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What You Need to Know
- The ideal humidity level for a home is between 30 and 50 percent.
- Excess humidity can lead to mold and mildew growth, as well as causing damage like peeling paint.
- Some potential reasons for a house being too humid include humid conditions outdoors, activities like washing dishes or showering, plumbing leaks, insufficient insulation, moist soil under the home, poor ventilation, and an AC unit that is too large.
- If the AC unit is indeed the incorrect size for the home, it’s a good idea to have an HVAC company fit the home with a more suitable model.
Q: My family recently relocated to a new home, and it feels incredibly muggy indoors. Our air conditioner seems to be working just fine, so why is my house so humid?
A: Figuring out why a house is so humid can take some troubleshooting, but it may prevent many issues in the future. But what is high humidity? According to Energy Star, the ideal indoor relative humidity should be between 30 and 50 percent—anything higher than 50 percent is considered high.
High humidity levels can cause discomfort and health issues, and excessive humidity can even cause damage in a home. Some telltale signs of excess moisture include an AC system that smells musty, a humid feeling in the house, or visible mold and mildew growth. Excess humidity in a house can also cause condensation on windows, toilet tanks, and pipes. Wondering what causes condensation? It happens when warm, moist air comes in contact with cool surfaces, and the vapor in the air turns into liquid water. Traces of moisture can spread to ceilings and walls, causing discoloration and mold growth. Peeling paint and creaking or buckling floorboards can also be a sign of excessive moisture.
Ultimately, high humidity levels have many different causes: climate, daily activities, HVAC issues, and poor ventilation are just a few of the culprits. Depending on the cause, the solutions can range from the purchasing one of the best dehumidifiers for the job, to servicing your HVAC or AC units. Read on to see if any of these issues may be present, and find out how to restore the home to a comfortable humidity level indoors.
The climate affects the humidity level in your home.
Climate can contribute to high humidity in a house. If it’s exceptionally humid outside, chances are it’s going to be muggy inside a home. The changing seasons and temperature can be significant factors for rising indoor humidity levels and the main culprit for an uncomfortable environment.
Some parts of the country are more prone to high humidity than others, and inside humidity levels tend to be higher in regions with muggy climates. The EPA offers recommendations on indoor humidity levels relative to outdoor temperatures, but as we said earlier, the 30 to 50 percent humidity range is the sweet spot.
Tried-and-True Advice
“As a plant person, I like my home a little more humid than average in order to appease my tropical companions. However, I own a split-level home, which means the lower half of my house is partially underground. Since we have humid, rainy summers, there’s an excess of groundwater in the summer and this leads to the basement level being uncomfortably humid.
We purchased a large-room dehumidifier to help abate the high levels of moisture. It’s very effective but it actually kicks off some heat: something you may not like if you’re trying to keep your home nice and cool on a hot day. For this reason, I’d highly recommend looking for a dehumidifier that can be programmed to run in shorter increments throughout the day rather than running it for an hour or more. It will work just as well and you won’t be warming up a room you’re trying to keep cool.”
—Amber Guetebier, Contributing Writer
Everyday activities like cooking, washing, and showering can contribute to humidity levels.
Humidity levels can be affected by daily household activities that can naturally add more moisture to the air: Cooking and running the dishwasher can add more water vapor to the air in the kitchen. Long, hot showers add a lot of moisture in the bathroom.
Keeping areas ventilated by opening a window or installing an exhaust fan can lower humidity inside the house. A professional can direct certain appliances, such as clothes dryers and stoves, to vent outside of the home. A whole-house dehumidifier costs about $1,500 on average and can also help eliminate some of the moisture created by these activities.
Leaks coming through cracks in the plumbing system may be the cause.
An interior plumbing leak from a bathroom or kitchen sink can cause increased moisture in the air. Make sure to check pipes often for cracks and corrosion; according to the EPA, leaks can lead to the growth of harmful biological pollutants. Early plumbing leak detection could help prevent water damage, musty smells, and potential mold growth.
While some leaks are easy to spot, others are not. Look for wall discoloration, bubbling paint or wallpaper, a dripping sound, or a musty smell. If any of these are present, you’ll want to contact a professional for plumbing leak repair.
Poor insulation could be increasing the home’s humidity levels.
Poor insulation can allow cold air to seep into a home during the winter, canceling out the efforts of a furnace. The same principle applies to humidity. When outdoor humidity is high, that damp air can make its way inside via gaps not sealed by insulation. This also means that cool, air-conditioned air can escape instead of circulating indoors. So while it may seem like the central AC is not blowing cold air, it actually may be working overtime (and driving up energy costs, too).
Having old insulation replaced, especially in the attic and basement, could be the key to eliminating excess moisture in the air. If it isn’t possible to completely replace the home’s insulation, caulking or sealing windows throughout the home can be another effective way to restore the home to a more ideal inside humidity level.
Moisture from soil under your home may be penetrating the house.
The dirt under and around your home may not be the first thing that comes to mind when you wonder why your house is so humid. However, humidity can come up through the soil underneath the foundation. This is called rising damp, and ineffective grading can be a significant factor since groundwater and rain can accumulate in a home’s foundation. Basements can be humid since they’re often poorly insulated and don’t have windows, and this can compound any issues.
Homeowners who live in a climate with excessive rain will want to ensure that gutters and downspouts work correctly and rainwater is directed away from the house to keep moisture out. Professionally installed awnings placed above windows and doors are an excellent way to keep water out as well.
A poor ventilation system may be to blame.
Adequate ventilation can help control a home’s humidity level, impacting health and a home’s structural integrity. If there are high humidity levels in your home, poor ventilation can be to blame. If you ventilation issues are behind your home’s high humidity levels, open windows and keep them open for extended periods for humidity control, particularly in high-moisture areas such as bathrooms and kitchens. You may also consider having a ventilation system professionally installed.
Your AC unit may be too big for the home.
Bigger isn’t always better: An oversized window or central AC unit may be the reason for excessive moisture in a home. The evaporator coil found inside the AC unit acts as a dehumidifier and pulls humidity from the air as it runs. If the unit is too large, however, it may cool a room or home too quickly, running for only 10 to 15 minutes on a hot day before it abruptly shuts down.
This is commonly referred to as short cycling, and a professional can diagnose the problem as part of an HVAC inspection. A longer runtime is needed to dehumidify a home correctly. While the cost of HVAC replacement may seem high to homeowners at first, investing in a smaller unit may make a home more comfortable and energy efficient in the long run.
Additionally, even if an HVAC or AC unit is the proper size, it can contribute to high humidity if it is not functioning properly. HVAC systems last from 15 to 25 years on average. In some cases, HVAC costs may be partially covered by a home warranty. If it’s been a while since the system has been serviced or it is reaching a fairly old age, calling one of the best HVAC companies might be your next step.
