Why Humidity Control Is Important in the Cooling Season

Learn why humidity control is important during the cooling season.

When it comes to cooling your home in some regions of the country, humidity is as big of a problem as high temperatures.  Unlike the arid Southwest, the Southeast and parts of the Midwest have very high humidity in the summer months and this can result in higher than necessary energy bills if you aren’t careful.

Humidity is behind the “heat index” you hear on the weather report and drives the “feels like” temperatures that are usually several degrees hotter than the actual temperature.  Selecting and properly sizing your air conditioning equipment to deal with humidity is a little more difficult than just getting something that keeps you cool on the hottest days.

The Basics of Removing Humidity

Most central air conditioning systems are capable of removing humidity from the air in your home. Window units or ductless systems do not generally move enough air through the system to remove the humidity evenly from your entire home or workspace.  While most central AC systems will work, effectively controlling your humidity so you’re comfortable day and night is best achieved with a high efficiency system.  Why?

  • To remove humidity, an air conditioner has to be running.  Basic, minimum 13 SEER systems typically run in either “on” or “off” mode.  High efficiency systems (16 SEER and up) usually provide variable speed capacity which can run longer on lower power, giving the system more time to remove humidity.
  • High efficiency systems are able to control the temperature more precisely, eliminating noticeable cold or hot swings and not allowing humidity to build up in the air.
  • Because the air is constantly being conditioned with a high efficiency system, there is much less chance of stagnant humid air causing mold in the walls or attic.

Additional Benefits

In addition to the added comfort you’ll feel with a high efficiency system capable of removing humidity, they also run much more quietly, which can be a benefit at night when you’re trying to sleep.  Because they run on variable speed, high efficiency systems are also much more energy efficient, which translates to money saved every month on the energy bill.

The Bottom Line

If you live in an area of the country that is naturally humid, talk to your contractor about humidity control and higher efficiency systems that can provide you with a comfortable environment, not just cold air.

After reading this are you more or less likely to explore a high efficiency system?  How important is humidity control in your home?

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18 thoughts on “Why Humidity Control Is Important in the Cooling Season

  1. Thanks for sharing this blog. Your blog provided us with valuable information. keep on posting! see here : http://www.cellocoolers.com/desert-coolers/

  2. Frank I would like to offer some thought on humidity, I am from the Dallas area, I am in the restoration business, I agree a AC solution is a valid solution in many cases, but an AC unit cannot cover all the bases, we know that the RH in some parts of the country is 70% or better 200 days a year, and as the best of units generally will remove 30 to 50 % during a single air change this does not account for the Stack effect, some homes have a stronger effect than others. so when the energy envelope is open either at top with attics or top and bottom as with a crawlspace this changes everything, Just saying, look at the entire home system not just the AC, I do believe this open forum is a great way to inform people, and you do a great job at it. thank you T.

  3. I live in CA High Desert
    Have swamp cooler in 1580sq ft mobile home
    Temperature is 56 and 88% humidity!
    Driving up my chronic back pain so I can not function and
    Can barely move
    How can I bring down humidity?!
    Moved from No CA, always had central heat and air units don’t recall this type of pain
    How can I lower indoor humidity
    To lower my pain?
    Thanks

  4. This is a helpful article. I live in Minnesota and we leave for two cold winter months. I am looking for a humidity sensor to connect to my bathroom fan. And I want that fan to turn on when the humidity is high(above 30% at 10degrees Fahrenheit. My goal is to not run the bathroom fan continuously for two months, but have it come on and go off as necessary. Can you suggest a product for me? I am looking for a switch to replace the manual bathroom fan switch and need a sensor that is sensitive enough to measure humidity levels at low levels. We need to prevent condensation on living room windows and invisible condensation within walls. Thanks.

    • Hi Robert – This is an interesting question. I did a quick internet search using the terms, “humidity sensor switch” and found a lot of options which might work for you and some were available at retail hardware stores. Another thought might be to (also) consider using a portable dehumidifier and have it set up to pour the condensate into a drain instead of into an accumulation container. I know this might be a problem at very low temperatures with frozen drain lines but maybe the humidity levels would not be too high when it is that cold or could add a small auxiliary heater by the dehumidifier. I hope these suggestions help you with your HVAC project!

  5. Hi Tom,

    A properly sized, central air conditioning system is designed to effectively address both latent (humidity) and sensible (temperature) heat loads. Heat energy that causes a change in the temperature of a substance is called sensible heat. Sensible heat is the heat load you can actually feel, and is driven by the difference in actual temperature or where you set your thermostat. Latent loads are related to humidity removal performed during the cooling process to achieve the sensible (temperature) load. When you open up windows on a humid day you will probably be introducing humid air to your home that will eventually have to be removed (when you close the windows and turn on the AC). So, yes, both humidity reduction and temperature reduction can drive energy costs, though it is difficult to say how much energy is spent on each without the ambient conditions.

    People living in hot, humid areas usually define “comfort” as having the right combination of both lower temperature and lower humidity. The actual amount of energy spent on each will depend on the outdoor ambient conditions and where you set your thermostat. However, there are other factors besides temperature and humidity which could also be considered as part of a person’s comfort. For example, introducing controlled fresh air into a conditioned space might also provide some comfort benefits and we hope to report on some of these new concepts in future articles on this site. (check back)

    Hope this helps,
    Scott

  6. My wife insists on opening the windows in Florida when the temp is 75 and the humidity is 98%. I tell her this is not good she insists that the humidity will come down during the day. I say it just makes the air conditioner work harder to bring the humidity down, she say’s no. I say leave the windows closed until the temp and humidity come down. She is from Michigan and has done this all her life, I tell her she is not in Michigan now!

  7. My garage florescent fixture/bulbs seem to not work after a storm, where the humidity is high. I live in the Fort Myers area, and have lived in this house for over 10 years. This has just become a problem recently. After a few storm free days, the light will again function properly.
    Need advice on how to get the fixture working properly

  8. I reside in Houston. I set my house at 73 to 75 degrees I am finding the humidity level at 80%! Inside i have found mold on the furniture and walls. I purchased a dehumidifier (portable) and it is helping. How can I fix this issue. This is a new build house.

    • Hi Orlando – In most cases, if your system is keeping your space cool but the humidity is still high then for some reason, the system is not running long enough to remove the moisture from all the air in the space you are cooling. Basically, it runs long enough to cool the space near the thermostat but it shuts off too quickly when it hits the set point. That means that a lot of the air in your space does not have enough time to pass over the cold coil inside your unit which should be condensing the moisture onto the coil, removing it and leaving dry, cool air coming out of your system. This moisture should be collecting in a drip pan and which is then passed out to a drain tube and removed from your space.

      There are several common reasons for this which I will describe. One is your system might be sized too big (too much capacity in BTU/Hr) for the space you are trying to cool or something has changed in your space that makes it operate like it has too much capacity. For example, if you have closed off large areas of your home to reduce the energy used on air conditioning then the system might be trying to cool a much smaller, remaining space than it was designed for. Some high efficiency, variable capacity systems allow you to significantly reduce the load without this issue but if you have a fixed capacity system in a highly humid area you could see this problem.

      The problem of having too much capacity can also happen with ductless mini-splits if they have too much capacity for a given “zone” or “room” you are trying to cool with them. In this case, you might try increasing the airflow between the various zones you have set up with fans to make sure the load is balanced between the spaces. For example if all the units are set to a very low temperature and the combined capacity of all the units, running at the same time, is too much for your space you could be having problems with the total run time for all the units running together and have the same problems with humidity that were described above.

      In the short term, you might try some tactics to get the run time longer on your system(s) like setting the thermostat temperature lower and increasing the airflow to all parts of your home with fans. You might try letting more sunlight in or doing something to increase the required load and again, get the run times longer. If these tactics do not work you might want to have an HVAC contractor come out to do some load calculations (ACCA Manual J) to see if your capacity is right for the space you are trying to cool. Here is a link to another article on this site that deals with humidity.

      http://www.ac-heatingconnect.com/understanding-temperature-humidity-modulating-hvac-system-might-right/

      I hope these suggestions help with your problem.

  9. I reside in Fl. my indoor a/c is set at 76 to 78 and my device shows humidity at 41 or lower. What is too low and too high in humidity as I have allergy.
    Thanks

    • Hi Eileen,

      Comfort level based back against humidity varies with temperature for both the heating and cooling season. I found this article which does a great job at explaining it.

      http://highperformancehvac.com/comfort-health-humidity-levels-factors/

  10. the humidity in my condo goes up when ac system runs. I do leave fan on constant and ac comes on and off as required. as I write the temp inside is 72 and the humidity is 69. the ac is in the attic and the condensation pan is dry.any ideas?

    • Sounds like your system might be either oversized (too much cooling capacity for your space) or the fan speed might be set too high. The unit is probably cooling properly to satisfying temperature control but it is not running long enough to take the humidity out of the air. If you have some rooms shut off and are cooling a much smaller space than the size assumed when the system was selected this might also cause the short run time problems. Also, if the outdoor temperature is not high but humidity is high (like right after it rains) you might try taking the thermostat temperature down a few degrees at a time until you get a little longer run time to see if that helps. If none of those things work have a qualified HVAC contractor check to see if the capacity and fan speed are right. Might have them check the charge level too and perform some cleaning and maintenance while they are there.

  11. For application assistance in Saudi Arabia, please email your contact info to Rani.Venugopal@emerson.com and they will try to help you. thanks.

  12. Dear sir
    we are in one of the leading (abrsive) cutting and grinding wheel manufacture in Saudi Arabia ,
    our product most be need the a/c ,as per our STD tem is below meson Min 20C , Max 22C ,Humidity 60% to 70%
    but actual tem is min 20 C to max is 23 C come but humidity is actual is 30% to 40% only come

    actual our production area side is 510 mtr that room we will use the 25 ton package type centennials A/C ,
    we are try to may way but we can not reach the humidity , how to maintained the a/c Indoor Relative Humidity between 40% and 60%

  13. You are on the right track to have an AC contractor inspect the system to determine why it is not removing humidity. If you are not satisfied with the answers you get from the building contractor and his HVAC expert you might want to get another opinion from a different contractor. Your AC system should be removing humidity from your home as well as cooling it. I hope this helps.

  14. i had a brand new, small (1070sf) home. 2×6 exterior walls and some kind of spray foam for the attic – very expensive. i do not want to pay high utility bills and went to the extra trouble to ensure this. i moved into the house then started noticing things like, the salt was one clump, floors were not drying after mopping, condensation on the windows in the am, dish and hand towels weren’t drying out between uses and finally after being gone a couple of hours one day, i came in the house and it felt like a sauna. bought a humidity detector and it was pegged at 85%. i am terrified. i spent every penny i own on a new house that has a serious problem. my contractor is coming over today and it won’t be a friendly visit. he did send his a/c guy over to open the damper in the attic and that did no good.

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