Water can destroy homes—not only in floods or heavy rains but also through self-inflicted ways that can be controlled entirely, stopped, and eliminated with a little effort. Depending on how well these steps are followed, this often doesn’t require insulation work. 

Understanding High Humidity in a Chicago Home

In a Chicago home where the air conditioner is rarely used, it’s important to understand the effects of high humidity (above 60%). Let’s first define humidity and why it matters.

What is Humidity?

Humidity refers to the amount of air moisture (water vapor). It’s usually measured as a percentage called **relative humidity (RH)**, which shows how much moisture the air is holding compared to its capacity. For example, 50% RH means the air holds half the moisture it could at that temperature.

Humidity influences how we feel, our homes, and our health. In cities like Chicago, where summer is hot and muggy and winters are cold and dry, managing indoor humidity can be challenging—especially without air conditioning.

Impact of Humidity in a Home Without Air Conditioning (Or someone in the home prefers to set the thermostat so that the AC only comes on when the temps in the house are above 80 degrees)

(Your AC is also a Dehumidifier!)

1. Physical Comfort and Perception of Heat
   

   Humidity affects how hot or cold we feel. As temperatures rise in Chicago in the summer, humidity levels also increase. Here’s why that matters:

   – High humidity makes it feel hotter: When the air is saturated with moisture, it’s harder for sweat to evaporate and cool our bodies. As a result, we feel hotter and stickier than we would at lower humidity levels.

   – Heat index: Humidity combined with high temperatures creates a “heat index”—the perceived temperature. For example, an actual temperature of 85°F with 70% humidity can feel like 95°F. The home can become uncomfortably hot without air conditioning to remove moisture from the air.

2. Effects on Indoor Air Quality and Health

   Humidity doesn’t just make the house feel warmer; it also impacts air quality and health.

   – Mold and mildew growth: High humidity encourages mold and mildew, especially in basements, bathrooms, and around windows. Mold spores can trigger allergies, asthma, and other respiratory issues. Prolonged exposure can lead to more serious health concerns. (See blog on mold. Don’t panic! Most homes have some mold, but only a few cases are severe enough to require action.)

   – Increased allergens and pollutants: High humidity can make the air stagnant, allowing pollutants like pet dander, pollen, and volatile organic compounds (VOCs) to linger. Without ventilation or an air conditioner, these pollutants can worsen air quality and make breathing more difficult. (Avoid installing attic fans; see blog on why they’re bad.)

3. Impact on Furniture, Walls, and Structure
   

   Humidity affects not only people but also the home and belongings.

   – Wooden furniture and floors: Wood absorbs moisture. In high humidity, wooden floors, doors, and furniture can swell and warp, causing doors to stick and floors to buckle.

   – Peeling paint and wallpaper: Moisture can seep into walls, leading to peeling paint or loose wallpaper—signs of more serious moisture issues inside the walls.

   – Condensation on windows and walls: Humid air condenses on cooler surfaces like windows or poorly insulated walls, leading to water damage over time and potentially causing mold and structural damage.