It is summer and the basement is moist. You may not see any water, but if you can smell it and feel it, it is there. You may have a basement water proofing system in place, or perhaps you don’t have water seeping in your foundation from pipes or floor cracks. That’s the good news. The bad is that, this doesn’t necessarily mean that your basement is dry.
Often water enters a basement through capillary action, which wicks moisture through walls and floors. The floor and walls may not leak, but it feels damp to the touch because it wicks the water in to the surface. Water vapor also slowly seeps in through the concrete and raises the humidity. Basements act as chimneys pulling the outside air in the house and letting it out on the upper floors.
Humidity increases and condensation results as the hot outside air meets the cool basement. Even without condensation basements tend to have high humidity levels and mold grows rapidly, generating that musty basement odor. Dust mites love that high humidity too.
There are only two possible ways to eliminate condensation: heat the air or pull the moisture out of it. Obviously heating your basement to match the outside temperature is counterproductive, so the only real option is to dehumidify.