By Jake Lawson
When I hear from homeowners that their home is “cold but still sticky,” I know where the conversation is headed. They are often surprised to find that temperature and humidity are two completely different things.
Many assume that air conditioning lowers both the room temperature and the humidity at the same time. In fact, cooling the air is half the comfort equation. Too much moisture inside can make your room still feel clammy, uncomfortable and even warmer than the thermostat says. I've seen this many times when looking at older through-wall air conditioners. The equipment still blew cool air, but because it didn’t control the humidity very well anymore, or maybe it never did that well in the first place, the overall comfort level just wasn’t there anymore.
Modern heat pump through-the-wall systems are designed for more than just cooling capacity. Better air flow management, improved coil design, more precise controls and advances in refrigeration technology all contribute to more effective moisture removal during normal operation. While every home and climate is different, many homeowners find newer systems provide a more balanced indoor environment rather than just blowing colder air.
In this article, I’ll explain why humidity matters, why older air conditioners often struggle with it, and why today’s heat pump through-the-wall systems often deliver noticeably better comfort throughout the cooling season.
💧 Why Humidity Matters Just As Much As Temperature
One of the biggest misconceptions I hear is that indoor comfort is determined entirely by the thermostat.
It isn't.
Imagine two rooms that are both kept at 72°F (22°C). One room is about 45% relative humidity, the other about 70%. The temperature is the same, but almost everyone will say the second room feels warmer, heavier and less comfortable. That’s because the amount of moisture in the air impacts on how well our bodies are able to cool themselves. We naturally give off heat by evaporation of perspiration. When the humidity is high, that evaporation slows down and we feel warmer even though the air temperature is the same.
Indoor humidity affects a variety of other things within the home. Excess moisture can lead to condensation on windows, musty odours, mould growth, dust mites and an overall feeling of stale indoor air. Conversely, if the air is too dry, it can cause itchy skin, dry eyes and general discomfort during the winter months. According to the U.S. Environmental Protection Agency (EPA), maintaining indoor relative humidity between approximately 30% and 50% helps improve indoor comfort while reducing conditions that support mold growth and other indoor air quality concerns.
You can learn more from these trusted resources:
- 🌎 U.S. Environmental Protection Agency – Indoor Air Quality: https://www.epa.gov/indoor-air-quality-iaq
- 🌎 U.S. Department of Energy – Energy Saver: https://www.energy.gov/energysaver
- 🌎 ASHRAE: https://www.ashrae.org
📊 Comfortable Air vs Humid Air
| Balanced Humidity ✅ | Excess Humidity ⚠️ |
|---|---|
| Comfortable indoor feel | Sticky, clammy rooms |
| Better sleep | Restless nights |
| Less mold potential | Higher moisture risk |
| Improved indoor air quality | Musty odors |
| Better overall comfort | Room feels warmer than thermostat |
One thing I've learned over the years is that homeowners rarely complain by saying, "My humidity is too high." Instead, they'll say things like:
- "The house just feels damp."
- "Everything feels sticky."
- "The AC never seems to get comfortable."
- "The room cools down, but it never feels fresh."
Those comments usually point toward humidity rather than temperature alone.
🌬️ How Air Conditioners Actually Remove Humidity
People often assume that an air conditioner somehow "dries" the air using a separate system.
It doesn't.
The cooling process itself removes humidity as a natural by-product.As the warm indoor air passes across the evaporator coil inside the unit, the refrigerant absorbs heat from the air. The coil is much cooler than the air around it, and moisture starts to condense on the coil, just as water droplets condense on the outside of a cold glass on a hot summer day.
The condensate is collected inside the unit and safely drained to the outside via the condensate drainage system. The cooled and drier air is sent back into the room at the same time. In other words, every properly working air conditioner removes both heat and moisture at the same time.
The amount of humidity removed depends on several factors, including:
- 💧 Indoor humidity level
- 🌡️ Outdoor temperature
- 🌀 Airflow across the evaporator coil
- ❄️ Coil temperature
- ⚙️ Equipment design
- 🏠 Room conditions
This is one reason proper installation is so important. Airflow, drainage, and equipment sizing all influence how effectively moisture is removed.
❄️ Why Many Older Through-the-Wall Air Conditioners Struggle
One question homeowners frequently ask me is:
"If air conditioners have always removed moisture, why do newer systems seem to feel so much more comfortable?"
The answer isn't that older equipment couldn't remove moisture. Many older systems just weren't as good, or consistent, in doing it.After a few years of service a number of things start to take their toll.If filters are not cleaned regularly, dust collects on evaporator coils. Airflow is increasingly restricted. Fan motors are less efficient. Failure to perform maintenance can result in diminished refrigerant performance. Older control systems often offer less precise temperature control, leading to equipment cycling differently than newer units.
Even when everything is working properly, HVAC engineering has made great strides in the last decade. Manufacturers have improved coil design, blower performance, electronic controls, refrigerant technology and overall system efficiency.
The result is often better equipment which balances cooling and moisture removal better than simply lowering air temperature. I have changed out many of the older through the wall units that homeowners immediately commented the room "felt fresher" within days after installation. The thermostat setting hadn’t varied much—but the indoor atmosphere had.
📊 Older Units vs Modern Heat Pump Systems
| Older Through-the-Wall AC | Modern Heat Pump System |
|---|---|
| Basic cooling focus | Cooling + improved humidity control |
| Older coil designs | More advanced heat transfer |
| Less precise controls | Improved electronic controls |
| Higher energy use | Better overall efficiency |
| Comfort varies | More balanced indoor comfort |
🔄 Heat Pump Systems Do More Than Simply Cool
For many homeowners, the words heat pump immediately bring to mind winter heating. It is easy to understand this, as one of the biggest advantages of a heat pump is that it can both heat and cool from the same system. What is sometimes overlooked is that a heat pump in cooling mode is very much like a modern air conditioner. Heat is taken from inside the room and moisture is removed from the indoor air by the evaporator coil.
Newer heat pump systems often excel in the overall refinement of the equipment. The manufacturers are still pouring money into better compressors, electronically controlled fans, optimised refrigerant circuits and better airflow management. Those improvements not only help cut electricity use, but they also mean more consistent comfort inside the home. You're replacing older equipment and many homeowners notice the room no longer swings between too cold and too humid. Instead the temperature stays more steady and the air just feels lighter and more comfortable all day.
💨 Better Airflow Makes Better Humidity Control
The evaporator coil is not solely responsible for removing humidity. Airflow is a big factor too;If air is moving too fast over the coil, there might not be enough time for moisture to condense properly. If you have a clogged filter or dirty coil, the airflow is restricted too much and it affects cooling performance and makes the system work harder.
Modern through-the-wall heat pump systems are generally designed to provide much more consistent air flow than many older systems. With cleaner coils, better fan technology, and proper installation, you can balance the system better to provide efficient cooling and good dehumidification. I’ve seen cases where changing a long-neglected filter made a perceptible difference in indoor comfort, because the system could once again move air the way it was designed to; Good humidity control is not a function of one component.
It is the result of the whole HVAC system working together as its engineers designed it.
🌿 Jake's Mid-Article Advice
Whenever homeowners ask me why their house feels damp even though the air conditioner is running, I suggest checking these basics first:
- ✔ Clean or replace the air filter.
- ✔ Make sure indoor and outdoor airflow isn't restricted.
- ✔ Verify the condensate drain is working properly.
- ✔ Schedule routine maintenance if performance has declined.
- ✔ If the equipment is reaching the end of its service life, compare the comfort benefits of today's modern heat pump through-the-wall systems.
🏠 Why Proper Equipment Sizing Is Critical for Humidity Control
One of the biggest surprises for homeowners is learning that an oversized air conditioner can actually make a home feel less comfortable, even if it cools the room very quickly.
I hear it all the time.
"Jake, wouldn't buying the biggest unit available cool the room faster?"
Technically, yes.
But comfort isn't simply about how fast the temperature drops.
It takes time to remove humidity. Since warm indoor air continues to pass over it, moisture only condenses on the evaporator coil. If an air conditioner is too large it may cool the room too fast and the thermostat may "call off" the cooling cycle before enough moisture has been removed from the air.
The room is at the desired temperature, but the humidity is still high. That’s when homeowners say the room is cold but sticky. At the other end of the spectrum, an undersized unit may run continuously on hot days without ever catching up. Longer run times can dry things out, but the system is also working harder than it was meant to, using more electricity and causing longer-term wear on parts.
The goal isn't the largest air conditioner.
It's the right-sized air conditioner.
The Air Conditioning Contractors of America (ACCA) and other organisations recommend that you do proper load calculations that consider insulation, ceiling height, window orientation, occupancy, local climate and many other variables — not just room size.
Learn more:
- 🌎 ACCA Residential Design Resources: https://www.acca.org
📊 Properly Sized vs Oversized Equipment
| Properly Sized ✅ | Oversized ⚠️ |
|---|---|
| Balanced humidity | Sticky indoor air |
| Longer cooling cycles | Short cycling |
| Better comfort | Cold but clammy rooms |
| Improved efficiency | Reduced moisture removal |
| Longer equipment life | More frequent cycling |
⚙️ Modern Controls Help Maintain Better Comfort
One of the biggest differences between older through-the-wall air conditioners and many modern heat pump systems isn't always visible from the outside.
It's the controls.
Older equipment usually had relatively simple thermostats and basic control boards. Of course they did their job well for many years, but systems today can work a lot more precise. Improved electronic controls allow for more accurate regulation of compressor operation, fan performance and temperature sensing than many earlier designs.
The result isn't necessarily a colder room.
It's often a more comfortable room.
Many newer systems keep indoor temperatures more consistent with fewer large temperature swings between cooling cycles. That consistency helps to cut down on the feeling of the room constantly changing between warm, humid periods and too-cool blasts of air. Each manufacturer has their own system design philosophies, but electronics advances have become an important part of improving overall indoor comfort.
🌡️ Better Coil Design Improves Moisture Removal
Another place where HVAC technology has come a long way is the evaporator coil itself. The heart of removing humidity is the evaporator coil. The warm air inside the house touches the cold surface, cools down, and condenses the moisture. The moisture then runs away. Manufacturers have spent years perfecting coil designs that improve heat transfer, airflow distribution and overall operating efficiency. Homeowners seldom see these engineering improvements, but they can make a big difference in the comfort of everyday living.
Modern coils are designed to maximise surface area exposed to moving air while allowing efficient refrigerant flow. These changes, as well as improved blower performance and better airflow management, help the system to more effectively remove heat and moisture during normal cooling operation. Such improvements are often the reason homeowners tell me that their replacement system simply “feels better”.
🏡 Your Home Also Influences Indoor Humidity
No amount of good HVAC equipment can overcome conditions inside the home that constantly add excess moisture. I’ve seen homes where the air conditioner was doing exactly what it was supposed to do, but the moisture was still coming into the house faster than the equipment could remove it.
Common contributors include:
- 🚿 Long hot showers without exhaust fans
- 🍳 Frequent cooking and boiling water
- 🌿 Large numbers of indoor plants
- 🧺 Drying clothes indoors
- 🌧 Outdoor air leaks
- 🚪 Frequently opened exterior doors
In many homes, addressing these moisture sources improves comfort just as much as upgrading the HVAC system itself. That's another reason I always look at the entire home instead of focusing only on the air conditioner.
📊 HVAC System vs Home Environment
| HVAC Equipment ✅ | Home Conditions 🏠 |
|---|---|
| Removes heat | Generates moisture |
| Removes humidity | Introduces humidity |
| Improves comfort | Can increase moisture load |
| Controls temperature | Influences indoor conditions |
Comfort is always the result of both working together.
🧹 Maintenance Has a Bigger Impact Than Most Homeowners Think
Whenever someone tells me their air conditioner doesn't seem to control humidity like it used to, one of my first questions is surprisingly simple.
"When was the last time you cleaned the filter?"
It's amazing how often that question leads to a long pause.
Airflow is one of the worst enemies of efficient humidity removal. Dirty filters restrict the amount of air that can flow over the evaporator coil, making it more difficult for the refrigeration system to effectively pull heat out. Dirty coils, clogged outdoor grilles, and unmaintained condensate drains all contribute to degrading performance over time.
The U.S. Department of Energy suggests that routine maintenance on HVAC systems will keep them running efficiently and extend their life. This includes cleaning and replacing filters and making sure that airflow is not obstructed. Even modern heat pump through-the-wall systems need regular maintenance. They just work best if you let them work the way their manufacturers intended.
🌎 Energy Efficiency and Humidity Often Go Together
One of the interesting things I’ve noticed over the years, is that homeowners tend to compartmentalise efficiency and comfort into two separate topics.
They are connected.
“An HVAC system that effectively removes heat and humidity doesn’t have to work as hard to keep indoor conditions comfortable. Shorter recovery times and more consistent operation are the result of balanced airflow, cleaner coils, proper refrigerant performance and better controls.
Many newer wall-mounted heat pump systems are designed to meet higher energy efficiency standards than much older equipment. ENERGY STAR® qualified products meet independently established energy efficiency criteria to help consumers identify systems that are designed to use energy efficiently without sacrificing performance.
Learn more:
- 🌎 ENERGY STAR Heating & Cooling: https://www.energystar.gov
✅ Homeowner Humidity Checklist
If your home still feels damp even though the air conditioner is running, ask yourself these questions:
- ✔ Is the air filter clean?
- ✔ Has the system received routine maintenance?
- ✔ Is the condensate drain operating properly?
- ✔ Is outdoor airflow unrestricted?
- ✔ Does the equipment appear properly sized?
- ✔ Are windows and doors well sealed?
- ✔ Is excessive indoor moisture being generated?
- ✔ Is the air conditioner nearing the end of its service life?
If you answered "no" to several of these questions, there may be opportunities to improve both comfort and energy efficiency.
👨🔧 Final Thoughts from Jake
One thing I’ve learned in years of experience with through-the-wall HVAC systems is that homeowners don’t always ask for lower humidity.
They desire more comfort.
What they are really describing is a home that feels fresh rather than sticky, comfortable rather than damp, and balanced rather than constantly fluctuating between hot and cold. That’s the difference between today’s heat pump through-the-wall systems and many older air conditioners. They are not just designed to turn down the thermostat setting – they are built to deliver a more complete indoor comfort experience.
Of course, no HVAC system can fix every humidity issue on its own. Proper sizing, good installation, routine maintenance, unrestricted airflow and attention to indoor moisture sources all play an important role. But when those pieces click into place, the difference can be felt from the second you walk in the room.
If you’re replacing an older through-the-wall air conditioner, don’t just look at BTU ratings or energy efficiency. Ask about how the new system handles air flow, moisture removal, and overall indoor comfort. Those are the improvements that, in my experience, homeowners appreciate long after installation day has come and gone.
Jake Lawson
HVAC Insights Specialist
The Furnace Outlet
