why is my house so humid with the AC on

Why is My House so Humid with the AC On?

Why is my house so humid with the AC on? If the air conditioner is not reducing at least a little bit of humidity in the home, then you know there is an issue somewhere. And finding out what that issue is is hopefully not too difficult. Following is a few of the most common issues when the humidity is overtaking the AC.

AC is cooling but not removing humidity 

One of the most common reasons that the air continues to feel humid when the AC is running is that the thermostat is s set on “on’ instead of “auto”.

1.AC fan mode 

When the AC fan mode on the thermostat is on the “on” position, it continues to run after the compressor has shut down.

What does that have to do with the house feeling humid?

Because as a air conditioner is cooling the air it is also gathering the humidity from the air in the form of condensation on the refrigerant coils.

And then  when the air conditioner cycles off, the moisture gathered on the condenser coils drains into a drip pan and either continues through a drain line outside or is pumped outside with a condensate pump.

But when the AC fan mode is set on the “on”  position, the condensation that has gathered on the refrigerant coils doesn’t get a opportunity to drip off. Instead it is blown by the fan which is causing it to evaporate back into the ductwork.

Which means that even though it is gathering the moisture out of your air as the air conditioner is running, it is circulating it back around your house while the AC compressor has cycled off.

Try turning the AC to “auto mode” and seeing if the air starts to feel less humid.

Humidity goes up when the AC is on

2.  Foam insulation

Another reason build a home can feel extra humid with the AC on is the type of insulation that is used in the Attic.

Foam insulation is notorious what causing the Attic to be extra humid.

Heat and moisture from the attic can
make its way into your duct system a few different ways.

3. Leaky ducts

If your ductwork has got any leaks, it can be pulling hot humid air from the attic into your ductwork and then into your home.

4.  Kitchen fans

If the powered vents above your range are extra strong, they could be pulling air from the attic.

AC is cooling but not removing humidity When the Attic is the source of the humidity that is circulating in your home , there’s a couple of things you can do to alleviate the problem.

1.  Have your attic inspected make sure that it is sealed properly.
2.  Have you heard ductwork checked for leaks.
3. Run a dehumidifier in the Attic.
4. Reroute the ductwork so that the Attic is air conditioned along with the rest of the house.

House feels damp with AC on

A.Heat rises

Sometimes you might find that the reason your house is feeling humid is the layout of the house itself.

If you have a two or three story house and the top floors feel extra humid compared to the bottom floor then your air handler is not equipped to handle the downstairs and upstairs equally.

You may find that you need to run a dehumidifier upstairs to help your air conditioner run easier and do a much better job at controlling the climate inside your house.

B. Room is muggy

Many times it’s not the whole house that feels muggy with the AC on. It could be relegated to just one or two rooms.

The most obvious solution is that the ductwork that specific room is leaking and mixing the humidity from the attic for crawl space with the air coming into the room.

5.Ductwork design

If the ductwork is not zoned correctly or if additional vents have been added to the zones, the rooms were they additional vents have been added may not get the same level of dehumidification that the AC provides to the rest of the house.

Some rooms like basements do not even have AC ducts ran to them. Proximity to the moist ground is usually the culprit for high humidity in the basement.

Running a dehumidifier is a great way to dry out the basement and make it useful and livable.


Does your house feel extra humid when the AC is on?

And air conditioner is made to dehumidify the air as it is cooling. One of the primary ways it cools the air is by reducing the moisture in the air.

So when your ear feels extra humid with the AC on, it is definitely not a natural cause.

What are the main reasons a house will feel muggy when the air conditioner is on is that the humidity that the AC is supposed to be reducing is being redistributed throughout the house.

This can happen when the AC fan mode is switch to the on position so that the fan is running continuously when the AC compressor has cycled off.

” AC auto mode” is  the setting on the thermostat to use to ensure that the humidity gathered on the condenser coils drains rather than being evaporated and redistributed around the house.

Another culprit for humidity getting into the house with the AC on is leaky ducts. If your ductwork has leaks in it, then the humid air inside of the attic can leak inside of your home through your ductwork.

Another reason that the home feels muggy with the AC on could be the layout of the house. If for instance, the house is a two-story house, the top level may feel extra humid simply because heat rises.

A easy fix that will not only reduce the humidity on the second floor as well as aid the air conditioner is a dehumidifier.

Do it yourself AC Coil Cleaner

Published by

Dennis Reed

Dennis Reed Owner and Author @ BreatheBetterAir.org