Passively Cooled House

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Re: Passively Cooled House

Postby gliffaes » Tue Sep 18, 2012 12:52 pm

Roger Ramjet wrote:Before we all venture into this argument too far I think it would be advisable to read this: http://www.yourhome.gov.au/technical/fs46.h
Because, the topic is passively cooled house it might pay to stick to that subject.


Not Found?

Link here

http://www.yourhome.gov.au/technical/fs46.html
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Re: Passively Cooled House

Postby gliffaes » Tue Sep 18, 2012 1:02 pm

The windcatcher's effectiveness had led to its routine use as a refrigerating device in Persian architecture. Many traditional water reservoirs (ab anbars) are built with windcatchers that are capable of storing water at near freezing temperatures during summer months.
http://en.wikipedia.org/wiki/WindcatcherThis will show you how using passive cooling, with water evaporation can reduce temperatures significantly below ambient.

While some of the architecture does store, it also is able to cool by passing hot air over water using evaporative cooling thus cooling buildings below ambient.

All of this however true is worthless speculation without information from the OP in his design[/quote]
And in a dry climate not humid like Thailand?
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Re: Passively Cooled House

Postby Sometimewoodworker » Wed Sep 19, 2012 9:22 am

gliffaes wrote:And in a dry climate not humid like Thailand?

Water cooling works even in humid climates. Not as well to be sure but as long as the humidity is less than 100% it will work.

To give you an example that you can see in many places in Thailand. The mist water sprays on fans. These provide cooler air than the fan by itself. To be sure this is not a passive cooling example but it does show that even in a medium to quite high humid climate evaporative cooling is effective.

Also AAMOF the humidity in NE Thailand, unless it is raining, is usually in the 50~60% range so giving ample chance for evaporative cooling to work
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Re: Passively Cooled House

Postby fredlk » Wed Sep 19, 2012 9:34 am

Sometimewoodworker wrote:Also AAMOF the humidity .......

AAMOF?? A relation of your wife's? I don't understand abbreviations at all apart from KKK, SS but then some might call me old-fashioned.
Sometimewoodworker wrote:the humidity in NE Thailand, unless it is raining, is usually in the 50~60% range

Here at the coast in the hills the humidity is similar and seldom reaches the 70% mark. It's been grey and raining now for a few days and it's been around the 80 to 90 % mark a lot of the time.
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Re: Passively Cooled House

Postby Sometimewoodworker » Wed Sep 19, 2012 9:41 am

fredlk wrote:AAMOF?? A relation of your wife's?

It could be

(Fred Translation) :lol: "As A Matter Of Fact"

FWIW.

(Fred Translation) :lol: "For What It's Worth"
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Re: Passively Cooled House

Postby gliffaes » Wed Sep 19, 2012 2:04 pm

Sometimewoodworker wrote:
gliffaes wrote:And in a dry climate not humid like Thailand?

Water cooling works even in humid climates. Not as well to be sure but as long as the humidity is less than 100% it will work.

To give you an example that you can see in many places in Thailand. The mist water sprays on fans. These provide cooler air than the fan by itself. To be sure this is not a passive cooling example but it does show that even in a medium to quite high humid climate evaporative cooling is effective.

Also AAMOF the humidity in NE Thailand, unless it is raining, is usually in the 50~60% range so giving ample chance for evaporative cooling to work


But surely this then becomes mechanical cooling not passive as you have to pump the water to mist it using electric?
Dont get me wrong Im not saying it wont work to some degree but I dont see it as passive cooling.
Far better for me to surround house with trees, make sure slab is not in contact with sun and on the ground, build house on a hill not on stilts, orient house away from sun, use light weight building materials or double walls insulated all of which will use no mechanical method for cooling.
The only way to move the water for cooling would be electrical unless you got a solar/wind power pump etc and how long before the body of water heats up as temp variants arent that great here?
When the wind stops blowing there will be no effect with some of the suggested options.
Im fortunate to have stuck the maids house about 12 foot in the air due to the shape of the land, now I have to surround it with trees which will slow the wind down and Ill lose some of the effect its a bit of a compromise as is normal.
The method the Arabs use would probably work better for their dry hot climate.
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Re: Passively Cooled House

Postby Sometimewoodworker » Wed Sep 19, 2012 2:11 pm

gliffaes wrote:
Sometimewoodworker wrote:
gliffaes wrote:And in a dry climate not humid like Thailand?

Water cooling works even in humid climates. Not as well to be sure but as long as the humidity is less than 100% it will work.

To give you an example that you can see in many places in Thailand. The mist water sprays on fans. These provide cooler air than the fan by itself. To be sure this is not a passive cooling example but it does show that even in a medium to quite high humid climate evaporative cooling is effective.

Also AAMOF the humidity in NE Thailand, unless it is raining, is usually in the 50~60% range so giving ample chance for evaporative cooling to work


But surely this then becomes mechanical cooling not passive as you have to pump the water to mist it using electric?
Dont get me wrong Im not saying it wont work to some degree but I dont see it as passive cooling.

That is exactly what I said :?: and you have quoted me saying that "To be sure this is not a passive cooling example"


Far better for me to surround house with trees, make sure slab is not in contact with sun and on the ground, build house on a hill not on stilts, orient house away from sun, use light weight building materials or double walls insulated all of which will use no mechanical method for cooling.


All of those are good too.

The only way to move the water for cooling would be electrical unless you got a solar/wind power pump etc and how long before the body of water heats up as temp variants arent that great here?


With the passive cooling you don't rely on the water to absorb the heat. You use evaporative cooling. And the idea is to build in a way that directs the air flow over your body of water, this cools the air (evaporative cooling) and to a small extent the water (in the Persian case the water is probably cooled down to 4 deg C) but we want cool air not cool water. You then direct this cooler air through the areas you want cooler.
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Re: Passively Cooled House

Postby Sometimewoodworker » Wed Sep 19, 2012 2:38 pm

gliffaes wrote:and how long before the body of water heats up as temp variants arent that great here?


I think that there is a degree of misunderstanding here.

The water involved is not used as a heat sink. It is the energy involved in the change of state from liquid to gas that provides the cooling. This change uses a significant amount of energy which is why it is cooler near any body of water.

The trick is to channel the flow of air over the greatest area of water you can then direct that air into the places you want it.

Passive evaporative cooling would use things like the wind towers.
Active evaporative cooling use things like the mist spray, trickling water over a roof, artificial waterfalls etc.


FWIW (Fred translation :lol: For What It's Worth) there is research that shows that the difference between using cold (>5 deg C) and warm (<25 deg C) water makes almost no difference to the evaporative cooling effect. This is due to the great amount of energy required in the change of state from liquid to gas, compared to the energy neded to raise the temperature of the water by 20 deg C

http://heatisland2009.lbl.gov/docs/221000-narumi-doc.pdf is a very interesting study in Osaka City. the humidity in summer is very high. they got "whole-day average falling by 16.4°C" and a reduction in air conditioner energy use of 36%.
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Re: Passively Cooled House

Postby gliffaes » Wed Sep 19, 2012 2:54 pm

For this to work surely water temp has to be lower than air temp otherwise there will be no lowering of ambient temperature.
In this example off RR's site the water is in shade but even so that will still be probably 30c here? and as the day progresses will rise losing the effect.
Keeping the water permanently in shade will also be tricky
I cant see the effect doing much at all and if the wind changes direction you will lose even more.
Now I do realise it doesnt need wind to work but then you are also filling a humid house with more humidity, youll have a mosquito problem early morning and dusk ( not from the water but in general) and adding nets will slow down the airflow also.
I cant see a lowering of temps really to below ambient.
Has anyone done this and actually done recorded temps in Thailand in a humid climate with no mechanical aid and not with " it feels much cooler" type of responses.
Id be interested to know.
Im not being awkward am quite interested but struggle to see how this will get temps lower than ambient inside a house.
I can see how moving air will make you "feel" cooler but it doesnt lower the air temps in the house.
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Re: Passively Cooled House

Postby gliffaes » Wed Sep 19, 2012 2:56 pm

Sometimewoodworker wrote:
gliffaes wrote:and how long before the body of water heats up as temp variants arent that great here?


I think that there is a degree of misunderstanding here.

The water involved is not used as a heat sink. It is the energy involved in the change of state from liquid to gas that provides the cooling. This change uses a significant amount of energy which is why it is cooler near any body of water.

The trick is to channel the flow of air over the greatest area of water you can then direct that air into the places you want it.

Passive evaporative cooling would use things like the wind towers.
Active evaporative cooling use things like the mist spray, trickling water over a roof, artificial waterfalls etc.


FWIW (Fred translation :lol: For What It's Worth) there is research that shows that the difference between using cold (>5 deg C) and warm (<25 deg C) water makes almost no difference to the evaporative cooling effect. This is due to the great amount of energy required in the change of state from liquid to gas, compared to the energy neded to raise the temperature of the water by 20 deg C

http://heatisland2009.lbl.gov/docs/221000-narumi-doc.pdf is a very interesting study in Osaka City. the humidity in summer is very high. they got "whole-day average falling by 16.4°C" and a reduction in air conditioner energy use of 36%.


OK Ill go have a look at this to try and understand, i think our posts just crossed so maybe ignore what i said above
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Re: Passively Cooled House

Postby gliffaes » Wed Sep 19, 2012 3:00 pm

Oh I see your link is spraying water ( mechanical cooling) which i can see how it works but the pond by the house I cant see lowering to below ambient still?
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Re: Passively Cooled House

Postby Sometimewoodworker » Wed Sep 19, 2012 3:30 pm

gliffaes wrote:Oh I see your link is spraying water ( mechanical cooling) which i can see how it works but the pond by the house I cant see lowering to below ambient still?

It probably will not make a great difference. However when designed correctly lower than ambiant temps are not so difficult. Take a Look at Evaporative cooling.


All of this is still academic as the Original Poster doesn't seem to want to share any further information on his design.
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Re: Passively Cooled House

Postby fredlk » Wed Sep 19, 2012 3:34 pm

gliffaes wrote:But surely this then becomes mechanical cooling not passive as you have to pump the water to mist it using electric?

I'm having a swimming pool built anyway and its pump will be in use, but at the same time the overflow will run down a 2 metre high series of small rapids in the sun and this falling water will end up splashing, evaporating and getting caught in the wind. My pool will be mostly in the shade and so with evaporation, well-water replenishing and cooler nights, I'm hoping that it will not reach a temperature higher than 25 degrees. The 2 fishponds surrounding the houses and about 20 metres long will be totally in the shade and this water too should be no more than 25 or maybe 26 degrees and therefore cool the air around it a little as the wind blows over it.
gliffaes wrote:Far better for me to surround house with trees

Or vegetation as any of these give off evaporation.
gliffaes wrote:make sure slab is not in contact with sun

Better to have no slab at all. It only acts as a heat sink.
gliffaes wrote: build house on a hill

Check.
gliffaes wrote:orient house away from sun

Check.
gliffaes wrote:use light weight building materials

Check.
gliffaes wrote:When the wind stops blowing

It almost never stops blowing here.
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Re: Passively Cooled House

Postby Roger Ramjet » Wed Sep 19, 2012 3:38 pm

Even though the original poster has done a runner, I think the idea is correct under certain circumstances, however once the outside humidity is greater than a certain level it won't work. Which raises the fact that in Thailand where the humidity is high, we might have a problem. http://www.consumerenergycenter.org/hom ... ative.html
I recall at the Olympic Games in Sydney they had whole streets lined with fine evaporative coolers that the public and athletes used to walk through.
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Re: Passively Cooled House

Postby gliffaes » Wed Sep 19, 2012 3:42 pm

Roger Ramjet wrote:Even though the original poster has done a runner, I think the idea is correct under certain circumstances, however once the outside humidity is greater than a certain level it won't work. Which raises the fact that in Thailand where the humidity is high, we might have a problem. http://www.consumerenergycenter.org/hom ... ative.html
I recall at the Olympic Games in Sydney they had whole streets lined with fine evaporative coolers that the public and athletes used to walk through.


Yeah I heard those athletes were :lol: a bit soft
Talking of which where is that other northern athlete Geordie???

I hope the original poster posts his passive house info too??????
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