Treating High Humidity in basement

The floor heat system may be the sticking point. An appropriately sized dehumidifier works fine in our house, but we have forced air heating/cooling. During the cold months, the forced air heat dries the air so that the dehumidifier is not even needed. I am not familiar with your floor heat system (assume it is hot water in pipes, but could be glycol in plastic tubes?), but the temperature differential between the heated room and the surrounding ground will contribute to a migration of water vapor into the room. If there is not an adequate vapor barrier below the slab, you could be bringing significant moisture from the ground into your basement area. Moisture vapor will also migrate through the walls if they are not damp-proofed. I believe the best place to start would be to purchase a good quality, moderately large dehumidifier and let it run for a week or so then see what you think. It sounds like you own a hygrometer, so you can measure the relatively humidity at incremental distances away from the dehumidifier to check the effective radius of treatment. Depending on your basement layout, you may need two dehumidifiers. The next step would be to install some form of forced air ventilation system, but before doing anything like that, I would consult an HVAC contractor. In fact, I would probably call a contractor as soon as I determined one dehumidifier alone was not going to work.

Hi Audioquest4life, I just thought of a question; since you have floor heat, is there any provision for return air. In houses with forced air heat, there are return air vents. When the forced air pressurizes the room, air flows out through the return air vents resulting in a circulation that I would assume lowers the ambient humidity. However, I am not familiar with how exactly the floor heat works, and what provisions are made for air circulation and humidity control. When you say you moved into a "new" house, is that a newly constructed house, or one that is new to you? If newly constructed, I would expect a modern system with some provision for humidity control, so you could contact the builder to discuss the issue. If it is an established house, but new to you, you should consider calling a residential HVAC contractor with a good reputation and see what they say. Let us know how it is going.