed:
"If you’d rather enjoy the benefits of a cool roof without the addition of new surface materials or coatings, consider a roof mist cooling system. Also called an evaporative cooling system, a roof misting system lowers surface temperatures by spraying an extremely small amount of water across the roof, allowing the water to cool the roof as it evaporates. Think of it as akin to the way sweating cools your body.
At its most basic, a roof misting system can be little more than a garden hose set to the mist setting and aimed across the roof. (The same method will also quickly and effectively cool your stone patio or wooden deck on a hot day.) More sophisticated roof mist cooling systems typically feature a misting pump with a built-in thermostat, timer and 360-degree misting nozzles that are strategically placed so the water hits every part of the roof. These systems are available for both industrial and residential use."
Source:
10 Ways to Cool Your Roof
https://home.howstuffworks.com/home-…-cool-roof.htm
My colleagues top floor apartment clocked in at 51c this week...