Using sub floor air for cooling?

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Re: Using sub floor air for cooling?

Postby pauljuzza » Tue Mar 16, 2010 3:39 am

All cooling is forced air. The underfloor space is usedly solely as a plenum.
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Re: Using sub floor air for cooling?

Postby sealbasher » Sun Jul 11, 2010 1:10 am

Hi All
I hope someone can help me with this. I actually have my flat roof home on stumps, in recent renovation that area renovated has about 1400mm clearance from ground. I installed two 5000l bladders to collect rainwater. Someone mentioned a bladder to use as heat exchanger. I am wondering how i could achieve this. I would either pump air thru an exchanger or use some sort of drip system to cool the air as well. I live in Adelaide so hot and dry, but under the house is definitely cooler and the rainwater in the bladders is very cool. I would defintely like to use this to cool my house, but do not know how best to proceed. Any thoughts?
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Re: Using sub floor air for cooling?

Postby Gordon-Loomberah » Sun Jul 11, 2010 9:05 pm

If you are going to try to dump heat from the house into the water filled bladders, you need to be very careful about how much heat you try to put in there... I notice on my 22000l poly tanks that they are only rated for 23C. Not sure what your bladders are made of, but its worth checking their max operating temperature.

If you are thinking about some sort of drip system to cool the air by evaporation, its probably easier just to buy a swamp cooler and use that water to run them... unless it tastes better than tap water, in which case, drink it and use the tap water for the cooler ;)
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Re: Using sub floor air for cooling?

Postby sealbasher » Sun Jul 11, 2010 9:14 pm

Thanks for the reply Gordon and good point. What is a swamp cooler though, and where could i buy one from?
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Re: Using sub floor air for cooling?

Postby Gordon-Loomberah » Sun Jul 11, 2010 9:22 pm

Swamp cooler = evaporative cooler ;)
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Re: Using sub floor air for cooling?

Postby gully » Fri Jul 16, 2010 3:34 pm

sealbasher wrote:Hi All
I would either pump air thru an exchanger or use some sort of drip system to cool the air as well. I live in Adelaide so hot and dry, but under the house is definitely cooler and the rainwater in the bladders is very cool. I would defintely like to use this to cool my house, but do not know how best to proceed. Any thoughts?
alan


I may be wrong but (reverse) hydronics? pump cold water through hydronic radiators to cool the rooms?
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Re: Using sub floor air for cooling?

Postby Gordon-Loomberah » Fri Jul 16, 2010 6:48 pm

gully wrote: I may be wrong but (reverse) hydronics? pump cold water through hydronic radiators to cool the rooms?


2 Problems:
1/If the water is only a few degrees below the air temperature, there will be bugger all cooling happening... try heating a 20 degree room with 25 degree water in a hydronics system. Slightly warm to sit on, but thats about it. The temperature difference needs to be much greater.

...which brings me to:

2/ If the water being circulated is cold enough to cool the room, it's probably below the dew point of the air, so water will be continually condensing on, and drpping off the hydronics radiators onto the floor.
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Re: Using sub floor air for cooling?

Postby gully » Sat Jul 17, 2010 5:58 pm

Gordon-Loomberah wrote:1/If the water is only a few degrees below the air temperature, there will be bugger all cooling happening... try heating a 20 degree room with 25 degree water in a hydronics system.


Fair enough... I would've thought there'd be at least 10-15 degrees difference but yeah 5 degrees is bugger all. Efficiency would have to be up near 80% or higher to bother. Another problem is that without forcing air circulation you'd end up with cold spots in the room. I imagine normal hydronics suffers from this also.

Gordon-Loomberah wrote:2/ If the water being circulated is cold enough to cool the room, it's probably below the dew point of the air, so water will be continually condensing on, and drpping off the hydronics radiators onto the floor.


Depends upon humidity a la evap coolers. In anything that cools you will have this problem cooling air so eventually you need a dehumidifier... then you get the dry cold air air-con is known for :)
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Re: Using sub floor air for cooling?

Postby lad » Tue Sep 20, 2011 3:10 pm

gully wrote: Another problem is that without forcing air circulation you'd end up with cold spots in the room. I imagine normal hydronics suffers from this also.



Hydronic heating relies on cool air at floor level being drawn over the radiator and causing an updraft. This air flow then disturbs the air in the room, spreading the heat. The radiator also radiates heat as infra red energy out into the room.

it is certainly warmer right next to the radiator, but in a well organised setup, the room is roughly evenly heated.

To achieve a similar result, you would need to ceiling mount radiator panels for cooling and if the differential between room temp and water temp is not great enough, then little cooling would be achieved.
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Re: Using sub floor air for cooling?

Postby jarbar » Tue Sep 20, 2011 5:43 pm

Using underfloor cooling definitely makes a difference at our house.I disconnect the return air duct from the ducted heating at the start of summer.(I have been intending to make a movable baffle but health has impeded this thus far). Except on the hottest of days air from under the house is cooler than that inside,and as it pressurizes out through the floor vents and escapes into the wall vents near ceiling height also causes some positive air flow into the roof space,reducing radiated heat into ceilings from tiles.

I have also installed a ceiling fan inside the roof space which displaces some of the previously static hot air through gaps in tiles.Solar panels also reduce considerably the radiant heat from the previously uncovered North roof.Rarely does our refrigerated AC get turned on and when it does has far less work to do.And as for those incredibly noisy swampy's, my neighbors have them ,I hate them.I finally managed after much argument to get the EPA to have one moved on a medical clinic behind us last summer.Hurray some peace at last.!!! :lol:

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