The best indoor relative humidity level for your home is 30–60% RH. The U.S. Environmental Protection Agency (EPA) recommends this range to prevent virus, bacteria, and other pathogen transmission. Additionally, this range feels the most comfortable, will help maintain your home, and will prevent mold and mildew growth. Excess humidity (a high amount of water vapor) can make us feel warmer during the summer and colder during the winter months.
Indoor relative humidity affects your comfort. Here’s a simple way to think of what “percent relative humidity (% RH)” means — it is a measure of how much moisture there is in the air compared to how much there could be. This percentage takes into account the temperature of the air, too, as warmer air can hold more water than cooler air. In other words, it is “relative” to temperature.
As a professional HVAC technician, I always stress the importance of monitoring and maintaining a solid indoor air quality strategy with a strong emphasis on humidity control. Maintaining ideal indoor humidity levels is essential for comfort, health, and safety. Your HVAC system plays a crucial role in humidity control, and a professional heating and air conditioning service provider is an excellent resource for help. If you’re unsure, we reviewed the best HVAC companies to help.
If you find your home drier than ideal for your comfort, let the professionals evaluate your indoor air quality and discuss whole-home humidification:
Why Does Your Home’s Humidity Level Matter?
Maintaining ideal indoor humidity levels matters because it’s central to occupant comfort, health, and safety. Excessive moisture can facilitate the growth or spread of harmful bacteria, viruses, mold, or other microbial growth. The Massachusetts Institute of Technology (MIT) found a correlation between indoor moisture levels and COVID-19 transmission. High indoor relative humidity can result in condensation issues, resulting in substantial repair costs if not addressed.
On the other end of the spectrum, having dry air comes with its own set of problems. Too little humidity can result in dryness and irritation to the eyes, throats, and sinuses. Your skin may become flaky and easily inflamed. Certain construction materials, furnishings, flooring, and artwork may become damaged. There are several ways that indoor humidity affects your health and home.
What Humidity Level Is Ideal for Your Home?
According to the U.S. Environmental Protection Agency (EPA), the ideal indoor relative humidity is between 30% and 50% RH — and must be kept below 60% RH. Interior factors such as occupant activity levels, cooking, showers, and laundry, plus exterior elements such as outdoor temperature and humidity (which can be exacerbated by home air leakage rates) affect indoor humidity levels. Outdoor relative humidity varies drastically by region.
How Can You Measure Your Home’s Humidity Levels?
Before I can help my clients hone in on a comfortable humidity level, we need to measure the moisture in their indoor air. During your annual HVAC system maintenance visit, your technician will likely use specialized test instruments. Still, you can measure the relative humidity in your indoor air without breaking the bank on fancy gadgets.
Check out your thermostat for humidity indication! Many modern programmable and smart thermostats record and display indoor relative humidity percentages. Depending on the quality and location of the thermostat, this may not accurately represent actual indoor humidity levels across the space. Still, it can serve as a ballpark reference point.
If your thermostat is from the Dark Ages and won’t show your indoor humidity, don’t fret! Digital hygrometers (typically dual function with temperature) are available in various types and styles, starting at just $10 to $15. Look for a model with a published humidity accuracy range of no higher than +/- 3% relative humidity (RH).
Digital hygrometers are typically highly user-friendly. Feature-rich models might have a button or two that scrolls between different display values, but once you figure out the device navigation, it’s as simple as placing it somewhere in your home and watching the numbers. While you can move the hygrometer around to various areas of your home, you can often obtain an excellent single-point reading near the central return grille connected to your heating and air conditioning system.
Digital Hygrometer / Thermometer
What Factors Commonly Affect the Indoor Humidity Levels of a Home?
Various factors routinely affect indoor humidity levels in a home, although some are easier to identify than others. Here are the most common contributing elements I see in clients’ homes:
- Building Envelope: There’s no need to travel to the mailbox or post office. We’re talking about your home’s construction envelope. Inadequate insulation or sealing can negatively impact temperature and humidity.
- Indoor Temperature: Where do you keep your thermostat set? Remember that warmer saturated air can hold more moisture than cold air, which means the relative humidity percentage can change with the temperature – even without an actual change in the amount of water vapor.
- Ventilation System: A properly designed and balanced fresh air ventilation strategy is imperative to achieve the best humidity levels. Ask your HVAC technician to review your home’s current ventilation strategy and ensure it’s up to par.
- Occupant Activity: If you’re breathing inside your home right now, you’re increasing your relative humidity. Each additional occupant in your home contributes to indoor moisture levels, as does boiling water, taking hot showers, washing clothes, etc.
- Houseplants: Plants release approximately 97% of the water they receive into the air as water vapor. Having a high number of indoor plans can increase relative humidity notably.
- HVAC System Performance: Keep up with annual air conditioner tune-ups. Your air conditioning system must run efficiently to maintain ideal humidity levels in your home.
If you have concerns about your home’s indoor humidity, contact a top-rated HVAC service provider for professional assistance.
How Can You Raise Your Home’s Humidity Levels? (5 Tips)
You can raise your home’s humidity level through a combination of outdoor and indoor house treatments and living habits. Low humidity causes dry skin, sore throats, and static electricity. Frequently running gas heating systems during cold winters can dry things out even more. Here are four tips to raise the humidity.
1. Whole-House Humidifier
Installing a whole-house humidifier is the best way to maintain consistent relative humidity. This humidifier works with your heating and air conditioning unit blower to add moisture to your indoor air by introducing hot steam or a cool mist. Whole-house humidifiers frequently require a connection to your home’s water supply and a drain line to the home’s exterior, and some require dedicated 120- or 240-volt electrical circuits. Commonly controlled by an indoor humidistat, whole-house humidifiers will add moisture to the air until it reaches the relative humidity percentage of your choosing. Whole-house humidifier installation costs vary based on several factors, but the national average is around $2,250. Typically, homeowners can expect to spend between $900 and $3,600 on a professional whole-house humidifier installation.
Portable humidifiers are also available to add moisture to individual rooms. While these are typically much less expensive than whole-house humidifiers, you may need multiple portables to increase the relative humidity in large homes.
2. Seal and Insulate
Air infiltration, or unintentional airflow into a building, can impact your ability to maintain ideal indoor humidity levels at home. According to ENERGY STAR, taking measures like sealing behind door and window trim and sealing and insulating your attic or crawlspace can reduce total air infiltration by 25% and save up to 10% on your annual energy bills. Costs for sealing and insulating vary widely depending on the size of your home and the scope of work required. Homeowners should expect to spend between $50 and $3,000 for home sealing and insulating.
3. Add Houseplants
Having a green thumb is a great way to add moisture to your home’s air. The average houseplant is quite generous, only retaining about 3% of the moisture it receives while releasing the remaining 97% back into the air. While there are many species of plants to choose from ranging in size and price, spider plants are among the most popular due to their known ability to increase indoor moisture and the minimal care required to thrive. Homeowners can typically expect to spend between $15 and $50 for a spider plant.
4. Hot Showers
Taking hot showers with your bathroom exhaust fan off and the door open (if privacy allows) is a great way to add moisture to your indoor air. The associated cost is limited to the utility costs for the water and heating it. If you have teenage daughters who frequently turn the bathrooms into saunas like mine, your home may already have plenty of indoor moisture.
5. Cook
Any type of cooking adds moisture to the air when it releases as steam from the food. Besides saving you money compared to takeout, you can humidify your home and enjoy a bowl of pasta at the same time. That said, unless you’re cooking frequently and for a large number of people, cooking won’t be enough to have a strong impact on your whole home’s humidity levels.
Whole-House Humidifier
How Can You Lower Your Home’s Humidity Levels? (5 Tips)
There are times when you need to lower your home’s humidity. Efficient airflow and water management are the two biggest factors to keep levels in check — and they’re important.
High humidity levels over prolonged periods will cause mildew and mold growth and can result in serious health issues. Humid air helps dust mites and allergens thrive and reduces the life of your AC unit filters. Here’s how to combat excessive indoor humidity and maintain ideal levels.
1. Whole-House Dehumidifier
Installing a whole-house dehumidifier is the best way to remove excess humidity from your indoor air. Unlike whole-home humidifiers that add moisture to the air, whole-house dehumidifiers use the refrigerant cycle to remove humidity and drain it outside your home. Typically integrated with your home’s HVAC system, you can install many common models in stand-alone applications for installation versatility. Whole-house dehumidifiers typically require dedicated 120 or 240-volt electrical circuits and a drain line to the home’s exterior. Pricing can vary by model and installing contractor, but homeowners typically expect to spend between $1,100 and $2,900 for the product, installation materials, and labor.
Portable dehumidifiers are also available to remove moisture from individual rooms. While these are typically much less expensive than whole-house dehumidifiers, they don’t draw out nearly as much moisture and require manually emptying the water reservoir.
2. Exhaust Fans
If your home is only a few decades old, you likely have a kitchen hood vent fan and at least one bathroom or utility room exhaust fan. Running these fans will exhaust stale and humid air from your home and draw in fresh air from outside. Remember that if your current outdoor relative humidity is higher than the humidity inside your home, operating exhaust fans can work against you by increasing indoor humidity levels. If you live in a muggy or coastal environment, Tip 3 below might be a better option.
3. Ventilation System
Ventilation systems are suitable for high-humidity regions and provide a controlled, filtered, and tempered air exchange between your house and the outdoors. Frequently integrated with your home’s HVAC system, balanced ventilation systems such as energy recovery ventilators (ERVs) or heat recovery ventilators (HRVs) will remove a specified amount of stale, humid air from your home while simultaneously supplying the same amount of fresh air back to the space. Unlike standard ventilation options, ERVs and HRVs remove humidity from the incoming fresh air, so it’s possible to ventilate effectively even during high outdoor humidity conditions. For extra high-humidity conditions, ventilating dehumidifiers are another option for simultaneous dehumidification with ventilation from a single product. Ventilation systems require careful attention to detail during the specification and installation process, so consult your local HVAC professional for assistance. Pricing varies by system type and installation requirements, but homeowners should expect to spend between $900 and $4,200 for a new ventilation system installed by a licensed professional.
4. Mindful Water Usage
Living in a desert climate, most of my clients’ humidity issues result from their indoor water usage habits combined with tightly constructed modern homes that trap excess moisture. Avoiding excessively long hot showers, operating exhaust fans during showers and kitchen range fans during cooking, and reducing the frequency of laundry and dishwashing can all play a part in minimizing the amount of moisture added to your air.
5. Open Your Windows
You can reduce your home’s indoor humidity levels by simply opening many or all of your windows. However, you’ll want to check the outdoor relative humidity levels first. It needs to be a lower humidity level outdoors than in your home for this to work. Check your weather app and compare the indoor and outdoor levels. If it is 40% RH outdoors and 65% RH indoors, then letting your home breathe will decrease its humidity in no time!
Signs Your Home Has Humidity Issues (5 Signs)
Besides buying a digital hygrometer to measure your home’s humidity levels, you can look for these signs of humidity issues in your home:
1. Wet Mirrors and Windows
Fog on the inside of your windows and mirrors and a strong indication there’s too much moisture in your home. That said, if you just took a long, hot shower in the bathroom, I wouldn’t worry about the condensation in your bathroom. If it persists throughout the day, though, you need to address it.
2. Stale, Musty Smells
Mold and mildew smells are another sign you have excessive humidity levels in your home. These smells usually come from mold and mildew growing somewhere in your home — bathrooms, basements, and kitchens are common areas, but they can also form inside your ductwork.
3. Visible Mold
If your home’s humidity levels stay too high for long periods, you might start to see mold growing on walls, ceilings, or other surfaces. Mold looks like black spots and often grows where there isn’t much airflow and wet areas. If you see mold, it’s important to deal with it fast so it doesn’t spread and cause health problems.
4. Wallpaper Peeling or Paint Blistering
Too much moisture in your home can also cause wallpaper to peel or your paint to blister. These problems happen more often in rooms that get a lot of moisture, like kitchens and bathrooms.
5. Worsening Allergies or Breathing Problems
High humidity levels can make you feel sick — especially if you have allergies or breathing problems. Mold, bacteria, viruses, and other pathogens thrive in moist environments and can trigger your allergy symptoms and make it harder to breathe. On the other hand, low humidity levels can lead to cracked lips, dry sinuses, red eyes, and itchy skin.
Bottom Line: Should You Need To Adjust Your Home’s Humidity Level?
If you aim to maintain ideal indoor humidity between 30 and 50% RH, the average home will require some help. Modern home construction is becoming increasingly tight, making excess humidity a factor even in my clients’ harsh desert climate. Missing the mark on your home’s indoor humidity levels can lead to poor indoor air quality (IAQ) and severe health concerns.
If you’re worried that your home could have a humidity issue or an underperforming air conditioning system, reach out to a professional HVAC contractor for help:
FAQs about Home Humidity Levels
Is 60% Humidity Good for a House?
A humidity level of 60% isn’t great, but it’s not horrible, either. The ideal indoor relative humidity range is between 30 and 50% RH. I advise my clients that 60% on occasion when it’s rainy or humid outside isn’t necessarily a cause for concern. Still, we intervene with a solution when this becomes a regular or extended occurrence.
Is 70% Humidity Too High for a House?
Yes, 70% indoor relative humidity is much too high. If your home remains in this range for an extended period, you’ll notice mold and mildew growth, an increase in indoor airborne allergens, and potentially severe health side effects.
What Humidity Level Does Mold Grow?
Assuming you keep your home’s temperature between 70 and 80 degrees Fahrenheit, mold growth becomes a concern when relative humidity exceeds 65% indoors. Growth is more rapid in warmer temperatures, but 65% RH should be the mark for concern.
At What Humidity Level Should I Use a Dehumidifier?
The ideal indoor relative humidity is between 30% and 50%, but this doesn’t mean you must rush out and buy a humidifier if you’re reading 51% at specific points of the year. I typically advise my clients that intervention is necessary when indoor RH levels exceed 60% for more than brief periods.
Should a Dehumidifier Run Constantly?
A properly sized and installed dehumidifier should not need to operate all day to reduce humidity to ideal levels. Average run times can vary by moisture removal capacity, location, and seasonal weather changes, but a good target is 12 hours per day. Basements with water intrusion issues may be an exception to this rule.
