Oh, i feel for you. Keeping the Humidity down has been a quest. In the newer tighter homes, one person not turning on the bath fan can increase your humidity. Humidity monitor will help, window sweating not a good indicator. I ended up running our ex-changer all winter long and having to use the bath fans to keep it in the 30%-35%, range never had the issue of it getting too dry. Once it warms up we run the ex-changer intermittently. We never had issues and didn't need the bath fans until the kids got older. We have a top of the line Venmar ex-changer, there are two types EVR and HVR and what type of ex-changer you use depends on where you live. We have an EVS dou, which allows us to exchange the air in the winter and the summer. I have never opened a window, all the air is filtered and exchanged, very little dust and no odors in the house. House before this one didn't deal with the window sweating issue and the windows rotted. Had to replace half the windows. Told myself I would never have that happen again. Also, new, new home with everything off gassing humidity is hard to control. If this is the first winter in the home and you do have an ex-changer and it is in fact running i wouldn't start to panic until next winter. Depending on your area it is code to have some form of ex-changer. Now some builders will cheat and use a scuttle. They do work, but they defeat the purpose of a new tight built home. Basically they run a hole in your cold air return to the outside with a damper in it. When you run your bath fan it creates a negative pressure and fresh air comes in through the opening to the outside.