Water-cooling of the roof

Air conditioning, fans, and anything related to keeping it cool, such as insulation. This would include any posts generally discussing how to keep it cool, such as which types of blocks are better insulators.... ideal wall thickness for keeping an A/C house cool, etc.

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Water-cooling of the roof

Postby schuimpge » Sat Mar 16, 2013 10:33 am

Hello all, I am renovating an old town-house. It has the standard tiled roof at the front and fiber/concrete plates at the back.

Passive cooling as much as possible, so I have several ideas I want to put in.
- PU foam under the tiles and in the overhang so roof is 100% closed.
- large glass 'chimney' with ball fan on top to pull air up and out from under the roof (vents in every ceiling)

Active cooling with water:
Seen a factory cooled like that. Idea is to have a sprinkler keeping the roof wet.
Sprinkler would be a long PVC pipe with small holes drilled in it at the highest point of the roof.
Collection through gravity with a rain-gutter and pipe to the holding tank.
Water is then pumped up to the sprinkler again.

My idea is:
- solar panel to drive a 12v pump. Total cost approx. 10,000 baht including PVC fittings
- auto top-off for evaporation. (from your normal tank, simple float switch) 500 baht
- no batteries, clouds or night time don't require the pump to work as it is cooler.
If the water would get hot, it's easy to install some 12 volt fans with cooling ribs in the tank to transfer heat out.

The water is cheap, so evaporation might be an issue but for cost it doesn't matter.

Your roof stays clean instead of having all dirt collecting until the next rain-shower and then splashing over your terrace.

Hope to get some reactions to test this idea.
Thanks and regards,
Luc
The 2 combined systems should make for a very cool attic.
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Re: Water-cooling of the roof

Postby schuimpge » Sat Mar 16, 2013 11:04 am

Did some more searching on it.
Quite a lot of info on the web.
Did not find anything with solar power though.

Cheers,
Luc
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Re: Water-cooling of the roof

Postby Roger Ramjet » Sat Mar 16, 2013 11:30 am

schulmpge,
Luc, here's how I think it will work:
The pu foam under the tiles will, along with the rotating exhaust fan will keep the house cool except for walls and windows, which you haven't addressed. Anything more you do to the roof will be a waste of time because the pu foam and rotating exhaust fan will have cooled that already. Using water to cool what has already been cooled is a waste. Your problem will be with the walls and windows and the heat transfer there.
I too have a townhouse and have done what you are suggesting, I also used insulation bats over the ceiling to keep the cool air in the rooms. My biggest problem is the walls that are made of red brick and the windows, some of which are louvred (I haven't done the whole townhouse yet) and that is where the major problem is now.
In other words your problem is no longer with the roof, but the rest of the house.
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Re: Water-cooling of the roof

Postby schuimpge » Sat Mar 16, 2013 11:51 am

Good point RR. Will need to test some before and after the PU goes on.
I know they advertise with an average 5-10' Celcius for the foam. No idea how much the fan-tower will add to that.
Windows will all be replaced, still checking on prices and types, double or not, alu, uPVC...etc.

Walls are all plastered red brick with a light yellow gloss paint, reflects a good deal.
But walls sure are single brick.

The temperature difference is huge with cement plaster though. Replaced a window with brickwall, not yet plastered and painted on the outside. Daytime, you can cook an egg on it. Too hot to touch while the surrounding old and finished wall is not hot at all, just ambient temperature.

Some more checking to do. Maybe the panels will then solely be used to drive a water pump from groundfloor tank to a roof tank water system with gravity feed into the house.

To be continued...
Luc
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Re: Water-cooling of the roof

Postby Sometimewoodworker » Wed Mar 27, 2013 7:11 am

schuimpge wrote:My idea is:
- solar panel to drive a 12v pump. Total cost approx. 10,000 baht including PVC fittings
- auto top-off for evaporation. (from your normal tank, simple float switch) 500 baht
- no batteries, clouds or night time don't require the pump to work as it is cooler.
If the water would get hot, it's easy to install some 12 volt fans with cooling ribs in the tank to transfer heat out.

Luc
The 2 combined systems should make for a very cool attic.


As far as the water cooling it would work well. I've seen it in Kanchanabury and it was good. However there is no point in cooling the water. The energy of evaporation is so much greater that going from 20 deg or 40 deg makes almost no difference in the cooling effect.

However if you use PU foam there is no point in doing the water bit.

We are currently building a water house that will have water cooling and a rain effect roof.
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Re: Water-cooling of the roof

Postby Vince_c » Fri May 10, 2013 2:11 am

I have tried to cool baked tiles using water from a hose, sprayed on the roof (high volume).
Whereas it might have reduced temperature in real terms, the increase in humidity made it 'feel' much worse, both inside and outside (in the near vicinity) the house.
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Re: Water-cooling of the roof

Postby Shastadad » Fri May 10, 2013 8:05 am

If you want to see a water-cooling of the roof gone horribly wrong go to Pattaya International Hospital on Soi 4 between 2nd and Beach Road in Pattaya

Evidently some architect sold them on a system of plastic panels with water flowing over them on the roof of the patient waiting area. It is so bright that they had to purchase many beach type umbrellas that are spaced throughout the waiting area to provide indoor shade :oops: I hate to think of how much their electric bill must have gone up to cool the lobby


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Re: Water-cooling of the roof

Postby oil » Fri Apr 18, 2014 1:24 am

schuimpge wrote:Active cooling with water:
Seen a factory cooled like that. Idea is to have a sprinkler keeping the roof wet.
Sprinkler would be a long PVC pipe with small holes drilled in it at the highest point of the roof.
Collection through gravity with a rain-gutter and pipe to the holding tank.
Water is then pumped up to the sprinkler again.

My idea is:
- solar panel to drive a 12v pump. Total cost approx. 10,000 baht including PVC fittings
- auto top-off for evaporation. (from your normal tank, simple float switch) 500 baht
- no batteries, clouds or night time don't require the pump to work as it is cooler.
If the water would get hot, it's easy to install some 12 volt fans with cooling ribs in the tank to transfer heat out.

The water is cheap, so evaporation might be an issue but for cost it doesn't matter..



i tried something like that on our garden house, the effects there arent that hight cause its just a wooden shag without rooms,
however i am total fan of it by now and will implement something like that on the main house. The key to success imho, is not to keep the roof wet, just to give it water with a sprayer for like 10 seconds every 5 minutes.
The massive cooling happens from the evaporation not from a wet roof.

best example is when we get out of the shower its freshy / cold just for a few minutes, as long we are under the shower and the water is running there is no evaporation effect and hence no cooling.

if you have some updates on your current status with it keep this thread updates i am curious about it
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Re: Water-cooling of the roof

Postby schuimpge » Fri Apr 18, 2014 7:34 am

Sorry, I cancelled the idea and went with RR's assessment. Painted the roof white and have PU foam under it.
Paint helped a lot with cooling.
Cheers,
Luc
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Re: Water-cooling of the roof

Postby vanda » Fri Apr 18, 2014 9:11 am

oil wrote:
schuimpge wrote:Active cooling with water:
Seen a factory cooled like that. Idea is to have a sprinkler keeping the roof wet.
Sprinkler would be a long PVC pipe with small holes drilled in it at the highest point of the roof.
Collection through gravity with a rain-gutter and pipe to the holding tank.
Water is then pumped up to the sprinkler again.

My idea is:
- solar panel to drive a 12v pump. Total cost approx. 10,000 baht including PVC fittings
- auto top-off for evaporation. (from your normal tank, simple float switch) 500 baht
- no batteries, clouds or night time don't require the pump to work as it is cooler.
If the water would get hot, it's easy to install some 12 volt fans with cooling ribs in the tank to transfer heat out.

The water is cheap, so evaporation might be an issue but for cost it doesn't matter..



i tried something like that on our garden house, the effects there arent that hight cause its just a wooden shag without rooms,
however i am total fan of it by now and will implement something like that on the main house. The key to success imho, is not to keep the roof wet, just to give it water with a sprayer for like 10 seconds every 5 minutes.
The massive cooling happens from the evaporation not from a wet roof.

best example is when we get out of the shower its freshy / cold just for a few minutes, as long we are under the shower and the water is running there is no evaporation effect and hence no cooling.

if you have some updates on your current status with it keep this thread updates i am curious about it



There was a system I helped set up similar to this, however it wasn't for a roof, as this type of system works better out of direct sunlight, it was for a sitting area that could be kept cool in the hotter months through evaporative cooling. It is more or less based on the design of a Coolgardie Safe. http://en.wikipedia.org/wiki/Coolgardie_safe
-Simple retic. system
-Solar powered pump
-Float valve to maintain water level, I think we used one from an old toilet...
-Water retaining material
-Catchment at the bottom of the material to recycle unused water

You may find using some type of cloth on your roof will help hold water in place for evaporation, proving more surface area to evaporate, instead of it sliding down the incline of your roof before is has a chance to be more effective.
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Re: Water-cooling of the roof

Postby Roger Ramjet » Fri Apr 18, 2014 9:42 am

If you are going to use water on the roof then why not plant something it?
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Re: Water-cooling of the roof

Postby oil » Fri Apr 18, 2014 11:43 am

Roger Ramjet wrote:If you are going to use water on the roof then why not plant something it?

as for insulation goes that is definatly the best, a bit like a hobbit house, however with a so called green roof, tons of other side issues arrive
- you need a very strong and solid construction which can carry the weight of at least 50+ cm soil layers
- you need a good water drainage system there as well, that none of the water hits on your roof
- your main roof need to be absolutley water tight, and you need to make sure that none of the plants you put there can penetrate the moisture barrier

i was going for that idea inititally but i doubt i can get all the materials in TH to make this idiot proof water tight and still can hold the heat and foremost the enourmous weight of a green roof
the other downturn of a green roof is with a soil layer of only 50 cm you are forced to give it water most of the time otherwise the plants will dry out quickly

although i liked the hobbit style house a lot, i skipped that idea for now
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Re: Water-cooling of the roof

Postby fredlk » Fri Apr 18, 2014 12:32 pm

oil wrote:
Roger Ramjet wrote:If you are going to use water on the roof then why not plant something it?

as for insulation goes that is definatly the best

PU-Foam is better.
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Re: Water-cooling of the roof

Postby Roger Ramjet » Fri Apr 18, 2014 1:53 pm

fredlk wrote:oil wrote:
Roger Ramjet wrote:
If you are going to use water on the roof then why not plant something it?

as for insulation goes that is definatly the best

PU-Foam is better.

Exactly my point. The only viable way to get the most out of the water you use (waste) in cooling a roof is to go "hobbit" style.
Otherwise it's PE or PU foam.
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Re: Water-cooling of the roof

Postby schuimpge » Fri Apr 18, 2014 3:43 pm

PU Foam and white paint on top of the roof. Preferably glossy. Sunshine literally bounces off of it.
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