The Revenge of the Circulating Fan

http://www.lowtechmagazine.com/2014/09/circulating-fans-air-conditioning.html

by lispython • 12 years ago

99 84 12 years ago

mturmon• 12 years ago

The five ceiling fans in my Southern California house are on virtually nonstop, night and day, from July through September. I haven't done analysis, but anecdotally they make rooms feel a lot cooler. If you get quality fans, they are inaudible (at low speed) and seem to be trouble-free (i.e., no problems after ~10 years of this level of activity).

jacquesm4• 12 years ago

Brushless AC motors (short circuit cage type) are extremely reliable, there are only two things that can happen: eventually the bearings will run out or the coils will short due to the mechanical friction resulting from the changing flux which tries to push the wire around. The stators are usually cast into a resin to counteract this as much as possible but in spite of that some freedom of movement usually remains.

kijin5• 12 years ago

Apart from a few isolated statements that suggest using fans together with ACs (which, of course, is a totally reasonable thing to do), the overall tone of the article is very much "AC = evil, fan = cool."

Unfortunately, fan-only cooling only works in a narrow range of climates.

For instance, instead of cooling down a space to 24°C (75°F), the aircon can cool it to 29°C (84°F), which is a comfortable temperature if combined with fans.

Whether or not 29°C can be considered a "comfortable temperature", even with fans, depends a lot on other factors, the most important of which is humidity. 29°C at 30% humidity is very different from 29°C at 90% humidity. The former is common in Europe and the American West. The latter is much more common in the Southeast, as well as the majority of newly industrialized countries such as China and India.

Try installing a radiant cooling system in one of those hot & humid places. See all that condensation on the walls? That's a recipe for explosive mold growth. All the fans in the world will not make that pesky H2O go away, since the air is already oversaturated with it. People can tolerate a lot of heat with nothing but a paper fan, but there's no alternative to a good ol' electron-guzzling compressor when it comes to humidity control.

You might feel totally comfortable with a fan in your cool and dry Northern California summers, but be very careful before you try to generalize your energy-saving hack to different climates. There's a reason why millions of people won't give up their AC's for fans, and it's not because they don't know how to stay cool.

macNchz• 12 years ago

Exactly. There could be an alternative discussion about the sustainability of cities that are entirely AC dependent, but the suggestion that AC is simply a luxury that could be largely replaced by fans gives me the impression that the author hasn't spent much time in Houston, Atlanta or Washington DC in the summertime. I don't like AC all that much, but I don't think I could continue to live and work in NYC in the summer without it, nevermind somewhere further south, it's just too damn humid.

Also, the author suggests leaving the air conditioning at a too-warm setting and supplementing it with fans...having experienced this as friends and family try to save money on cooling, I can't recommend it. At least with a typical residential HVAC system, it seems to me to make the air feel very stale, to where I'd much rather open a window even if it's sweltering outside.

kijin5• 12 years ago

HVAC systems should only circulate dry air. When they circulate lukewarm (read: insufficiently dehumidified) air, various smelly and unhealthy substances tend to accumulate in the ducts and filters. Stale air is a telltale sign that you've got a mycotoxin factory in your house.

cafard• 12 years ago

I have made it through a number of Washington summers simply on fans. Now, I was in a deeply shaded neighborhood, and to be sure I did not sleep that well on the hot nights. I wouldn't do it now: for one thing, my wife would regard it as insane.

The problem that occurs to from NYC is the noise that would come in through open windows.

antimagic2• 12 years ago

False dichotomy. Fans can be used in conjunction with AC, greatly reducing the energy required by the AC, by making higher temperatures acceptable.

kijin5• 12 years ago

Of course it's a false dichotomy. Did you read the first sentence of my comment?

linuskendall4• 12 years ago

I've lived in India for years, generally my experience has been that fans work much better in humid air than dry air. So 29 degrees with 90% humidity and fan would be much more comfortable than 29 degrees with 30% humidity and fan.

In Delhi (45 degrees in summer) we would manage with desert coolers + fan, which specifically work by increasing the humidity of the air and then using a fan.

I believe though that, AC vs. coolers vs. fans vs. any combination of them is really not at all as important as the way cities and the buildings within them are built. In Delhi it is estimated that 3-5 degrees local heating is caused by bad urban design. As an anecdote, I've been in mud-huts where despite 45 degree temperatures outside, insides felt like they were AC. Sure, mud-huts do have problems with mould and require a lot of maintenance, but it's illustrative that we've dug ourselves into a hole where AC is required because we build buildings of inappropriate materials.

lutusp• 12 years ago

In Delhi (45 degrees in summer) ...

That's 113 degrees Fahrenheit for American readers. The rest of the world has wisely adopted more rational measurement units. Even Canada, a stone's throw away from the U.S., uses the Metric system.

kijin5• 12 years ago

Sure, mud-huts do have problems with mould

Yeah, mold tends to be the default trade-off when you choose any method of cooling other than AC.

As someone who is allergic to mold, I'd choose an air-conditioned glass-and-steel box any day over a moldy mud hut if they were equally cool. But I do wonder if, given better technology, we could come up with buildings and cities that have the best of both worlds.

Maybe we should look to ancient building materials and methods for new ideas. The Seokguram grotto in Korea, for example, had been dry for over a thousand years until modern "restoration" projects messed up the delicate balance of air and water. Now there are dehumidifiers running 24/7 to keep mold out of the grotto. It's really pathetic. If pre-modern Indian mud huts can reduce the temperature by 10 degrees without electricity, why can't modern science come up with structures that reduce the humidity by 30 percent, for instance?

mcguire3• 12 years ago

"desert coolers + fan, which specifically work by increasing the humidity of the air and then using a fan"

Actually, evaporative coolers significantly reduce the air temperature[1], when used in dry climates.

[1] http://en.wikipedia.org/wiki/Evaporative_cooler#Performance

"At 32 °C (90 °F) and 50% relative humidity, air may be cooled to about 24 °C (75 °F). The dew point for these conditions is 20 °C (68 °F).

"At 40 °C (104 °F) and 15% relative humidity, air may be cooled to nearly 21 °C (70 °F). The dew point for these conditions is 8 °C (46 °F)."

eclipxe• 12 years ago

The first fan pic in the article - the Big Ass Fan Haiku - awesome fan with lots of tech

jrapdx3• 12 years ago

No question ceiling (and other) fans are useful for cooling, also for heating by distributing warm air that otherwise pools overhead, especially in high-ceiling rooms.

A cool water radiant system certainly seems it would save electric power. But I wonder if such use of water is potentially a problem in regions where water is a precious commodity.

Growing up in the desert of Arizona in the era before air conditioning became widespread, there were interesting approaches to dealing with summer heat. Relevant here, the "swamp cooler" was a fixture in most homes.

Sort of a combination of moving air and water methods, the cooler worked by running a squirrel cage fan in a slatted metal box and water dripped through material mounted on the interior box surface. Air flowed through the openings in the box, evaporating water and cooling the stream of air which was piped into the house though metal ducting.

This worked great when the air is dry. The later summer monsoon season was its ruin: high humidity did not favor evaporation, or much cooling at all. It was enough to make people think air conditioning would be a really good thing.

cornewut• 12 years ago

The article mentions that fans don't work when air temperature is higher than that of the skin(35C).

This actually is not correct as increased air flow facilitates evaporation (making sweating more effective).

kijin5• 12 years ago

Only if humidity is low enough.

Otherwise, moisture from the air will condense on your skin (making sweating completely ineffective).

rurounijones• 12 years ago

Helloooo Japanese summers.

qwerta• 12 years ago

Other option is to go underground. On continental climate it also saves winter heating costs

girzel4• 12 years ago

Why isn't this considered as a solution more often? Is it just because construction costs go up, or for reasons of culture and habit? It seems like this is absolutely the best approach for stabilizing temperatures in both hot and cold climates. Might not work well in a place with a lot of ground water, I guess, but in general it seems like a win. Reduces building profiles, as well.

rprospero• 12 years ago

While I've read enough Asimov to believe that the future is underground, I'll also be the first to admit that the lack of windows is a major problem with the system. You both lose natural light and the cooling air currents provided by the wind.

seanmcdirmid• 12 years ago

We like our views. Also, fire code wouldn't really allow for it in most developed countries...sinking windows is quite expensive.

pcrh2• 12 years ago

A traditional Persian method of cooling was to build windcatchers combined with an underground intake that was routed underground where it cooled.

https://en.wikipedia.org/wiki/File:Qanat_wind_tower.svg

jessaustin2• 12 years ago

That seems like a great idea if you happen to build near a functional qanat. It's irrelevant to 99.9% of the locations where humans build homes.

carlob• 12 years ago

I think another solution that is often overlooked in the US is the passive flow caused by open windows. I've been to so many buildings in the US where it's impossible to have windows wide open and in some cases open at all.

I tend to think this is a bit like suburbia: a design choice made when energy was much cheaper.

ZeroGravitas• 12 years ago

The article also suggests this is due to comfort regulations about airflow, which were originated by the heating and cooling industry and so are not likely to be friendly to methods that don't involve their products.

pimlottc• 12 years ago

I've heard some fascinating stuff about passive airflow architecture. The floor plans of old buildings were often laid out in very specific and sophisticated arrangements designed to take advantage of local prevailing winds and weather patterns so that opening certain pairs of windows at certain times of day would effectively ventilate the entire structure. It's interesting to also think of the secondary effects we've lost by effectively sealing out the outside world and living in a closed box.

girzel4• 12 years ago

I would love to read a book on this: How far can you get relying purely on design and structure, not technology. "Passive" solutions, as you say. A fascinating topic.

mogrim• 12 years ago

Lincoln Castle prison (in the UK) used passive cooling, there's a Time Team documentary about it - the jail fever outbreak section talks about it:

https://www.youtube.com/watch?v=Pm6A9sNXnzw#t=2013

(The entire documentary is fascinating, assuming you like archaeology / history of course!).

JeremyNT• 12 years ago

When we visited the island of Vieques, Puerto Rico, we stayed at the Hix Island House[0]. This facility is marketed as being "green" in general and all of the suites are cooled exclusively by wind.

This is easy to accomplish at their location due to a prevailing wind from a predictable direction. There aren't really "windows" in the building at all - rather there are two garage doors at opposite sides of the suite which can be opened to allow the wind to flow through the entire building unimpeded.

We went at the height of summer when humidity was very high and daytime highs were > 90F, and we never found it uncomfortable. And despite large numbers of insects on the island, the strength of this wind was adequate to keep them from bothering us.

The truth however is that this technique is very region specific. Windows are less effective in areas with less wind, obviously, and in areas where the wind doesn't flow in a consistent direction it can be more difficult to implement a design to accommodate this fact.

Adding fans can supplement this technique in areas with less wind. However, if you have high humidity as well as high heat, a small breeze is unlikely to be adequate; you need to move a lot of air if it's both hot and humid. While the Hix House design worked well in PR, I am sure that the typically calm, humid, hot air I encounter in a southern summer would be far less comfortable.

At my own southern home, built in the 1920s and long before suburbia and the rise of residential air conditioning, we have windows on all sides as well as ceiling fans. However, I cannot approach the comfort level I experienced in PR at similar heat and humidity levels - without, of course, turning on my air conditioning.

[0] http://hixislandhouse.com/

vonmoltke• 12 years ago

That basic design is common in southern Florida and the Caribbean. The Florida-style house has a central breezeway, which is basically an unobstructed path from the front wall to the back wall. The front wall has a large bank of awning windows, while the back wall typically has a multi-panel sliding glass door. When both are open, it creates a draft through the house that not only cools the breezeway but also the other rooms.

callesgg2• 12 years ago

    "AC accounts for approximately 20% of year-round electricity consumption
    by American households, and 15% of total electricity use. [1] The widespread
    use of AC explains in large part why Americans use so much more electricity
    than Europeans: AC electricity use by an American household equals 60% of
    all electricity used by the average European household. [2]"

That math with that statment does not realy work.

vinw• 12 years ago

I think it can hold together if there is a lot of non-domestic AC use in the US.

nyc640• 12 years ago

I think it means..

  American Household : [XXXXXX------------------------]

  European Household : [----------]

Where the X's are electricity usage by American households on air conditioning (20% of total electricity use), which is equal to 60% of all electricity used by a European household.

TeMPOraL• 12 years ago

Comparing this to jacquesm's excellent and detailed explanation I have to admit that sometimes a simple picture can really be worth a thousand words.

callesgg2• 12 years ago

Yep ;)

DamnYuppie2• 12 years ago

Europe is also much cooler then most of the USA in the summer. You all are welcome to come and hangout in the south any summer you want, then you will have a better understanding of the AC usage here. If I lived in Europe I probably wouldn't need AC either.

jacquesm4• 12 years ago

It does actually. I think I see where you think it does not work but European homes are also smaller and in general more energy efficient. So consumption overall is a small fraction of what an equivalent household in the US would spend.

A large factor in that is that energy prices here are substantially higher per unit than in the US.

To break that statement down:

- AC acounts for approximately 20% of year-round electricity consumption by American households

So when looking at the average household electricity bill 20% of that consumption will be on account of AC

- and 15% of total electricity use.

That's if you factor in all other uses besides household (so including offices and factories, and offices also use AC so that's why the percentage didn't drop that much).

- The widespread use of AC explains in large part why Americans use so much more electricity than Europeans: AC electricity use by an American household equals 60% of all electricity used by the average European household.

Taking the total consumption of the average European household and comparing that to the US electricity bill the AC consumption portion of the American household is already equal to 60% of the EU total household consumption.

So if the EU household consumes 100KWh (just a number) the US household will expend 60KWh on AC, for a total consumption of about 300KWh. So three times as much total consumption. Just by cutting the AC component out that would drop to 2.4 times as much. The remainder can be explained by differences in area, more energy efficient appliances, less electric heat (very rare in the EU, baseboard heating is very normal in the US) and in general a more energy consumption conscious lifestyle because of the higher energy prices.

mrfusion2• 12 years ago

Has anyone installed a whole house fan? I've heard they can rapidly cool your house to the outside temp at night?

I can't decide if it would hurt resale value too much to have a giant fan vent in the middle of the ceiling though.

kd0amg2• 12 years ago

My apartment has one, but it's too loud to run it overnight. The vent itself doesn't seem like a big deal though. It falls shut when the fan isn't in use.

mrfusion2• 12 years ago

Can it cool down your place really fast? For example in my house, when it's 80 degrees inside and 65 outside, I can open all the windows, and it gets down to 75 overnight :-(

brixon• 12 years ago

It has louvers so when the fan is off it is not visible.

We had on when I was a kid. It is much cheaper than box fans in every window and more aesthetic.

agarden• 12 years ago

I lived in a house where one was installed. It could cool down the whole house in half an hour. Operation was noisy.

craftsman• 12 years ago

We've got a whole house fan and it's awesome. We live in a climate that cools off nicely at night and it works like a charm.

We do run the AC for a few hours on really hot days to 'cut the top off' of the heat, but at night the whole house fan comes on. We can then go a large part of a really hot day by managing shades and windows and the house stays nicely cool.

chiph• 12 years ago

I grew up in a house that had one.

Pros: Really effective at temps below 95F; Way cheaper to run than central air (but variable flow mini-splits might be closer).

Cons: Noisy; Sucked in dirt & dust from outside; The closed metal louvers didn't provide any insulation in the winter (so we had to put an insulated box over it); Didn't help much when humidity was sky-high.

Might be a good option for overnight cooling in a house with battery-backed solar (would have to run the numbers to see).

weaksauce• 12 years ago

Yes. They are great for certain sized homes. They can cool off a house pretty quickly in the evening provided it's cool outside. Installed with whirlybirds on the roof and it also provides the benefit of pushing out the blanket of hot air in your attic to keep temps down... The only cons are how loud it is and the fact that it's uninsullated.

mcguire3• 12 years ago

Keep in mind that (courtesy of the (aeronautical) engineer buddy o' mine) one of the, if not the primary, costs of air conditioning is condensing water out of the air in even moderate humidity.

If you open your house to the outside at night when it is cool enough, you may be allowing moisture into the house which will cost you more during the day when the AC is running.

Note: your mileage may vary.

bmm6o• 12 years ago

We had one when I was a kid. It really moves the air through the house and can be effective in the right circumstances. Also, it's awesome to fly paper airplanes into.

a2tech• 12 years ago

As someone that lives in a house built in 1860 (so windows open to allow passive airflow) that has been retrofitted with ceiling fans and AC I can tell you that if you're in a region with any sort of humidity that AC is unbeatable. The ceiling fan is great if its slightly warm, not humid, and you have the windows open.

ferongr• 12 years ago

I don't know, I can't say I agree with the article. I grew up (and still live) in a small apartment in Greece. My family had fans (because air-conditioning was expensive back in the day) all around the house. We "managed", but it was definitely not comfortable when ambient temperature increased above 32C. After installing air-conditioning (3 12000 BTU ductless mini-splits) everything changed. Summers were finally comfortable afterwards and today I would never think of decommissioning the A/C units, regardless of electricity costs.

papercrane• 12 years ago

Article says the limit of this is 30C. I don't think the argument here is that fans can replace all uses of AC, but rather can supplement them.

CanSpice• 12 years ago

The article makes the point that A/C in conjunction with fans can reduce the amount of energy needed to reach the same comfort levels. You don't need to remove the A/C if you install fans, but you can set the A/C thermostat to a higher temperature (which saves on electricity use and cost) and turn on a fan to get the same comfort level.

jrkatz• 12 years ago

I live on the first floor of a house in Boston, and this summer made it through without AC. By keeping heavy curtains drawn and closing both layers of the double windows during the day, then opening windows at night and using fans to draw cooler air through the apartment, I was able to keep the apartment relatively cool throughout the summer.

Sure, there were nights my apartment still hit 87F indoors by the time I was going to bed -- a week of nights that don't dip below 80 will do that -- but it doesn't take that long to get used to it and the breeze from open windows and running fans made it much more tolerable.

There are a lot of places in the US that benefit tremendously from AC -- I grew up in the Mojave desert and there is little arguing with AC at 110F -- nonetheless the the machines are overused. If more people decided to tolerate 80F as room temperature, even without active measures to replace AC in their homes, we'd see a precipitous decline in energy usage. Add to that careful control of airflow and insulation and many regions simply don't need AC.

Meanwhile, I am at my office, and the AC is run so high in the summer that many people wear jackets indoors year round here. Lovely.

benologist• 12 years ago

I grew up in Australia, our summers were also in the 80 - 110 range and if we wanted AC that meant going to the mall.

300bps• 12 years ago

the machines are overused. If more people decided to tolerate 80F as room temperature...we'd see a precipitous decline in energy usage

When I first moved into my current house I was setting the air conditioning at 78 degrees. Then I had my central AC unit serviced and the tech showed me little dots of mold throughout the inside of the unit in the basement. He told me not to set the thermostat above 75 degrees in the summer time because it doesn't get enough humidity out of the air. He also said to make sure I kept a dehumidifier running in the basement.

Now I keep the thermostat on 75 and keep the basement at 50% relative humidity using a dehumidifier in the summer. I also ended up installing a UV light inside the basement unit myself to kill microorganisms.

So it's easy to say to just tolerate higher temperature but the unfortunate thing is that high humidity levels inside a home can lead to serious issues.

kingmanaz• 12 years ago

The Bonelli house in Kingman, Arizona was built before central air conditioning became common in homes. Temperatures in Kingman regularly reach > 110F (43C) in the summer, yet the Bonelli house was comfortable without air conditioning or fans. To cool the house, a trap door in the center of the first floor was opened, drafting cool air from the deep, unfinished basement, through the intervening floors, and out a roof cupola. The system was passive and still functions today.

http://kingmanhistoricdistrict.com/homes/bonelli-house/index...

Other locals would hang burlap or bedsheets over open windows, periodically dampening the material with a hose. The hot breezes would blow through the wet material, evaporating the moisture, and cooling the air. Many older homes still have the blanket hooks above windows, though residents have long since switched to air conditioners or swamp coolers for cooling.

ScottBurson• 12 years ago

If anyone is looking for a product recommendation, permit me to suggest the Fanimation Landan [0]. My wife and I have one in the living room and love it. 6 speeds, remote control, LED lights built in (dimmable using the remote), efficient DC motor.

[0] http://www.fanimation.com/products/landan/

pnathan• 12 years ago

I've lived with box fans for years. This is our second summer in the Pacific Northwest, and our current apartment has no air movement. I.e., you can have box fans in the windows all night, and the kitchen is this mass of warm air when you get up. The apartment heats up very quickly and loses heat slowly for some reason. The apartment quickly reaches 78-80 degrees and is really unpleasant. So this summer indicated an AC purchase for the bedroom was a good idea. It's been extremely nice to sleep in a cool & dry room.

I'd be quite happy to have a residence that had decent air movement design, along with ceiling fans, but I don't think I'm giving up the bedroom AC.

kazinator• 12 years ago

[Fans] can only provide cooling at air temperatures below the mean skin temperature, which is about 35°C (95°F). Fans cannot cool people above that treshold, because moving air cannot reduce the skin temperature below the ambient temperature – no matter how high the air speed.

The statement applies to passive heat sinks. If a device's heat sink has a surface temperature of 35°C, then blowing 40°C air across it faster will not only help, but it will be counterproductive: the warmer air heats the heat-sink, and moving air does it faster.

In 40°C relatively dry air, your skin is 35°C only because of active heat removal: evaporation. This changes the picture. Moving air can speed this up even though it is warmer. If the air doesn't move, then evaporation wraps you in a blanket of humid air. Ventilation displaces the humid air, replacing it with dry air that can take up moisture.

The Revenge of the Circulating Fan

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