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In that case is AC still needed or would a dehumidifier be better to "cool down" a very humid house? I'm actually curious about the energetic efficiency of runn

In that case is AC still needed or would a dehumidifier be better to "cool down" a very humid house? I'm actually curious about the energetic efficiency of running a dehumidifier vs just turning on AC. AC has the advantage of outright lowering temperature while also dumping some of the humidity, but id guess not nearly as much as a dehumidifier. And if you are sweating at 78° it is probably so humid inside that just lowering temperatures ends up gets you very diminishing returns

endisneigh 5y ago
Most dehumidifiers generate heat. It would need to be a whole house dehumidifier which usually exhausts the hot air outside . A dehumidifier that keeps things cool is basically just air conditioning.
- analog31 5y ago
  Indeed, I've thought about a control for air conditioning, that's based on a combination of temperature and humidity, rather than temperature alone. I'm a northerner, and when I moved to Texas, I was prepared for the heat. What they didn't tell me about was the air conditioning. During the summer, people bring a sweater or jacket to restaurants because the AC is so cold. Today we live in Wisconsin, so we rarely use AC, usually only if we have elderly guests, or maybe the 1 or 2 most oppressive days of the year. We just have to manage the hours in the early evening, when the outside temperature has fallen but there's no breeze. So we have some window fans for that condition. But I've noticed, that I can turn on the AC and it will run for a long time without the temperature changing, because it's using all of its available power to remove water. But it gets more comfortable. But of course if you're going to cool the air in order to dehumidify it, you might as well enjoy the cooler air.
  - dragonwriter 5y ago
    > Indeed, I've thought about a control for air conditioning, that's based on a combination of temperature and humidity, rather than temperature alone. Better existing residential HVAC controls already do that, combining settings and sensors for dehumidfying, heating, cooling, and, if a humidifier is included in the system, humidifying.
- mardifoufs 5y ago
  Yeah I realized after typing my comment that I should've specified that I was thinking of whole house dehumidifiers but even then you are right, AC are basically dehumidifiers that also lower temperatures. But looking at the very high humidity levels in Houston, I'd think either people use normal sized AC units have no way to cope with so much humidity and lower it to a comfortable level or that Texans use very huge AC's which is not good for the grid. If it's option 1, I guess just adding more AC capacity would still be a better option than adding a whole house dehumidier? I guess I just expect there to be a more efficient way to cool a 78°F house to a degree where it's comfortable without having to use AC 24/7 but I guess the thermodynamics behind cooling homes disagree with me :').
  - vel0city 5y ago
    An AC unit is a whole house dehumidifier. A stand-alone humidifier is just a small AC unit where the cold side and the hot side are in the same room while an air conditioner splits those. The part that really pulls the water out of the air is the cold side. If you're wanting to pull moisture out of the air for a whole home, that unit is going to be an air conditioner unit.
yokaze 5y ago
There are ACs which have a dehumidifier mode, which according to the manual had less energy consumption.
toast0 5y ago
A dehumidifier is really just an air conditioner, cool the air so water condenses and collect that (and maybe pump it out), and then blow the hot air into the room, which also decreases relative humidity. If you only need to reduce humidity, like in a cool and humid basement, that's fine; the waste heat doesn't matter or may be helpful. If it's hot and humid, you don't really want the extra hot air, it's a lot better to run the heated working fluid outside, so you can dump the heat outdoors instead of indoors. Of course, an AC unit is often a lot bigger than a dehumidifier, and so all the rest of the energy use is bigger too, but if you could get a similar wattage system, putting the condenser outside the conditioned space means you get dehumidifying and cooling inside vs just dehumidifying, so why do only one.

endisneigh 5y ago

Most dehumidifiers generate heat. It would need to be a whole house dehumidifier which usually exhausts the hot air outside . A dehumidifier that keeps things cool is basically just air conditioning.

analog31 5y ago
Indeed, I've thought about a control for air conditioning, that's based on a combination of temperature and humidity, rather than temperature alone. I'm a northerner, and when I moved to Texas, I was prepared for the heat. What they didn't tell me about was the air conditioning. During the summer, people bring a sweater or jacket to restaurants because the AC is so cold. Today we live in Wisconsin, so we rarely use AC, usually only if we have elderly guests, or maybe the 1 or 2 most oppressive days of the year. We just have to manage the hours in the early evening, when the outside temperature has fallen but there's no breeze. So we have some window fans for that condition. But I've noticed, that I can turn on the AC and it will run for a long time without the temperature changing, because it's using all of its available power to remove water. But it gets more comfortable. But of course if you're going to cool the air in order to dehumidify it, you might as well enjoy the cooler air.
- dragonwriter 5y ago
  > Indeed, I've thought about a control for air conditioning, that's based on a combination of temperature and humidity, rather than temperature alone. Better existing residential HVAC controls already do that, combining settings and sensors for dehumidfying, heating, cooling, and, if a humidifier is included in the system, humidifying.
mardifoufs 5y ago
Yeah I realized after typing my comment that I should've specified that I was thinking of whole house dehumidifiers but even then you are right, AC are basically dehumidifiers that also lower temperatures. But looking at the very high humidity levels in Houston, I'd think either people use normal sized AC units have no way to cope with so much humidity and lower it to a comfortable level or that Texans use very huge AC's which is not good for the grid. If it's option 1, I guess just adding more AC capacity would still be a better option than adding a whole house dehumidier? I guess I just expect there to be a more efficient way to cool a 78°F house to a degree where it's comfortable without having to use AC 24/7 but I guess the thermodynamics behind cooling homes disagree with me :').
- vel0city 5y ago
  An AC unit is a whole house dehumidifier. A stand-alone humidifier is just a small AC unit where the cold side and the hot side are in the same room while an air conditioner splits those. The part that really pulls the water out of the air is the cold side. If you're wanting to pull moisture out of the air for a whole home, that unit is going to be an air conditioner unit.

yokaze 5y ago

There are ACs which have a dehumidifier mode, which according to the manual had less energy consumption.

toast0 5y ago

A dehumidifier is really just an air conditioner, cool the air so water condenses and collect that (and maybe pump it out), and then blow the hot air into the room, which also decreases relative humidity. If you only need to reduce humidity, like in a cool and humid basement, that's fine; the waste heat doesn't matter or may be helpful. If it's hot and humid, you don't really want the extra hot air, it's a lot better to run the heated working fluid outside, so you can dump the heat outdoors instead of indoors. Of course, an AC unit is often a lot bigger than a dehumidifier, and so all the rest of the energy use is bigger too, but if you could get a similar wattage system, putting the condenser outside the conditioned space means you get dehumidifying and cooling inside vs just dehumidifying, so why do only one.