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Comment by GeekyBear | Hacker News Reader

I had family members who lived in a home in the deep south that was built before air conditioning was common. It had a large fan in the ceiling of a central hallway that vented the air from the inside the house out through the attic. This was an industrial grade fan that moved a huge volume of air.

At bedtime, they could open the bedroom windows and turn on the fan and a stiff wind would blow in through all the bedroom windows in the house.

That fan, along with window awnings and tall ceilings, really made a difference in how often they needed to use air conditioning, even near the Gulf of Mexico.

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We had a whole-house fan like this in Sacramento. It worked especially well there because (1) it was not humid, and (2) the temperature at night was much lower than in the daytime. It might be 100° during the day, but it would be in the 60s at night.

Fans like this aren't nearly as effective if either of these conditions is not met — then you're just pulling in air that is somewhat less uncomfortable each night, instead of getting truly refreshed.

As mentioned, this was right on the Gulf of Mexico where it was both very hot in the day and very humid all the time.

In the early summer, the temperature dropped from the upper 90's in the day to the low 70s at night. In the worst of the summer, the temperatures were only dropping to the 80's, and they did use the air conditioners then.

However, that fan moved so much air that there would be a stiff wind blowing across the beds all night, and that cool humid wind would have you under the blankets in no time.

I.have one in my house, it is going to be removed in the near future. It works good some days, but modern ac is still better. When we use the ac it lets hot air from the attic in, and worse all winter it is letting cold air from the attic in. The thing can really be insulated.

There is a lot about this house that needs to be updated to modern energy standards and getting rid of that fan is on the list. Overall it costs far more than it saves.

>When we use the ac it lets hot air from the attic in, and worse all winter it is letting cold air from the attic in.

The one in my relative's house had louvers that would open when you turned the fan on and then close when you turned it off, so it sealed itself off when not in use.

They saved a fortune by not having to run the ac all summer.

Those louvers don't seal very well at best, and even sealed they have no r value so they are not very useful. They can save ac in summer, but IMO not enough

Actually, they did seal well, and the savings were quite significant.

I installed a whole-house fan in our place in San Jose. That plus ceiling fans in each bedroom meant we could go all year without A/C. This was the Bay Area though.

I had remembered whole-house fans when growing up in Kansas — many of my friends had homes with them. They could be noisy but really did make for a nice house breeze in the evening.

My childhood home, in a mid-century California suburb, used the same fan arrangement. Incredibly effective... if also very noisy.

what state and what was the average humidity, or even better dew point?

I personally find fans made very little difference for me in humid climates.

Fans don't improve comfort as much if humidity is high, because the airflow doesn't cause as much evaporative cooling on the skin. So you need a temperature gradient to get a good effect. Attic fans are a good example. The attic tends to get hotter than the outside air when the sun is shining, and the fan helps equalize.

GP and GGP are describing different methods of cooling:

Sitting in a breeze does two things: 1) Allows your sweat to evaporate more quickly, and that evaporation is what causes most of the cooling effect. It's not very effective in high humidity because your sweat won't evaporate very easily. Evaporative coolers / swamp coolers work off this same principle. 2) Sitting in the still indoor air your body heat warms the air around yourself and you end up sitting in that pocket of heat. Just about any airflow stops that, which is why air circulators (fans that are meant to point from one end of a room to another instead of directly on a person) work to make a room feel a bit cooler.

Running the attic fan at night with open windows can have similar effects as above (especially the air circulator), but on top of that it's for pulling in the air from outdoors after it's cooled off at night, and expelling the warmed-up air that accumulates near the ceilings and roof. You'd want to close windows in the morning so the warmed-up air doesn't get pulled in and replace all the cooler air.

There are air conditioning robots that follow a person around blowing cold air on them.

They aren’t very practical, but could be more efficient than cooling an entire building for one person.

And instead of cubicles, perhaps we could have insulated ice baths like athletes use after games. You sit down in there and pull a tray over the bath with your keyboard, mouse and monitor. You can soak your hands to keep the inflammation down from the repetitive stress too.

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