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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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.
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.
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.
"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]"
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.
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.
> [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.
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.
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.
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.
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.
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).
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.
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.
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.
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.
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.
[+] [-] kijin|11 years ago|reply
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|11 years ago|reply
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.
[+] [-] linuskendall|11 years ago|reply
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.
[+] [-] antimagic|11 years ago|reply
[+] [-] jrkatz|11 years ago|reply
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.
[+] [-] 300bps|11 years ago|reply
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.
[+] [-] benologist|11 years ago|reply
[+] [-] jrapdx3|11 years ago|reply
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.
[+] [-] carlob|11 years ago|reply
I tend to think this is a bit like suburbia: a design choice made when energy was much cheaper.
[+] [-] JeremyNT|11 years ago|reply
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/
[+] [-] pimlottc|11 years ago|reply
[+] [-] ZeroGravitas|11 years ago|reply
[+] [-] mturmon|11 years ago|reply
[+] [-] jacquesm|11 years ago|reply
[+] [-] ferongr|11 years ago|reply
[+] [-] papercrane|11 years ago|reply
[+] [-] CanSpice|11 years ago|reply
[+] [-] kingmanaz|11 years ago|reply
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.
[+] [-] cornewut|11 years ago|reply
This actually is not correct as increased air flow facilitates evaporation (making sweating more effective).
[+] [-] kijin|11 years ago|reply
Otherwise, moisture from the air will condense on your skin (making sweating completely ineffective).
[+] [-] callesgg|11 years ago|reply
[+] [-] nyc640|11 years ago|reply
[+] [-] jacquesm|11 years ago|reply
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.
[+] [-] vinw|11 years ago|reply
[+] [-] kazinator|11 years ago|reply
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.
[+] [-] pnathan|11 years ago|reply
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.
[+] [-] ScottBurson|11 years ago|reply
[0] http://www.fanimation.com/products/landan/
[+] [-] a2tech|11 years ago|reply
[+] [-] eclipxe|11 years ago|reply
[+] [-] mrfusion|11 years ago|reply
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.
[+] [-] craftsman|11 years ago|reply
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|11 years ago|reply
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).
[+] [-] mcguire|11 years ago|reply
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.
[+] [-] weaksauce|11 years ago|reply
[+] [-] agarden|11 years ago|reply
[+] [-] bmm6o|11 years ago|reply
[+] [-] kd0amg|11 years ago|reply
[+] [-] brixon|11 years ago|reply
We had on when I was a kid. It is much cheaper than box fans in every window and more aesthetic.
[+] [-] qwerta|11 years ago|reply
[+] [-] pcrh|11 years ago|reply
https://en.wikipedia.org/wiki/File:Qanat_wind_tower.svg
[+] [-] girzel|11 years ago|reply