Hello,
My house is just over 4 years old and I have had problems balancing the air on the main level from the time I bought it. One room will be 8 degrees different from another. I also have an unfinished basement where I have had moister problems since I bought it. No leaks but a lot of humidity and mold even with running a dehumidifier. There are two cold air returns one upstairs and one on the main level. I just noticed in the basement the other day that the cold air return for the main level is not enclosed. You can get on a latter and look right in or look up and see the filter on the main level cold air return. The insulation around and above it are filthy with dust -- like what a dirty air filter looks like. Is this normal? What effect could this be happening with the main level balancing? What effect could this is having with the basement moister problem.

You are having the somewhat standard problems for a late model home. The care and consideration is not put in place when the home is built since more attention is placed on items that SHOW like kitchen cabinets and upgrade carpets. In other words the money was spent elsewhere instead of the HVAC system. In order to figure out the problems you will have to start back at the beginning and do what they DID NOT DUE that is causing all the problems. First you need to do or have done a Manual J and then also a Manual D. These items will set the correct size of the HVAC equipment and the correct size of the duct work. Once you find out all that info then you can calculate where the problems are and come to a conclusion as to how to make the repairs. NOTHING else you do will be a fix or a cure until you find the root of the problem. Doing the Manual D and J will go a long way in finding your problems. If you cannot do this yourself there should be a local company in your area that can help you out. It will cost some $$$ for all of this but you will be pleased with the results if done properly. One last note. Do not feel bad about your situation since most homes built in the past 50 years also have a problem unless extra attention was made on the HVAC system as part of the contract to build. To bad you did not figure this out during the first year of ownership since most builders honor a 1 year warranty for items like this.