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Using attic heat to cool a home?

05/03/2022 8:30 AM

Attics are hot in the summer,when we need the most energy to cool our homes.Would it be economically feasible to use Absorption cooling and/or heat tubes to use the attic heat to assist in cooling the home?Or heating in winter?

I do not know enough about either system to determine if it is possible.Both principles seem to be very simple at first glance,but is combining them for more efficiency possible?

Jus' thinkin'

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#1

Re: Using attic heat to cool a home?

05/03/2022 10:32 AM

It sounds like a good idea, theoretically. Here is a paper investigating that idea. You have to find a good heat sink on a hot day, (and it can't be inside the house!).

https://www.scirp.org/journal/paperinformation.aspx?paperid=97655

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#7

Re: Using attic heat to cool a home?

05/03/2022 4:23 PM

For a heat sink, I’ve read where they would have an enclosed pit filled with larger stones, so air circulates and passes through them, at night you would draw air from them that would heat your house at night, as the night rolls on, the stones would cool off that in the morning the stones would be cool you’d circulate the air and it would produce cool air…

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#2

Re: Using attic heat to cool a home?

05/03/2022 10:38 AM

It would be possible, but not practical in cost or performance...

https://www.sciencedirect.com/science/article/pii/S1110016820300375

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#3

Re: Using attic heat to cool a home?

05/03/2022 3:05 PM

Back in my younger years, I lived in the Caribbean. It rained seldom and there was a persistent water shortage. I was using a refrigerator that ran on propane.

One day while sitting at the bar contemplating the puddle around my beer can, it occurred to me that maybe solar heat concentrated with a magnifier could drive an absorption refrigerator to remove moisture from the air.

I never tried it out. It wasn't my refrigerator and besides, I needed it to keep food and beer cold.

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#5

Re: Using attic heat to cool a home?

05/03/2022 3:57 PM

It would work, but again probably not practical, you would still need to purify the water...better to just buy a watermaker...

Basically a dehumidifier, a water filter, and a mr coffee....

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#12

Re: Using attic heat to cool a home?

05/04/2022 9:05 AM

Yeah, the beers made it seem like a better idea...

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#13

Re: Using attic heat to cool a home?

05/04/2022 3:43 PM

Beware the beer goggles...

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#14

Re: Using attic heat to cool a home?

05/04/2022 5:34 PM

In my younger days… people questioned why I’d would just get out until after 10:00pm… because what they did realize is because that vision is a one way street…

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#15

Re: Using attic heat to cool a home?

05/04/2022 5:50 PM

Willy N knows exactly what you mean...

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#4

Re: Using attic heat to cool a home?

05/03/2022 3:44 PM

Ah ha , here you go, a true believer...uh don't ask how much it cost, or how reliable it is, or who can work on it when it breaks...and seriously don't ingest lithium bromide...

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#6

Re: Using attic heat to cool a home?

05/03/2022 4:18 PM
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#8

Re: Using attic heat to cool a home?

05/03/2022 5:11 PM

Of course, it's certainly possible to utilize excess attic heat for heating and/or cooling. One common example is the use of a ridge vent with soffit inlets. This passive system prevents stagnant, heated air from being trapped in an attic. Under the right conditions and location, a swamp cooler can utilize attic heat to cool.

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#9

Re: Using attic heat to cool a home?

05/04/2022 2:45 AM

Cheaper to just eliminate the heat...

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#10

Re: Using attic heat to cool a home?

05/04/2022 8:20 AM

I can see that almost anything is possible if you have the \$\$,such as earth source heat pumps,etc.A professor at a local college buried 600 linear feet of terracotta tile 10 feet deep,that terminated at his house.It exited 200 yards later with a vent cap -rain guard and screen.

The air entering was cooled by the tile underground to the soil temp of 55F and dehumidified by the cool pipe.The moisture drained out between the tiles,and the tile absorbed odors from the environment.The tile was surrounded by a layer of gravel 18"thick.The air from the tile was circulated though the normal house registers,and very little supplemental cooling or heating was required.

He oriented his house to capture the most solar heat in the winter,and shade trees to shade the house in the summer.The entire south wall was thermal pane glass,with an internal brick wall to hold heat.The entire foundation was poured concrete on 18 inched of gravel,with 12 inch flex pipe routed in it,through which the incoming air was circulated.The walls are double walls,2x6 and 2x4 with a gap in between through which the air is circulated,and in which the registers are mounted.

Very little energy required to heat and cool a 5000 square foot house.

A good idea,but expensive to implement.

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#23

Re: Using attic heat to cool a home?

05/06/2022 2:17 AM

Another direction is to cool a big lump of the ground (or a big water tank) when power is cheap at night and to use this for cooling. People have mostly done this for heat, sometimes solar heating stored "interseasonally" for the winter heating season for a whole settlement, but as the world heats up cooling is becoming a bigger issue. Would be good for big cities where the A/C fan boxes end up working against one another. India and Pakistan are getting it hard May 2022 with heat beyond 120F.

https://www.heatstore.eu/documents/HEATSTORE_UTES%20State%20of%20the%20Art_WP1_D1.1_Final_2019.04.26.pdf

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#11

Re: Using attic heat to cool a home?

05/04/2022 8:33 AM

After further research on the subject.,I discovered a contractor that claims money is better spent insulating the foundation of the house.His theory is that since hot air rises,the air in the attic can only heat the rooms through radiant heat,but heat from the floor will rise into the rooms.He insulates the foundation with duct pipe insulation,and uses r13 under the floors.R30 in the attic,and seals all outlet boxes for electrical,and the 1/2" gap at the bottom of the dry wall.Drywall is glued not screwed or nailed ..only enough fasteners to keep it in place as the glue dries.

The heat pump heats the domestic hot water for the home,and the exhaust from the dryer provides some heat humidity in the winter.

Sounds like a good idea to me.

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#24

Re: Using attic heat to cool a home?

05/06/2022 3:38 AM

Certainly the value of insulation varies with outdoor temp vs indoor temperature, the bigger the gap the more important the insulation...In the northern climes the difference between outdoor temp and comfort level indoor temperature can be 90°F , but in the southern climes the difference is quite a bit less, less than 20°F typically and 15° more commonly...On one hand you want to retain heat in the north, and on the other you want to block it in the south.. In the south the heat load majority is the roof, and secondly the windows and walls and air leakage, the slab is the least consideration...Up north keeping the floor warm becomes more important to the comfort level of the house....

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#16

Re: Using attic heat to cool a home?

05/04/2022 7:19 PM

In some mid-eastern locations with significant day/night temperature swings, some houses are built with a chimney near the high point of the room. It has a large cross-section and masonry walls about 8-10 inches thick. In the day, warm air in the room rises into the chimney where its cool mass cools the air so it falls back into the room as a gentle cool air movement. In the night, when the sun has warmed the chimney and the outside air is now cooler, the chimney warms air which rises through it to the outside, drawing cooler outside air in. This method is very old and works.

As HiTekRedneck said, you can bury a tube in the ground about 4' (1.3m) deep and at least 50-100 feet long. Bring it into the cold air return on the air handler. In the attic dedicate the space between a few rafters to air flow by putting a barrier on its under-side, opening it to the ridge vent at the top, and connecting its bottom to the room at the ceiling. During the day the air within it will heat up and go out at the ridge, drawing replacement air into the house through the tube buried in the ground.

Either of these use no energy source other than sun light and/or earth or air temperature.

--JMM

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#17

Re: Using attic heat to cool a home?

05/04/2022 7:33 PM

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#18

Re: Using attic heat to cool a home?

05/05/2022 4:42 PM

In some parts of the country a whole house fan can be used, usually about 4 feet in diameter, it's located in the middle of the house and draws cool air in from the open windows and exhausts the warmer air out into the attic which forces the hot attic air out the gable vents...the fan is so large so that it can turn at a slow rpm reducing noise...a lot of houses down south here have thermostatically controlled gable vent fans...I've installed several of these, they work well, typically combined with R-30 attic insulation, add reflective foil, and heat in the attic is just a memory..

Whole house fan...

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#19

Re: Using attic heat to cool a home?

05/05/2022 4:56 PM

A tee pee is a natural cooling effect no fans needed… so I’ve been told. ;)

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#20

Re: Using attic heat to cool a home?

05/05/2022 5:55 PM

There are a number of passive cooling designs, depending on the local climate conditions...

https://www.researchgate.net/figure/Types-of-passive-cooling-systems-3_fig4_265890843

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#26

Re: Using attic heat to cool a home?

05/06/2022 7:17 AM

MAN! That image brings back memories!

I went to the doctor and told him I kept having the same two dreams,night after night.

One night it was about wigwams,the next night it was tee pees.

Over and over.

He said I know your problem:

You are too tense.

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#25

Re: Using attic heat to cool a home?

05/06/2022 7:12 AM

Lots of older buildings have a copula of various shapes to help cooling.The Capital building in DC is one.

The Grand Master of passive cooling is the termite.They regulate the temperature within .5F degrees by design,with no electricity by using natural convection air currents.

They also use heat from decomposing waste to create a rising air flow from within in addition to outside Delta T.

Perhaps we should study them further for our designs.

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#27

Re: Using attic heat to cool a home?

05/06/2022 7:24 AM

A dome shape creates a lot of updraft,and Frank Lloyd Wright stated that a city,enclosed by a hemisphere of at least 5 miles diameter would float,the air weighing less than the standard building materials used inside ,depending on temperature,and that there would always be an updraft from the bottom to purge the stale air and cool it.I have not done the calculations,but if anyone wants to,I would be interested in the results. Small aircraft have to avoid flying too low above some domes because of the updraft.

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#21

Re: Using attic heat to cool a home?

05/05/2022 11:29 PM

Years ago I tried putting a bunch of black poly pipe on the roof of my house to heat water for my pool. It sort of worked, but the black pipe expanded and contracted so much that it would literally walk off my roof and I had to climb back up and push it back into place every week or so.

Then I came up with a much better idea--put heat exchangers in my attic and pump pool water through them. This would not only heat my pool, but cool my house! Thankfully, I came to my senses before I did this. Leaks would have been catastrophic, and the plumbing and heat exchangers would have been very heavy, possibly exceeding the load bearing capability of the rafters.

Thinking back, I still like the idea, but it would have to be in a house that was designed for such a system and with modern plumbing components (PEX, leak detection and shutoff systems, etc.).

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#22

Re: Using attic heat to cool a home?

05/06/2022 2:08 AM
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#28

Re: Using attic heat to cool a home?

05/06/2022 7:37 AM

I have often thought of using an in ground pool to help heat in the winter,by covering it with bubble wrap and extracting heat from the water.

I have not done the math on it,with for instance, a 20ft X 40Ft ft. and a 6ft. average depth,approx 40,000 gallons.The surrounding tile liner would also contribute to thermal mass from surrounding earth mass.

It probably would not work in some areas,but it may be a helpful contributor in others.

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#30

Re: Using attic heat to cool a home?

05/06/2022 5:02 PM

Wouldn't really contain enough heat to be useful...you would have to get the water temperature up near boiling to be efficient enough, and the tank would have to be sealed to prevent evaporation which would cool the water rapidly...so you would need concentrating solar collectors to approach that temperature, and a pump to circulate the fluid, probably better to go with oil as a fluid medium...already you've exceeded the cost of operating a conventional heating system...

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#29

Re: Using attic heat to cool a home?

05/06/2022 7:41 AM

Not sure if the above picture is NEC code compliant,as well as being too close to the pool,it is subject to damage very easily.However,it does make a good advertisement.

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#31

Re: Using attic heat to cool a home?

05/06/2022 8:45 PM

Those aren't solar electricity panels, those are solar water heating panels. No electricity involved except to pump the water. They came on the market long after I did my black pipe experiment.

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#32

Re: Using attic heat to cool a home?

05/10/2022 4:39 PM

You can now kill two birds with one stone.

You need hot water anyway...put in one of these.

You can duct the intake to this from your attic during the summer to greatly increase effeciency. It gives you hot water for far less energy than a standard unit. They pay for themselves in 4 years or so. They also exhaust cold air you can use to cool your house. During the winter you'll want to exhaust to the attic so a manual bypass damper would be handy.

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