Anyone used a dehumidifier to reduce AC use?
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  1. #1
    Registered User warramra's Avatar
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    Default Anyone used a dehumidifier to reduce AC use?

    We live in the SE US, land of high summer humidity. I find myself using the AC more due to rising humidity levels rather than due to the heat. I've semi-looked at buying a dehumidifier to use in our main living area, thinking that we would not need to turn on the AC as much. But, dehumidifiers send drier, yet warmer back out and I am not sure if that wouldn't defeat the purpose. Plus, they run all day sucking electricity.

    Has anybody used dehumidifiers? How effective are they in a large, open living space? Does the electricity used defeat the purpose of trying not to use the AC?

    TIA
    Amy

    Wife to one hardworking man
    Homeschooling mom
    Three girls 14,11 & 9
    one boy 7

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    We've used dehumidifiers for many years, and they are placed in the basement (our home is 3-yr old, 1372 sq. ft.). Our daughter, who doesn't have a basement, puts her's in her laundry room or kitchen. Choose a dehumidifier that is the appropriate for the size of your home, and there are also Energy Star models (which we have). We also got a tax break by choosing the Energy Star model.

    Our A/C technician said he cut his parent's bill in half by convincing them to just LEAVE the A/C on - even if they turned the temperature warmer and added fans in the evening, it kept the humidity under control.

    Here's what's happening... When people open the windows of their homes in the evening because it's in the 70's and the humidity goes up to 89% or higher overnight, then turn their air conditioner on in the afternoon, the air conditioner actually spends all that time removing humidity (conditioning the air), NOT cooling, only to have it turned off again in the evening. It doesn't work efficiently until it alters that dew point temperature in the house - the amount of moisture in the air to the air temperature.

    You need to figure your dew point temperature outside so you know if it's more economical to leave the air conditioner on.

    "The dew point is the day-to-day measure of humidity in the atmosphere. Another critical measure is the "design dew point" -- the maximum humidity level at which air-conditioning systems can operate efficiently in different regions."

    "The dew point temperature is defined as the temperature of the air when the relative humidity is 100 percent. Relative humidity is defined as the amount of moisture in the air relative to the most moisture the air can hold at the same temperature. As air is cooled it loses its ability to hold moisture. So, relative humidity is increased by cooling the air, as well as by adding moisture to it. For example, as the air cools on a muggy night the relative humidity increases. When the relative humidity reaches 100%, the air has been cooled to its dew point and dew forms on surfaces."

    "Similarly for the air conditioner, once the air is cooled below the dew point, the air releases moisture which collects in a drain pan, and drains out of the system. The cooled and dried air is delivered to the building. The air now has a lower dew point called the exit dew point."

    Call a Heating and Cooling business and ask them what the "magic" number for Dew Point is for your area. I have "Weather Bug" on my computer, so I can quickly see what my dew point temperature is right now - 67°, which is uncomfortable when the temperature is 86°F and the humidity is currantly 51% = 89°F heat index. Our heat index was 103°F the other day, so we are HOT and Humid. Our high yesterday was 99°F.

    We just had our A/C unit serviced and the technician said we couldn't do anything better than what we were already doing by controling humidity with a dehumidifier and leaving the A/C on, now that we have extremely high dew points every morning, that last well into the afternoon.

    I had the Watt A Meter on the dehumidifier for 12-hours. The cost: 18-cents/day, $1.27/week, $5.46/month.

    We keep the "envelope" of our home closed - we enter and exit our house through our laundry room (just off the garage) as much as possible. We enter the laundry room through the kitchen. SHUT THE DOOR. Then open the door to the garage. This helps maintain the temperature/humidity.

    As the technician explained. If you open your front or back door, which are directly into the home, you lose your cooling sealed inside your home (the "envelope"), and your A/C has to start all over again due to heat and humidity added by opening the door. By using the "air lock" in the laundry room, the change in temperature and humidity are confined to that one closed-off room.

    So if you have a family that runs in and out, consider how you can create an "air lock" in your home, which will help your air conditioner not have to work so hard.

  3. #3
    Registered User sabrelvssammy's Avatar
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    wow...i can't really add anything to grainlady's post...that's some awesome information that i am going to re-read when i can concentrate a little better....

    however, for us, we run a de-humidifier in the main part of the house and i truly believe that is is affecting the temp & air quality around us. We are emptying 45 pints of water every couple of hours. To me, it makes the rooms feel cooler (maybe just a feeling) but if i 'feel' cool then i don't run the ac as much. I have also shut all the doors to rooms that we don't use so that we are just cooling and controlling the parts of the house we truly live in. With the de-humidifier going and the shades pulled before the morning sun can start beating into the house i am able to keep from running the ac until late evening..(i am still from the school that it costs more to run it all day long than to keep it off and have it cool a hot house down at one time) i'm sure others will disagree coz this has been a long standing hot debate for as long as i can remember.

    I think the kw used to run the de-humidifer will far outweigh the costs of running the ac as much.... just my two cents worth....

    “After the last tree has been cut down, after the last river has been poisoned, after the last fish has been caught.
    Only then will you find that money can't be eaten.”

    ~ Cree Indian Prophecy










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    Registered User warramra's Avatar
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    Thank you! I will have to start shopping as I think it might be worth it. If I could just use it so the AC doesn't have to run as much (we keep it set at 82) and work as hard when it runs it would help. Our house is shaded and we don't have as much influence by solar heating as we do humidity. We don't mind it warm, but swimming through the air is not fun.
    Amy

    Wife to one hardworking man
    Homeschooling mom
    Three girls 14,11 & 9
    one boy 7

  5. #5
    Registered User sabrelvssammy's Avatar
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    Quote Originally Posted by warramra View Post
    Thank you! I will have to start shopping as I think it might be worth it. If I could just use it so the AC doesn't have to run as much (we keep it set at 82) and work as hard when it runs it would help. Our house is shaded and we don't have as much influence by solar heating as we do humidity. We don't mind it warm, but swimming through the air is not fun.
    don't forget to save all that 'free' water to water your plants, pour in the back of the toilet tank, etc....

    “After the last tree has been cut down, after the last river has been poisoned, after the last fish has been caught.
    Only then will you find that money can't be eaten.”

    ~ Cree Indian Prophecy










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    Quote Originally Posted by warramra View Post
    Thank you! I will have to start shopping as I think it might be worth it. If I could just use it so the AC doesn't have to run as much (we keep it set at 82) and work as hard when it runs it would help. Our house is shaded and we don't have as much influence by solar heating as we do humidity. We don't mind it warm, but swimming through the air is not fun.
    I just wanted to add that I wouldn't buy an older model dehumidifier. I would make sure to buy an energy efficient one because mine is lot older and it uses way more electricity than grain ladies does.

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    Registered User ahmom's Avatar
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    My dehumidifier makes quite a bit of heat. It's 3 years old. I wouldn't use it to try to cool the place down.

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    Quote Originally Posted by ahmom View Post
    My dehumidifier makes quite a bit of heat. It's 3 years old. I wouldn't use it to try to cool the place down.
    Humidifiers don't cool, they remove excess moisture from the air so your air conditioner can work more efficiently.

    Having a dehumidifier in the basement is a MUST around here to insure dry storage and cut down on potentially dangerous mold growth. If you maintain humid indoor air above 50% humidity, you can also expect more dust mites in your home, which can be dangerous for some people with asthma or other breathing conditions.

    If you turn your air conditioner off during the night and your home air is saturated with moisture the next morning, using a dehumidifier during the more humid morning hours to remove humidity from the house will help the air conditioner the rest of the day, when you turn it back on. Better yet, just keep the air conditioner on all the time when dew points are high overnight.

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    Registered User tervsforme's Avatar
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    I have a humidifier in my basement and really noticed a difference after just a day of having it on. It ran continuously for about a week or so and now, based on the setting, it shuts off automatically for a while in the evening. I definitely think they are helpful.

  10. #10
    Registered User lisaflex's Avatar
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    they are helpful. do get a large energy effecient one though. mine runs in the basement from late april - sept.

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