If you live in a particularly humid climate, or have small living spaces with limited ventilation such as a crawlspace, a good dehumidifier can make your home less hospitable to allergens like dustmites, mold, and mildew by reducing humidity levels. Dehumidifiers also reduce irritation to your skin and respiratory system, allowing you to breathe easier; help to protect structural integrity; and save energy.
Health protection. When you improve the air quality in your home by using a dehumidifier in your crawl space or basement, you're helping to protect your health. If your home experiences relatively high humidity, it becomes a petri dish for dust mites and mold. By using a dehumidifier in your crawl space, you are decreasing the moisture in the air and improving air quality. Improving indoor air quality through moisture control can reduce and perhaps even prevent some symptoms of allergies, including eye irritation, headaches, and respiratory issues.
Pest protection. If you can control the moisture in your encapsulated crawl space by using a dehumidifier, you're not only protecting your health, but you're also protecting against pests. Controlling the moisture in the air reduces the chances of pest infestations, which are believed to cause more damage to homes than storms and fires combined
Increase structural integrity. If the relative humidity levels in your crawl space exceed 70%, it is most likely will produce condensation, which increases the likelihood of wood rot. Wood rot is likely when the moisture content in the air is at least 28%, and it happens when liquid water touches the wood. If the wood in your crawl space becomes damaged, there's a possibility that the wood will no longer be able to hold the weight of your home. A dehumidifier in your crawl space will help to protect your home from this moisture-induced wood rot.
Living space comfort. High levels of humidity can affect your home's comfort levels by making you and your household members feel hot and sticky. If you decrease the temperature of the air conditioning unit to remove the humidity, you wind up becoming cold and clammy. If you install a dehumidifier in your crawl space, you can more easily control the humidity levels in your home to ensure that you and your family are always comfortable. What's more is that by using a dehumidifier in your crawl space, you'll feel more comfortable at a higher temperature, which helps save money on energy.
Efficient Use of Energy. If your instinct is to turn on your air conditioner to remove excess humidity in your home, you'll unfortunately wind up causing your energy bill to go up - because more air means more energy. If you use a dehumidifier in your crawl space, instead of turning up your air conditioner, you can maintain relative humidity levels at or below the recommended 60% during springtime, summertime, and the fall.
https://www.advantaclean.com/blog/2017/may/5-benefits-of-having-a-dehumidifier-in-your-craw/