What Should the Relative Humidity Be in a Basement?

by Charlie
What Should the Relative Humidity Be in a Basement

Do you think of basements as wet, uncomfortable places? Do you shudder at the thought of stepping down into yours, because you know it will feel damp and cold? Do you find you can’t store things in there because they get soggy and spoiled unless you seal them in plastic boxes? That’s a sure sign that something isn’t right.

Although basements often do have issues with moisture and humidity, they shouldn’t. A well-designed and well-maintained basement will not have any major humidity problems, and if yours does, you need to take action to solve it because significant humidity will affect both your home and possibly your health.

What should the relative humidity be in a basement? A basement’s relative humidity should be between 30 and 50 percent throughout the year. It may increase during some seasons and decrease during others, but it should generally be between these ranges. You may wish to get a hygrometer to measure the humidity in your basement, and then take action if it is too low or too high.

How Humid Should Your Basement Be?

Your basement should not be over 50 percent or under 30 percent humidity. Too much or too little humidity indicates that there is a problem that needs to be resolved, and keeping an eye on this will help you to catch problems before they occur. If the humidity increases above 50 percent, you will start encountering issues with mold.

Dampness can cause a whole host of issues. It will prevent your insulation from working properly, and may cause it to degrade and start to rot. It will affect things like paintwork and wallpaper, as well as many kinds of flooring. It will destroy woodwork, compromising your timbers and potentially affecting your home’s structural integrity.

Excessive humidity in your basement can spread to the rest of your home, and may have similar effects there. It creates a breeding ground for mold, which will affect your health and can cause breathing difficulties if you breathe it in. Additionally, moisture in your basement will damage items you have stored there, and will make the room cold and uncomfortable.

Dampness below your house will stop your house from feeling warm and dry, and can cause plenty of issues upstairs as well as downstairs.

Most basements are too damp, rather than too dry, but very low humidity can be a problem too. Low humidity can increase the risk of dry rot forming in your timbers, and may make the space more hospitable to pests and insects. Low humidity can make your skin dry and make exacerbate problems like nosebleeds and dandruff.

Furthermore, low humidity can also contribute to deterioration in your household decor, and may result in things like peeling paint. Overall, therefore, both conditions need to be avoided, and you need to keep your basement reasonably dry, but not arid.

It is worth noting that you might notice lower humidity levels in winter, especially if it is freezing. Levels could drop as low as 20 percent without causing problems, as long as this is a short-term reduction.

How Do You Reduce Humidity in Your Basement?

High humidity levels are generally a big problem in basements, but there are lots of things you can do to tackle them. First, you should find the source of humidity. Has a moisture barrier been compromised? Do you need more damp-proofing? Is there too much groundwater around the basement?

It may be expensive to fix some of these problems, but they will be key to getting rid of excess humidity in your basement. You should therefore deal with them as soon as you are able to.

In other cases, humidity might be caused by poor conditions. For example, if you turn the heat off in your basement during the winter, it’s likely to become damp, because cool air tends to be wetter. It might seem wasteful to have your heating on if you aren’t using the basement, but it’s key to keeping it reasonably dry.

Heating your basement will also help to keep your home warm, since heat rises, so it’s best to keep the room between 55 and 60 degrees F during the winter.

You should make efforts to increase the airflow in the room, too. Removing carpeting and making sure that the room isn’t too crammed with stuff may reduce dampness. Check whether things like washing machines are draining properly, and consider drying laundry in another room if necessary.

You can also reduce humidity by running a dehumidifier. This is a great solution if you have temporary sources of moisture (such as drying clothes) and the basement is otherwise dry enough, but if you think there are serious issues with the basement being damp, find permanent solutions before you turn to a dehumidifier.

Remember that summer air can be humid. If warm air flows into your basement, it will condense in the cooler space, leaving moisture droplets on the stone and metal in the room. Keep your basement windows closed on humid summer days to avoid this.

If you are really struggling with dampness in a basement, consider getting a company in to inspect the space and determine what’s wrong. This is better than struggling with dampness in the long term.

How Do You Increase Humidity in Your Basement?

If your basement is too dry, you should again investigate the cause. A broken AC unit or heating unit may be at fault, and will need to be addressed quickly. It’s rare for a basement to be too dry in normal conditions, so avoid using a humidifier, and instead find the cause and deal with it as soon as you can.

You will probably never need to increase the humidity in your basement, but use excessive dryness as a warning sign to investigate.

Final Thoughts

Relative humidity in your basement should usually be between 30 and 50 percent. Most basements suffer from excessive moisture, not dryness, but keep an eye on both scenarios to ensure your home stays comfortable and safe for you to live in. Deal with temperature fluctuations as quickly as you can to prevent damage and insect infestations.

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