[ithos]

In many commercial buildings, they have electric or hot water reheat in the ducts so that if the amount of HVAC cooling needed to dehumidify lowers the room temperature below setpoint, the air is heated back up before it enters the space.

Ideally the home would have a variable speed compressor and fan. Lower energy costs with humidity and temperature much more stable. Also won't have that blast of hot air in the summer when your AC fan kicks on.

Variable Speed HVAC Technology | Heating and Cooling Benefits

[C. C. Rider]

There are several issues at play here. First, having the FAN running is not the same thing as having the AC running. Depending on temperature, your fan could run all the time, but the AC would never do any dehumidification.

Second, as some have said, the AC (or the heat) must be on in order to dehumidify. By "on", I mean RUNNING, not just set to the "ON" position. The AC is "on" when it's compressor is running, not just when the fan is on.

Here is what confuses a lot of people. How much the AC actually RUNS depends on what the outside temperature is. If it's 90* outside, then your AC will run enough to dehumidify your house nicely. If the outside temperature is in the 60's or 70's, then your AC WON'T run enough to do much dehumidifying.

If the outside temperature happens to be in the 60's or 70's and it's raining or humid outside as we had several days ago, then your AC is NOT going to do much, if any, dehumidification because it won't be running. In that case, you will need to purchase 1 or 2 individual dehumidifiers for your home if your thermostat doesn't have a "Dehumidify" setting.

A "Dehumidify" setting on your AC simply means that when it kicks on, it runs the AC on low speed even though the inside temperature demand on the thermostat has been met. This may make it cooler in your home than you want, but that's the price you'll pay for using the "dehumidify" setting.

High humidity is not usually a problem in most homes in this area when it's hot (83* and above) or when it's cold (30's and 40's). The problem occurs when the temperature is mild (60's and 70's) and the weather outside is rainy and damp. THAT's when you'll have a humidity problem in the house and need either a dehumidify setting on your thermostat or a separate dehumidifier unit (or two).

Actually, having separate dehumidifier units will work best under extreme conditions, but most of the time, having a dehumidify setting on the thermostat will be sufficient. Hope this helps your understanding of the problem.

[ithos]

Originally Posted by Notsocrates

The "humidity" is really relative humidity: the amount of moisture in the air compared with the total amount it could hold at that temperature. The capacity of air to hold moisture increases as the temperature goes up and decreases as it is cooled.
So, if you start with air at 95 degrees with relative humidity of 70% and cool that same air to 75 degrees the relative humidity will increase.

This is a very important point. Heating a room may lower relative humidity but it will not "dehumidify" as no moisture is being removed. It is astounding how many HVAC techs do not understand that.

Controlling RH is also important in areas where condensation can cause damage.

[Nofiner]

CTry going to the A/C temperature control and see if there is a Humidity setting and if so set it about 50 to 55. The A/C unit will run and should indicate Dehumidify on the control. You might feel some heat but that is normal as the A/C works.
Good Luck

[Indydealmaker]

Originally Posted by Grumpy218

I recently purchased a home in the villages. The house was built in late 2017, so it's fairly new. I've noticed that it feels very humid in the house. The thermostat is set on 74 degrees and it maintains that temperature but it registers a humidity of 63%. The humidity would be great if I wanted to turn my home into a humidor!!! I don't think my wife would go along with that idea.

I moved here from Poinciana, FL so I'm familiar with the Florida humidity. My home A/C in Poinciana was set at 75 degrees and it was cool to the point we used blankets in the evening to watch TV.

Is there something I'm missing, e.g. have the freon checked in the A/C unit? Flush out the condensate line (although there doesn't seem to be much condensate exiting the house). Or could it be something else. Is a whole house de-humidifier the answer?

All feedback is welcome!

We experienced the same thing. Our Hvac guy attributed the problem to the fact that we kept the fan running full time which sucked in humidity when the AC was not running.

[C. C. Rider]

So, if you start with air at 95 degrees with relative humidity of 70% and cool that same air to 75 degrees the relative humidity will increase.

That's not true if you use an air conditioner to cool the air because the air "conditioning" process removes moisture as it cools. That's what the condensate drain line is for... to carry away the moisture that has been condensed out of the air. This leaves you with cooler, drier air for your living space.

Now if you were living in a cave and had a giant fan to pull hot air into your cave where it was much cooler, then the humidity of your cave would be higher than the outside air, but that's not what happens with air conditioning in our homes because air conditioners REMOVE moisture. That's why they're called air CONDITIONERS and not air COOLERS... because they "condition" the air, i.e. remove moisture AND cool the air.

[barbyboc]

We just had the same problem fixed by Priorty Air Conditioning. It was the fan motor. Immediate reduction in humidity.

[silver.bullet]

Grump, Take a look at the April Air whole house dehumidifier. We had one installed 3 years ago at $3.5k , 2400 sq foot electric a/c, gas heat, I use it about 5 months it samples air every hour and turns on the dehumidifier if necessary. The other months the a/c or heat dries the air. I love it, keeps air at 55% and so comfortable. Good Luck my friend!

[retiredguy123]

Originally Posted by silver.bullet

Grump, Take a look at the April Air whole house dehumidifier. We had one installed 3 years ago at $3.5k , 2400 sq foot electric a/c, gas heat, I use it about 5 months it samples air every hour and turns on the dehumidifier if necessary. The other months the a/c or heat dries the air. I love it, keeps air at 55% and so comfortable. Good Luck my friend!

I don't understand why you would need a dehumidifier to maintain a relative humidity of 55 percent in your house. I keep the heat pump thermostat set at 78 degrees all year, and the humidity never even comes to 55 percent. The humidity level in my house is almost always between 40 and 50 percent, with only heating and cooling, and no dehumidification at all.

[Topspinmo]

I am really confused now? Would some explain what the control that controls humidity supposed to set on. Some say 50% some say 60% and some say to the on position. So what is it? IMO has nothing to do with A/c cause it’s set to desired temperature on automatic.

[retiredguy123]

Originally Posted by Topspinmo

I am really confused now? Would some explain what the control that controls humidity supposed to set on. Some say 50% some say 60% and some say to the on position. So what is it? IMO has nothing to do with A/c cause it’s set to desired temperature on automatic.

The typical builder installation does not include a dehumidifier. But, the standard heat pump thermostat includes an optional "humidity" setting that will allow the AC to cool down the house to about 3 degrees below the thermostat temperature setting to remove moisture when the humidity goes above the humidity setting. This is a "compromise" because you need to cool down the house to below the desired temperature to reduce the humidity. Personally, I don't use the humidity setting because it makes the house too cold when the humidity setting kicks in. But, for snowbirds, the humidity setting can save electricity by allowing a higher temperature setting when the house is unoccupied. A "real" dehumidifier will overcool the house to reduce humidity, and then reheat the air to the desired temperature, so you can control both the temperature and the humidity as desired. The standard builder system does not include a real dehumidifier, so you cannot control both the temperature and the humidity. I hope this makes sense.

[Topspinmo]

Originally Posted by retiredguy123

The typical builder installation does not include a dehumidifier. But, the standard heat pump thermostat includes an optional "humidity" setting that will allow the AC to cool down the house to about 3 degrees below the thermostat temperature setting to remove moisture when the humidity goes above the humidity setting. This is a "compromise" because you need to cool down the house to below the desired temperature to reduce the humidity. Personally, I don't use the humidity setting because it makes the house too cold when the humidity setting kicks in. But, for snowbirds, the humidity setting can save electricity by allowing a higher temperature setting when the house is unoccupied. A "real" dehumidifier will overcool the house to reduce humidity, and then reheat the air to the desired temperature, so you can control both the temperature and the humidity as desired. The standard builder system does not include a real dehumidifier, so you cannot control both the temperature and the humidity. I hope this makes sense.

Yes, I am guessing older houses don’t have heat pumps? My don’t gas furnace.

[retiredguy123]

Originally Posted by Topspinmo

Yes, I am guessing older houses don’t have heat pumps? My don’t gas furnace.

Actually, a lot of the older houses do have heat pumps, but some houses, newer and old, have gas heat.

[silver.bullet]

Originally Posted by retiredguy123

I don't understand why you would need a dehumidifier to maintain a relative humidity of 55 percent in your house. I keep the heat pump thermostat set at 78 degrees all year, and the humidity never even comes to 55 percent. The humidity level in my house is almost always between 40 and 50 percent, with only heating and cooling, and no dehumidification at all.

When the A/C and heat run, the dehumidifier is not needed, the humidity in the house is low. In the spring and fall is when I use the dehumidifier. Works like a charm!