A-1 Mechanical Blog: Posts Tagged ‘Dehumidifier’

Why Is My House So Humid?

Wednesday, June 26th, 2019
Air Conditioning

Michiganders understand high humidity is just one of the tradeoffs of living near the Great Lakes, but you may still ask “why is my house so humid?” Unfortunately, proximity to a water source like the Great Lakes increases the amount of moisture in the air and makes the air feel warmer, especially in the mornings.

Humidity tells you the moisture content, or how much water vapor is present in the air. When humidity is high, it feels muggy or “sticky” because sweat doesn’t evaporate easily.

Conversely, when humidity is low, your skin is drier and it’s easier to become dehydrated. Think of winter, when we’re indoors, the air is dry (and colder). We tend to have more issues with dry skin in the winter because more moisture evaporates from our bodies.

In this blog, we’ll review the difference between relative humidity and dew point, what is an achievable and recommended humidity level indoors and how your HVAC system works to control moisture.


Relative Humidity

The relative humidity is measured as a percentage. It defines if the air is saturated. If the relative humidity registers as 100 percent, for example, the air is saturated. If the percentage is 50, it means the air contains half of the water vapor required to be saturated.

As the amount of water vapor in the air increases, the relative humidity increases too. Now, if the temperature drops but the water vapor stays constant, the relative humidity goes up. If the temperature rises while the water vapor is the same, the relative humidity goes down.

Why? Because colder air needs less moisture to achieve saturation than warmer air. For example, in the morning, when the dew is still fresh on the grass, the relative humidity is higher. The morning air is cooler and closer to saturation.

Finally, cold air is denser than warm air, which leaves more room for water vapor in the warm air of summer.

Dew Point

Although you’ve probably heard someone say, “it’s not the heat, it’s the humidity,” dew point is actually a better marker of humidity because it’s not dependent on temperature.

The dew point is the temperature in which the air must cool in order to be saturated. Below the dew point, water condenses from the air to surfaces, like the morning grass. Because it’s not related to temperature, the dew point doesn’t change as much during the day. So, in short, the answer to why is my house so humid is simply the air is nearly or fully saturated.


When the humidity is high indoors, your home runs into certain risks including poor air quality. High indoor humidity often causes:

  • Mold and mildew growth
  • The right environment for dust mites to multiply
  • Insects and rodents seeking moisture. They leave behind droppings, nesting material and other particulates in your ventilation.
  • Cupping in hardwood floors and warping of wooden doors, door frames, and more
  • Uncomfortable living conditions for those with certain respiratory or cardiac conditions.

Humidity increases breathing difficulties for people with asthma, COPD, congestive heart failure and other conditions. Excess humidity increases allergy and asthma triggers like dust mites and mold and mildew spores.


Too much moisture in the air traps heat and makes it feel hotter than the actual temperature. Therefore, it’s important to invest in an air conditioner or heat pump to both cool and dehumidify your home. Michigan weather might be great for growing blueberries, but if it’s humid inside, it may be hard to be comfortable and sleep well.

Humans cool their bodies by sweating. However, if there’s a lot of water vapor in the air, sweat can’t easily evaporate off our skin. At 100 percent relative humidity, for example, sweat won’t evaporate at all because the air is already completely saturated with water vapor.

Many people have ceiling fans to cool their homes, however, it is important to understand that fans do nothing to cool the air. They, in fact, provide a breeze to help your perspiration evaporate easier. They don’t cool the air, they help you feel cooler.


Your air conditioning unit does more than just blow cold air into your home. It extracts heat and water vapor from the air to meet the temperature set by the thermostat. Inside your air conditioning unit are coils filled with refrigerant.

Refrigerant is a substance which moves back and forth between liquid and gas states to absorb and release heat. As the hot humid air from inside your home passes over these coils, the liquid refrigerant absorbs the heat and turns it into a gas.

To keep your home at a cool temperature, the air conditioner compresses the air inside the coils until it returns to liquid. The extra heat generated by compressing this gas releases outside the home via condenser coils and a second fan.


High humidity makes the inside of your home feel clammy. Fortunately, an air conditioning unit extracts moisture with an evaporator coil. As humid air passes over the evaporator coil, it condenses and drains into a condensate pan.

To avoid water damage, keep an eye on your condensate pan. If you find water around your indoor air handler or suspect a clog in the line, call A-1 Mechanical for assistance. A small amount of water can easily create thousands of dollars of damage.


If the high indoor humidity is too uncomfortable or compromising the health of a family member, call our team in Lansing or Grand Rapids for help. We’re proud to offer a range of heating and cooling services to our communities including air conditioner installation and AC service and repair. You won’t need to ask “why is my house so humid” again!

We also have a selection of indoor air quality products such as whole house dehumidifiers designed to work with your central heating and air. For a free estimate on new HVAC equipment or to book AC repair or service, call A-1 Mechanical at 517-348-0302.

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