Why is my home 72 degrees, but it still feels hot and sticky?

We explain what causes this and ways to fix it.

The Gateway Arch and St. Louis, Missouri Skyline from Cahokia Mounds.

Have you ever heard someone say “It’s not the heat, it’s the humidity that gets you!” In the St Louis area, this phrase often comes up during the warmer months of the year. Air conditioning (AC) units will cool your home’s temperature down, but it still feels very uncomfortable because your home’s humidity isn’t being removed properly.

The most common misconception is that bigger is better!

If your AC is too big for your home, it doesn’t run long enough to remove the inside humidity. In the HVAC industry, we call this “Short Cycling”. What we mean by this is that the AC will cool off the home very quickly, but it has not run long enough to remove the inside humidity. If you look at your furnace, you will see a drain tube coming off of it. This tube is connected to the AC coil’s drain. This tube drains the water that accumulates on the coil from removing the home’s humidity.

Existing AC systems in a typical home will take about five minutes of running to even begin to remove the humidity in your home. If the system is too large, it may only run five to ten minutes and then shut off. In this case, the system doesn’t run long enough to remove the inside humidity.

The first thing that should ALWAYS be looked at is the sizing of the AC equipment. Many times when we arrive at an appointment, the first words out of a home owner’s mouth are “I need a bigger AC.” We always respond, “maybe not”. After getting the confused look from the homeowner, the next thing we say, “your current unit might actually be too big”. The only way to determine the right size is to do a PROPER load calculation on the home. This entails actually measuring the size of the home, determining the insulation levels of the home, measuring the size of the windows and doors, and finally which way the home faces. You cannot just go off the home’s square footage alone and nothing else. All of this information should be put into a load calculating software to determine the proper sizing of the HVAC system. A home that faces North and South usually will need a smaller AC than a similar home facing East and West. The windows on the home facing East to West have more sun shining into them which is going to heat the home more.

A great example of why having the right size matters for removing humidity is when there are three days in a row of 90+ degree weather and your home doesn’t feel comfortable until day three. Day one, your AC system short cycles and only runs for short periods of time to cool the temperature down and not remove the humidity inside. Day two, the home’s AC has been running for a day now doing these short cycles and has accumulated enough time to begin to remove some of the humidity inside. Day three, your home’s AC is finally starting to catch up and the relative humidity inside your home starts to really lower. FINALLY!    

York Affinity Series Condenser With A Multi-Stage Compressor

Multi-Stage Equipment

A new technology that is starting to see widespread application in homes is multi-stage (variable capacity) furnaces and air conditioner equipment. Basically a multi-stage system will shift gears and run as a smaller unit and extending the system’s runtime and raise energy efficiency. Longer run times will pass more air volume through the system and change your home’s temperature and humidity.

One of the best examples of this technology has been in your car for years. When you first get into your car on a hot day, you turn the AC to the coldest possible setting, and then you turn the fan speed to high. As the car begins to cool down, you will turn the fan speed down. Eventually, you will also adjust the temperature setting (capacity), because the car’s temperature and humidity are now comfortable and the A/C is able to maintain comfort at the lower levels. 

Advanced multi-stage home HVAC systems that are available now, will do all of this for you automatically. What happens is once the AC hits the desired temperature setting, a multi-stage system will automatically lower the fan speed of the blower and adjust the outdoor AC condenser’s capacity to save energy without human interaction, but still continue to de-humidify the house. The system’s energy consumption is a great benefit, but a multi-stage system is far superior at maintaining the desired temperature setting WHILE removing more humidity than a single-stage system.

Some other issues that can make you feel uncomfortable.

There are other issues that can add humidity into your home and cause comfort issues. These issues are less prevalent than oversized systems but include:

  • Insufficient air flow or return air flow
  • Excessive activities that add humidity to a home like indoor plant grow setups, boiling water on a stove, etc. 
  • Whole house or portable humidifiers in use during the summer months
  • Basements or crawl spaces with standing water or excessive moisture problems

That feeling of comfort when a system is sized properly for your home is LIKE LIVING IN HEAVEN.

If you have any issues like what we described above, call Energy Stars Heating & Cooling for a free in-home consultation. One of our certified Energy Consultants will measure your home or building, take notes about your equipment’s specifications, and run a free load calculation for you. Then they go over their findings and show you options that will make your home more comfortable and energy efficient all year round!