I live in a ranch style home in a shore town 300' from the atlantic. The house is on a crawl space that is dry. I have a propane gas, forced air, heat & air unit. In the summer the air is usually on so the indoor humidity is OK. But in the winter with the heat set @ 70 during the day & 50 @ night {gotta save propane @ $3.50 a gal.} even with the central humidifier off, the humidity is always between 65 & 70%. The house always has a mildew smell. Is there anything that can be done to get the humidity down to 40-50%

First of all cover the crawl space with a layer of plastic. It does not make a difference how dry it looks or is it will still allow moisture into your home. If still to humid invest in a free standing dehumidfier. They work well in situations like yours and most can be connected to a hose for drainage so you no longer have to remember to drain the bucket.

I use a dehimidifier in my home in the winter and this removes a lot of water. Also be sure to use the bathroom vent fan when you take a shower or bath and let it run at least 10 minutes after taking a shower. This can help. Also the propane will actually be helping make your place humid. In the summer the a/c keeps the humidity under control. Do cover up the exposed ground in the crawl space as that will help also.