How to Measure Humidity in a House and What Is Ideal Humidity Level

Measuring humidity in a house. What is the ideal humidity level.

Have you noticed a stickiness and clamminess in the air at home? If your windows are foggy or you notice the smell of mildew or sight of mold, the humidity in your home may be too high. Discomfort and inconvenience are not the only problems associated with excessive humidity. Your allergies and asthma may get worse because of the growth of fungi, mold, and dust mites. For all these reasons and more, you should not settle for a house with excessive humidity. High humidity can be prevented and resolved by steps as simple as cracking a window.

What is Humidity?

When we talk about humidity, we’re referring to the amount of water vapor in the air. When there is a high level of water vapor, we say that humidity is also high. When we measure humidity, it’s usually described as a percentage. It’s expressed as a percentage of the most water vapor that the air can hold at any particular temperature.

If we say its 100% humidity, we mean that the air is as full of water vapor as it can possibly get, and it’s likely that it’s going to rain.  When humidity is low, it feels cooler to us because our sweat evaporates into the air. But when there’s a lot of water vapor in the air — so humidity is high — there is less room for evaporated sweat in the air, so it doesn’t evaporate from our skin easily. As a result, it feels hotter to us.

What’s the Ideal Humidity Indoors?

We often blame humidity for all kinds of things from fogged up windows to high temperatures to frizzy hair. Humidity is important, though. If humidity is too low, you’ll experience dry skin, irritated sinuses and throat, and even itchy eyes. But if it’s too high, humidity will cause dangerous bacteria to grow. Mold may trigger allergy symptoms and breathing problems, and make asthma worse than ever.

There’s a sweet spot for humidity inside your home, which always goes up and down depending on the time of year, weather, and the geography where you live. As a general rule, humidity is higher in summer and lower in winter. What’s the ideal humidity inside your home? The Mayo Clinic says that the ideal humidity in your home is between 30 and 50 percent.

How to Measure the Humidity in Your Home

Just like a thermometer measures temperature, you can measure the humidity inside your home using a hygrometer (sometimes referred to as a hydrostat though they aren’t the same thing). You can purchase hygrometers on Amazon for less than $20. Really, they’re just thermometers that measure humidity, too. But they can be useful.

A hydrostat is to humidity what a thermostat is to temperature. Just like a thermostat works with your HVAC system to control temperature, a hydrostat can work with your HVAC system to control humidity in your home.

Causes of High Humidity

Life causes humidity in our homes. Many of our regular daily activities produce water vapor, many more than you might realize. Before the advent of incredibly air-tight homes to reduce heating and cooling costs, that water vapor may have simply vented outside. Instead, as much as four gallons of water is produced daily just be activities of normal life — things like showers and baths, dishes and laundry, cooking, cleaning, and breathing.

Other sources of unwanted humidity that you might not think of are leaky pipes, house plants, and even firewood stashed by the fireplace.

How to Reduce Humidity? Yes, It Can Be as Simple as Opening Windows

For a potential problem that is so common but that can also be so serious, excess humidity in your home is also a problem that can easily be dealt with. There’s a wide range of possible solutions from the free to the very expensive. If you’re experiencing high humidity, try the simplest and easiest of these before jumping into the more expensive. But don’t tolerate excess humidity for too long. The health risks are too high to ignore.

  • Open a window – a well-sealed home is easy to heat and cool, but those seals also hold in water vapor. Opening a window will allow the circulation of air which will promote the venting of humidity. Oh, one thing. Don’t expect humidity levels to go down if you open the windows while it’s raining or snowing. Keep them closed then.
  • Keep the air moving with floor and ceiling fans
  • Cover fish tanks and aquariums
  • Make sure your attic vents are clear to allow moisture-laden warm air that rises into the attic to escape
  • Shorten your showers – steam is water vapor. The longer your showers, the more water vapor gets into your home. It’s as simple as that.
  • Use exhaust fans  – Use your bathroom exhaust fan and stove range when showering, bathing, and cooking. Be sure they’re properly installed and vented to the outside.
  • Don’t run half-empty washing machines and dishwashers – Both these machines put out water vapor, and there’s no point pretending you’ll stop using them. But wait until they’re full to avoid using them more often than you need to
  • Consider your plant population – If you’re seeing mold growth and you have roomfuls of plants, it’s not a coincidence. Reducing your plant population may eliminate the conditions for mold growth
  • When cooking, put lids on your pots – remember, steam is water vapor and water vapor is humidity
  • Line dry your clothes outside – Drying your clothes on a line may be good for the environment by saving electricity. But if you dry your clothes indoors, where do you think that water goes? Into the air.
  • Weatherproof around your windows or upgrade your windows – your windows or the surrounding structure may be allowing water vapor into your home
  • Look for and fix leaking pipes
  • Waterproof basement floors and walls especially if you’ve noticed water seeping from those surfaces

Dehumidifiers Can Help Reduce Humidity in Your Home

Those 13 suggestions will help prevent, reduce, and respond to high levels of humidity in your home. But they may not be a complete solution. If humidity continues to be an issue, consider using a dehumidifier.

Dehumidifiers can be portable, self-contained units moved from room to room (generally in a basement) or fully integrated into your HVAC system (your furnace and central air conditioning system).

Dehumidifiers — even stand-alone units — will pull moisture from the air, prevent breeding of bacteria, and reduce energy costs since dryer air is easier to heat.

When selecting a dehumidifier, measure your home since a standalone dehumidifier’s capacity is determined by the size of the space. A properly sized unit will run more efficiently and effectively. Also consider how the dehumidifier will drain. The moisture pulled from the air condenses into water. Many standalone units collect that water in a bucket that will need to be emptied. Once full, the dehumidifier will have an automatic shut off.

Some units will include hoses which can direct condensed water vapor into a drain.


Excess humidity in your home may seem like just a nuisance, but your comfort is not the only thing being compromised. Too much humidity for too long can damage your home, your belongings, and your health. There is an enormous range of possible solutions for excessive humidity — as simple as opening a window. You don’t need to — and shouldn’t — put up with excess humidity any longer.

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