Iowa summers are notoriously humid. When that outdoor humidity creeps inside—or your home generates its own moisture—you're left with foggy windows, musty smells, and that uncomfortable sticky feeling. Here's what's happening and what you can do about it.
Iowa Humidity Facts
Iowa's average summer humidity is 65-75%, among the highest in the Midwest. When it's 85°F with 70% humidity, the “feels like” temperature is actually 93°F—that's the heat index effect.
Why Is Your House So Humid?
Iowa's Climate
Iowa summers are naturally humid, with average summer humidity of 65-75%. Air from the Gulf of Mexico brings moisture north, making our summers feel much hotter than the temperature alone.
Oversized AC
An AC that's too large cools quickly but shuts off before properly dehumidifying. Short cooling cycles don't give the system time to remove moisture from the air.
Fan Set to 'On'
When your thermostat fan is set to 'on' instead of 'auto', moisture collected on the evaporator coil evaporates back into your home between cooling cycles.
Poor Ventilation
Bathrooms and kitchens without proper exhaust fans add moisture. Tightly sealed modern homes can trap humidity inside without adequate ventilation.
Basement Moisture
Iowa basements often have moisture issues due to high water tables and humid soil. This moisture can spread throughout your home through the HVAC system.
AC Issues
A dirty evaporator coil, low refrigerant, or malfunctioning AC components can reduce dehumidification capacity even while still cooling adequately.
The Problem with High Humidity
High humidity isn't just uncomfortable—it causes real problems:
- Mold and mildew growth (health hazard and structural damage)
- Dust mites thrive (allergen problems worsen)
- Wood floors, furniture, and trim can warp
- Paint and wallpaper may peel or bubble
- Your home feels hotter than it is, leading to higher AC bills
- Electronics and appliances can be damaged by moisture
Solutions for Iowa Home Humidity
1. Check Your Thermostat Fan Setting
Make sure your thermostat fan is set to “Auto” not “On.” When set to “On,” the fan runs continuously, blowing moisture back into your home between cooling cycles.
2. Use Exhaust Fans Properly
Run bathroom exhaust fans during and for 15-20 minutes after showers. Use your kitchen range hood when cooking, especially when boiling water. Make sure these fans actually vent outside, not into your attic.
3. Schedule AC Maintenance
A well-maintained AC removes humidity effectively. Dirty coils, low refrigerant, or other issues can reduce dehumidification capacity. Annual tune-ups keep your system working properly.
4. Consider a Whole-House Dehumidifier
For persistent humidity problems, a whole-house dehumidifier is the most effective solution. These units work with your HVAC system to maintain consistent humidity levels throughout your home.
Whole-House Dehumidifier Benefits
- • Maintains consistent 40-50% humidity throughout home
- • Works independently of AC (even in spring/fall)
- • Drains automatically—no buckets to empty
- • Can reduce AC runtime and energy costs
- • Protects your home from moisture damage
5. Address Basement Moisture
Iowa basements are notorious for moisture issues. Consider:
- Running a basement dehumidifier year-round
- Sealing foundation cracks
- Improving gutter drainage away from your foundation
- Using vapor barriers if you have a crawl space
Is Your AC the Problem?
If your AC cools your home but leaves it humid, the problem might be:
- Oversized AC that short-cycles (runs briefly, then shuts off)
- Dirty evaporator coil reducing moisture removal
- Low refrigerant affecting dehumidification capacity
- Incorrect fan speed settings
- Aging system losing efficiency
Our technicians can evaluate your AC's dehumidification performance and recommend solutions—whether that's a tune-up, system adjustment, or adding a dedicated dehumidifier.
Frequently Asked Questions
What should indoor humidity be in Iowa summers?
Ideal indoor humidity is 30-50%. During Iowa summers, aim for 40-50%. Below 30% feels too dry and can cause respiratory irritation; above 50% promotes mold growth and dust mites. Most thermostats with humidity displays or a $10-20 hygrometer can help you monitor levels.
Why isn't my AC removing humidity?
Your AC may not be removing humidity if it's oversized (cools quickly but doesn't run long enough to dehumidify), the fan is set to 'on' instead of 'auto', the evaporator coil is dirty, refrigerant is low, or the system needs maintenance. A properly functioning AC should remove humidity during normal operation.
Do I need a whole-house dehumidifier in Iowa?
Many Iowa homes benefit from whole-house dehumidifiers, especially those with finished basements, older construction, or oversized AC systems. These units work with your HVAC system to maintain consistent humidity levels throughout your home, often running when the AC doesn't need to.
Will a dehumidifier lower my energy bills?
Yes, properly controlled humidity can reduce energy costs. Dry air feels cooler, so you can set your thermostat higher while feeling the same comfort level. A whole-house dehumidifier typically costs $150-300/year to operate but can save you more in AC costs.
What are signs of too much humidity in my home?
Signs of high humidity include foggy windows, musty odors, visible mold or mildew, peeling wallpaper or paint, warped wood floors or furniture, allergies or respiratory issues flaring up, and a general clammy or sticky feeling in the air.