What to Know About Humidity: Levels, Impacts, and Controlling

Written By Adam Paul - Waterproofing Expert

The humidity is the amount of water vapor present in the air space. It is expressed as a percentage. Humidity is measured by the hydrometer, and its SI unit is g/m3. Humidity is mainly of 3 types such as absolute humidity, relative humidity, and specific humidity. As well as humidity level is 3 main types such as too dry humidity, optimum (ideal) humidity, and too much humidity.

The ideal indoor humidity of a house should be between 30% and 50%. It helps to maintain good health and comfort for the residents without any structural issues or water damage. If it falls below 30% considered a too dry humidity condition, while it increases more than 60% considered too much humidity level in the home. Both of them affect negatively to the residents and the home structure by increasing damage to the home structure and increasing health effects to the residents.

You can identify a humidity problem in the home by condensation, musty odors, mold and mildew growth, paint peeling and bubbling, warped floors and swollen doors, clammy or sticky indoor air, and visible water stains on drywall and ceiling tiles. These humidity signs occur due to plumbing leaks, ground water intrusion, improper ventilation, improper dryer vent discharging, daily activities, and leaky doors and windows in the home.

Higher humidity negatively affects the house interior. It accelerates mold growth, metal corrosion, paint damage, pest infestation, higher energy consumption, and damage to wood and furniture over time. To prevent these problems, you can use materials like ceramic tile, PVC, fiberglass, stainless steel, and moisture-resistant drywall.

To control the higher humidity in the home, Aqviz highly recommends installing a waterproofing membrane on the basement, foundation, roof, slabs, balconies, and other possible water-leaking and penetration areas. In addition, you can use a dehumidifier, sealants, and exhaust fans, improve insulation, repair leaky plumbing, and maintain the proper temperature in the home.

What is the Definition of Humidity?

The definition of humidity is the amount of water vapor present in the air. Humidity is usually expressed as a percentage. It is measured by using a hydrometer. The SI unit of humidity is g/m³. The humidity is mainly of 3 types, such as absolute humidity, relative humidity, and specific humidity. The humidity level can vary with the weather, temperature, and location.

The humidity level can be increased or decreased. If the humidity level is too low, it can cause dry skin, irritate the nasal passages and throat, and make the eyes itchy. If the humidity is too high, it can make the air feel stuffy or damp and can cause condensation on walls and floors, which can lead to mold growth. Hence, it is important to maintain a normal humidity level in the house.

What are the 3 Types of Humidity?

The humidity is mainly of 3 types, such as absolute humidity, relative humidity, and specific humidity.

Absolute humidity: Absolute humidity is a measurement that describes the mass of water vapor per unit volume of air. It is expressed in grams of moisture per cubic meter of air (g/m3). This measurement is not affected by temperature or pressure, unlike relative humidity. It’s used in weather forecasting and understanding climate.

Relative humidity: Relative humidity is a measurement of the amount of moisture in the air compared to the maximum amount of moisture the air could hold at the same temperature. It is expressed as a percentage (%). For example, if the air is holding half the moisture it could potentially hold, the relative humidity is 50%. High relative humidity indicates that the air is saturated with water vapor, and can often create uncomfortable dampness.

Specific humidity: Specific humidity is a measurement that represents the actual amount of moisture in the air, irrespective of the temperature. It is usually expressed in grams of water vapor per kilogram of air. Unlike relative humidity, the specific humidity doesn’t change with temperature or pressure; it only changes when water is added or removed from the air.

What is the Ideal Indoor Humidity Level of a House?

According to the National Library of Medicine, the ideal indoor humidity of a house should be between 30% and 50%. Ideal humidity helps to maintain good health and comfort for the residents. It prevents water damage in the structure and increases the energy efficiency in the home.

What are the Humidity Levels and Their Impacts?

Humidity levels are mainly of three types: Too dry humidity, optimum (ideal) humidity, and too much humidity are them. Below are their indoor effects.

Too Dry Humidity: Too dry humidity occurs when indoor relative humidity falls below 30%. These are the main 3 negative impacts of too low humidity.

Too dry humidity causes dry skin, irritated eyes, and aggravated respiratory problems among occupants
Insufficient humidity causes cracking and shrinking of wooden floors, furniture, and window frames
Too dry humidity causes paint peeling and drywall brittleness

Optimal (ideal) Humidity: Optimal humidity is considered between 30%-50% indoor humidity level in the home. These are the advantages of optimal humidity.

Optimal humidity increases comfort and health for residents, reducing allergens and dust mites
Proper humidity level prevents mold and mildew growth on surfaces and within walls
Ideal humidity improves the energy efficiency of heating and air conditioning systems like Trane and Carrier
Optimal humidity enhances the durability of building materials such as plaster, tile, and hardwood flooring

Too much Humidity: Too humid conditions begin when indoor relative humidity rises above 60%. These are the negative impacts of too humid conditions in the home.

Too much humidity accelerates the deterioration of insulation materials like fiberglass and cellulose in the home
Extra humidity promotes the toxic mold in the house
Extreme humidity corrodes indoor metal fixtures, fasteners, and HVAC components over time
Higher humidity increases the musty odors and indoor air contamination, affecting air quality measured by IAQ monitors

What are the 7 Signs of High Humidity In the House?

Here are 7 common signs of higher humidity in the house and where each typically appears in the home.

Condensation on windows and glass doors in bedrooms, bathrooms, and kitchens signals high humidity accumulating inside.
Musty odors in basements, crawl spaces, or behind walls indicate moisture buildup supporting mold activity due to high humidity content.
Mold spots and black mildew patches on bathroom tiles, ceilings, and basement corners thrive in saturated humidity conditions.
Peeling paint and bubbling wallpaper on the interior walls of living rooms and stairwells reveal persistent moisture caused by elevated humidity levels.
Warped wood flooring and swollen doors in living areas or hallways are signs of excess moisture content absorbed from humid air.
Clammy or sticky indoor air in closed bedrooms and poorly ventilated kitchens reflects high absolute humidity, making the space feel warmer.
Visible water stains on drywall or ceiling tiles in basements or upper-level bathrooms suggest long-term exposure to high humidity values.

What are the 6 Causes of Humidity In the House?

These are the six major causes for higher humidity levels inside residential buildings.

Humidity level increases due to leaking plumbing lines under sinks, inside walls, or beneath concrete slabs.
Indoor humidity level increases due to groundwater intrusion from the unsealed basement walls and foundation cracks
Humidity level increases due to improperly vented bathroom exhaust fans and kitchen range hoods. These can trap the steam and vapor due to improper fixing.
High humidity often builds up when dryer vents discharge moist air indoors or become clogged with lint.
Humidity level increases due to everyday activities like cooking, boiling water, and showering without proper ventilation systems
Another way of humidity level is leaky windows and doors, and an uninsulated attic space.

What are the Negative Effects of Humidity In the House?

Here are 6 major negative effects caused by higher humidity inside a house

High humidity content accelerates mold and mildew growth on surfaces like drywall, wood beams, and insulation.
Extreme humidity levels can corrode metal fixtures, HVAC ducts, and electrical components, shortening their lifespan.
High humidity levels cause paint peeling, plaster cracking, and the weakening of structural materials in walls and ceilings.
High humidity increases the dust mite infestations, worsening allergies and respiratory illnesses for residents.
Uncontrolled higher humidity raises indoor temperatures, forcing air conditioning systems like Lennox and Goodman to consume more energy.
Prolonged higher humidity causes leads to wood warping and floor buckling in hardwood floors, damaging the home’s interior aesthetics.

What Materials are Best for Higher Humidity in the House?

Here are 5 materials we recommend for homes with higher humidity values, based on our extensive field experience.

Ceramic tiles: Ceramic tiles resist moisture absorption, making it an ideal choice for flooring and wall surfaces in areas exposed to fluctuating humidity content.
PVC trim and molding: PVC trim and molding withstands warping, swelling, and rotting even when exposed to high relative humidity inside bathrooms, basements, or kitchens.
Fiberglass insulation: Fiberglass insulation, like Owens Corning, maintains thermal performance without absorbing moisture, helping stabilize indoor humidity values.
Stainless steel: Stainless steel fixtures resist corrosion and staining in environments with persistent high humidity levels, especially in laundry rooms and basements.
Moisture-resistant drywall: Moisture-resistant drywall (often branded as Greenboard or Purple Board) has a special coating that prevents mold growth even when humidity attributes peak.

These materials are highly recommended for basements, bathrooms, and coastal homes where the humidity level is high.

How to Control Humidity in the House?

Here are 6 effective ways to control elevated humidity inside a house

Install a whole-house dehumidifier like Aprilaire or Honeywell to automatically regulate humidity values across all living spaces.
Seal basement walls, crawl spaces, and foundation cracks with waterproof coatings such as Sika or Drylok to prevent groundwater vapor from increasing indoor humidity content.
Use exhaust fans in bathrooms, kitchens, and laundry rooms to immediately remove excess moisture and stabilize relative humidity after moisture-producing activities.
Improve attic insulation and add proper ventilation systems like ridge vents and soffit vents to block outdoor humidity infiltration during humid seasons.
Repair or replace leaky plumbing fixtures and drain lines to eliminate hidden sources of water that elevate absolute humidity over time.
Maintain consistent indoor temperatures using smart thermostats like Nest or Ecobee to reduce dew point issues and discourage condensation inside wall cavities.

Read More About: 10 Ways to Stop Severe Water Damage in the House

Are Humidity and Moisture Different?

Yes, humidity and moisture are different. Humidity is the amount of water vapor present in the air, while moisture is the presence or amount of liquid water.

Humidity is the amount of water vapor present in the air. It is usually expressed as a percentage. It expresses the amount of moisture the air is holding compared to the maximum amount it could hold at a particular temperature.

On the other hand, moisture is the presence or amount of liquid, especially water, in a substance, object, or environment. It can be present in different formations, such as in the soil, in the air, or within objects like clothes or food.

What is the Relationship Between Humidity and Temperature?

There is an inverse proportional relationship between humidity and temperature. When temperature increases, the air’s capacity to hold water vapor also increases, so the humidity may decrease even if the amount of water vapor stays the same. When the temperature drops, the capacity of the air to hold water vapor decreases, and the humidity increases

As a result of this, high humidity often makes people feel uncomfortable, especially in hot weather, while low humidity can cause dry skin and other discomforts. In summer, the air’s capacity to hold water vapor is higher than in winter, so the humidity is often lower in summer than in winter.