The old saying “it’s not the heat, it’s the humidity” has a lot of truth to it. In recent weeks, many people — from Olympians to those living under the heat dome — have had to deal with a lot of heat and humidity combined.

Fortunately, humidity is not entirely out of our control.

The most comfortable home is one that’s balanced in a variety of elements. Humidity can upset that delicate balance by being too low or too high. A humidity level of about 45% is ideal. You don’t want it higher than 50% or lower than 30%.

High humidity tends to be a big problem in newer homes. Recently built homes have a tightly sealed interior envelope, which tends to keep the humidity inside. If it causes condensation, you’ll get moisture buildup around the house, including behind walls and ceilings. Too much humidity promotes the growth of fungus and mold.

Low humidity, on the other hand, can cause cracks in wood floors and damage electrical equipment. You can develop dry skin and susceptibility to cold and flu germs.

A quick way to check your humidity level is by using a hygrometer. You can purchase a basic model for less than $20 at many hardware and big-box stores. Make sure you take readings in different rooms; the humidity will vary around your house.

If you find that your humidity level is below 25%, consider purchasing a humidifier. Most options cost less than $75 and can effectively boost the humidity in a room by evaporating water and pumping it into the air. Or choose a more low-tech method by placing shallow dishes of water around the house, particularly near vents and sunny windows. As water evaporates, it adds moisture to the air.

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Dehumidifying a house is a more complex operation, since you must mechanically remove moisture from the air and direct it elsewhere.

There are a number of DIY options that minimize humidity that you can try before you bring machines into the equation. For instance, opening windows, leaving doors open throughout the house, increasing ventilation and using exhaust fans can bring down humidity levels. (Pro tip: Make sure your dryer vent directs air outside and has no leaks. Accidental heat loss from dryer vents is a big cause of humidity.)

If you prefer a more reliable solution, you can purchase a single-room dehumidifiers. A unit for a very small room will cost about $50; systems for larger rooms start at around $175. This is a relatively efficient approach, though you’ll have to regularly dump water out of the collection chambers.

For a permanent solution to excess humidity, consider installing a whole-house dehumidifier. This attaches to your home’s HVAC system and removes moisture from the air as it cycles through the returns. These don’t come cheap; expect to pay between $3,000 and $5,000 for a unit. Be sure to hire a licensed HVAC installer who is experienced with these kinds of systems.