Are squeaky floors driving you nuts? The culprit is what lies beneath, the foundation. Poor ventilation in the basement or foundation can lead to moisture problems. At best your house will have a musty odor which will turn to squeaks and eventually rotted floor framing.
Be sure a visual inspection of foundation is on your home maintenance calendar. Look for black or green spots that indicate mold. Note that white spots are typically salt deposits left from evaporating water. While these spots are not very damaging, cleaning them with a vinegar and water solution will give the foundation a better appearance. Use a wire brush and 10% solution of muriatic acid in water for stubborn spots. Take the necessary precautions while working with acids and avoid skin contact and use eye protection.
If these spots persistently reoccur seal the foundation with a silicone concrete and masonry sealer. Reoccuring spots also is a good indication of a moisture problem. Start investigating the problem by inspecting all the plumbing in the basement. Closely inspect all the pipe fittings, toilets, and tubs for leaks. Anything dealing with water above should be considered a suspect. Corroded pipes in older homes can be fixed with a sleeve.
Next check the outside drainage. Overwatering flower beds adjacent to the house can flood into the basement. Likewise, gutters and downspouts not directing water away from the house can have the same effect. To help elliviate any flooding around the perimeter inspect the soil grading to be sure it slopes away from the house. The slope should be visually evident.
The primary goal is to eliminate the problem but increasing ventilation also helps. Add a foundation vent or an exhaust fan. If these solutions don't help consider installing a moisture barrier or French Drain. It might also be time to call in an expert.