High Humidity in new apartments

Title: High Humidity in new apartments.

The past two months I have been trying to mitigate humidity in my apartment. My humidistat (a device that monitors relative humidity indoors) was reading around 75-80 % humidity.  At 80% humidity walls can start condensing and having water droplets form. Luckily this was not the case with my place. (I was using an overhead fan, and running the fan that circulates the air from the thermostat.

My blankets were damp feeling, my clothes in my closet were slightly damp, and the couch was damp. I knew something needed to change. I am currently located in the Midwest and I am writing this in the Summer. I realize humidity will go down in cooler months but I knew something was wrong.

Fast forward to about a month living in the apartment I decide it was time to buy a dehumidifier. I do not want to have dampness around the whole home potentially causing health and moisture issues.

I got a 22 pint dehumidifier from Walmart. It started to work wonders on the apartment first in my room, (box instructions mentions to run the unit for 24 hours when first getting the unit. I got my room down to 50% humidity within the first few hours and emptied the bucket. I decided to bring it to the main room to try to help mitigate that area as well. (since all rooms were reading the same humidity with the air circulation in the unit.) I was amazed how much water was in the air. Fast forward 24 hours and I continued to pour out multiple full buckets from the dehumidifier.

I bought the unit on July 22 and It is currently August 9th. We empty the dehumidifier multiple times a day. If you are gone for a couple of hours you come back and it has turned off because it is full.

Okay... something is wrong here. I started looking up how much electricity we will use if we are running this 24/7 365. It would be spendy. ((Attach data))

(kWh in my current city)

Rough Estimate of how much running dehumidifer 24/7 would cost. (I am not sure if I did this

correctly but for the sake of the argument, I belive it was going to increase the energy bill.

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With that being said I was not expecting to run the dehumidifier for the whole year.

It is now January 2026 as I am finishing this article and the Dehumifier has been packed away since the fall.

At $74.30 per month I was looking for different alternatives or where all this humidity was coming from.

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I have been positioning the dehumidifier in different places to try to mitigate the issue, I set it up facing the large sliding door thinking that there must be tons of leakage and all the humidity is entering the cracks and holes. The supply grill that brings air to our rooms is close by and I was trying to make a barrier between those so by the time the air got to the supply grill it would be dry and better for our rooms. I have realized this was not working although their may be slight leakage or humidity coming from the large sliding door, this was not the issue. With the dehumidifier off for 1-2 hours the humidity will spike up 10-20%.

I have suspected our heating and cooling unit is oversized for the amount of space we have. This can cause problems because if the unit is oversized it is designed to work at its maximum performance at  temperatures you would not normally experience or temperatures that we do not experience most times during the year. An oversized unit will only address the hottest Ex: 10-50 hours and work efficiently for those hours. The unit will not work correctly or efficiently for the hundreds if not thousands of other hours.

A properly sized unit will work best during the mean/most hours of the year.

Quick recap. If your unit is oversized you are only going to get adequate cooling and heating with proper dehumidification for lets say 100-105 degree times not days. It might equal out to 150-200 hours of adequate dehumidifying hours. It could be more like 100-150 hours of the year (4-6.25 days of the year) depending on how oversized your equipment is.

Compared to a properly sized unit that will be adequately addressing temperature as well as humidity for something like 300-350 days of the year.

Why do some houses get oversized units?

This is a complex and tricky question. Some houses get oversized units because their house has leaks/tightness issues. They loose conditioned air from leaks or lack of insulation in the home. Thus requiring a bigger unit to keep up with the desired temperature. If these leaks were addressed or fixed you would be changing the house whether you like it or not. Fixing leaks could make your system more in tune with your house it could also make your unit even more over sized than it was before. The temperatures, air sealing/tightness and the heating and cooling unit all work together. You can find this information and data out to have your systems work properly and in harmony by testing your home for air leakage as well as a manual J calculation.

Your unit only runs for short intervals it is not only hard on the equipment but it is not doing what its designed to do.

Air conditioning units need to run for 10-15 minutes before they start to take the humidity out of the air with the evaporator coil. BINGO!

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Yesterday night I was sitting on my couch texting friends when I heard the AC kick on. I clicked through my phone and turned on my Stopwatch. It surprisingly went for 9mins 50 seconds. I timed the unit once more and got almost exact same time maybe closer to 10 mins.

My hypothesis: I have two machines that are acting like dehumidifiers. Remember when I said that a cooling unit needs 10-15 minutes to START drying the evaporator coil. Here is what I believe to be happening. The AC kicks on for 10 minutes, It then cools the house and also pulls in air. After those 10 mins are up the coil is wet the apartment is the correct temperature and it turns off. Then from their the circulating fan that brings the cold wet air into our rooms and our apartment is distributed with humid air. Our apartment will be 73 degrees with 80% humidity if we do not change anything. Also if you wonder why don't just turn off the circulating fan it is because the CO2 levels get to a unhealthy level in our rooms without it.

Yesterday night I decided to make a change I went to the thermostat and turned off the unit. When I got up I was comfortable and I walked out thinking it was still 73 degrees. It was 78 degrees and the humidity was quite low for us 60%. I turned the unit on let it run from 78 all the way down to 74 or 73 and then turn off the unit. This allows the unit proper time to dry the evaporated coil at least slightly and lets the unit run for twice as long if not longer.

What to do when we are gone?

Currently the temperature is back to 77 degrees and the humidity is staying around 50%. This is much preferred to the other situation.

With that being said I do not know what Fall or Winter will be like in this situation. I hope you found this informative and interesting.

If you would like to discuss more email me at cartereidem@gmail.com

Writing this end of the blog on January 2026, a solution was found.

The main room for improvement to reduce humidity included the AC unit running for 10 minutes.

What I did to mitigate this issue was to:

What Worked (apartment living)	What didn't (apartment living)
Only using thermostat when temperatures increased by multiple degrees (run time increases!) turning it off once reached tempature	Set it and forget it (leaving thermostat at certain degree
Results	Results
Humidifier ran less often:humidity decrease	Running Humidifier 24/7 humidity stays regardless of whole house fan or circulating
Home was warm when getting home but much drier	Home was cool and wet (resulting in damage lung term)