Being comfortable and safe in our own home is paramount. One of the most crucial aspects of that safety and comfort is the humidity (the amount of water vapor in the air) inside your home. While most people think of the stuffy, heavy feeling of high humidity (especially when combined with high temperatures), low humidity can be just as damaging to your comfort, health, and property.
Ideally, your home should have an indoor relative humidity (RH) level between 30 and 60 percent. Above that range will not only make the interior of your house uncomfortable, but can cause mold to grow, with a negative health impact, encourage pests, and potentially damage wood and other materials. Low humidity can cause nosebleeds, sore throats, dry skin, and exacerbate asthma and other respiratory illnesses.
If you are concerned about the humidity in your, here’s how to measure it.
Three ways to measure humidity in your house
You can’t always rely on the “feel” of the air when it comes to relative humidity; higher dew points can make high humidity feel less uncomfortable, so it’s best to measure the humidity to determine if you need to install a dehumidifier or find other ways to lower the relative humidity in the house. There are three ways you can measure humidity on your own.
1. The ice cube method
A very simple method to determine whether your humidity is high or low requires nothing more than a glass of water and some ice cubes. This won’t be a very informative test, but it can broadly determine whether your relative humidity is high or low.
- Put three or four ice cubes inside a glass of water
- Place the glass in the room you want to measure and leave the room
- After four minutes have passed, check to see if there is condensation on the outside of the glass
- If there is, the humidity is high. If there’s no condensation, then your humidity is on the lower side.
Measuring the humidity levels in wet areas like kitchens and bathrooms can be challenging because the humidity will naturally spike (like when you’re taking a shower) and then drop.
2. The wet/dry bulb method
Another easy DIY method of measuring the humidity in your home is a bit of a science project called the Wet/Dry Bulb Method.
You’ll need:
- Two standard thermometers
- A piece of gauze or cloth
- A small fan
- Wrap the bulb of one thermometer in gauze or cloth
- Wet the cloth
- Arrange both thermometers so the fan can blow air over their bulbs
- Measure the temperature they report:
– The dry thermometer should remain stable
– The wet thermometer will show lower temperatures over time as the water evaporates - When the temperature of the wet thermometer stops changing, note both temperatures
- Subtract the dry reading from the wet reading
- Use the chart here or the calculator here to determine the relative humidity
3. Use a hygrometer
The easiest way to measure the humidity in your home is to purchase a digital tool called a hygrometer. You can buy devices with built-in hygrometers for less than $10, or buy more sophisticated smart devices.
Using a hygrometer to measure humidity is very simple: Set up the device according to instructions and note the result displayed on the device’s screen.
While most hygrometers are relatively accurate, it’s best to test and calibrate a new unit before relying on its results.
- Fill a bowl about 2/3 of the way with water
- Add salt and stir until no more salt dissolves; there should be a small amount of undissolved salt at the bottom
- Place bowl and hygrometer in a plastic bag together and seal the bag
- Wait six hours and read the hygrometer:
– If the RH reading on the hygrometer is about 75%, it is accurate.
– If the reading is higher or lower, the difference is your calibration factor.
For example, if it reads 70%, you should add 5% to all future readings
What to do if your house is too humid
If your home is consistently measured to have relative humidity over 60% you should act to reduce the humidity before it negatively affects your health or your property. Here’s what to do and not do.
What to do
What not to do
What to do if your house is too dry
If your home’s humidity levels are below 30%, take steps to bring it up to more comfortable levels. Here’s what to do, and what not to do.
What to do
What not to do
Wrapping up
The relative humidity inside your home can have a negative impact on your health, your enjoyment of the home, and the property itself. Taking steps to measure, monitor, and manage the humidity in your home requires a few simple tools and some easy lifestyle adjustments—adjustments that will pay off with a more comfortable and healthier home.
SOURCES
- Brook, DM. (2008). Home moisture problems. Oregonstate.edu
- The Editors of Encyclopedia Britannica. (2023). hygrometer. britannica.com
- Environmental Protection Agency. (2023). Mold Course Chapter 2. epa.gov
- Environmental Protection Agency. (2023). Mold and Health. epa.gov
- Hamer, A. (2019). Here’s Why Static Shock is Worse in Winter. discovery.com
- Healthline. (2020). 8 ways Dry Air Can Affect Your Health. healthline.com
- Institute of Measurement and Control. (1996). A Guide to the Measurement of Humidity. npl.co.uk
- Jimenez, IG. (2023). What Plants Humidify The Air: Learn About Houseplants That Increase Humidity. gardeningknowhow.com
- National Weather Service. Dew Point vs Humidity. weather.gov
- RLC Engineering. Determining Relative Humidity. Rlcengineering.com
- Team Homeserve. (2021). High Humidity Can Harm Your Home. Here’s How to Head Off Damage. homeserve.com
- World Health Organization. (2009). WHO Guidelines for Indoor Air Quality: Chapter 3, Moisture control and ventilation. ncbi.nlm.nih.gov
