Certain telltale signs indicate it's time to consider replacing heating and cooling equipment, or improving the performance of your overall system. It may be time to call a professional contractor to help you make a change if:
Consider replacing with ENERGY STAR qualified equipment that uses 20 percent less energy than new standard models.
Consider replacing with an ENERGY STAR qualified furnace, which is 15% more efficient than a conventional furnace. If you have a boiler, consider replacing with an ENERGY STAR qualified boiler that is 10% more efficient than a new, standard model.
Your cooling or heating equipment my have become less efficient.
This could be a result of poor ductwork design or if some rooms have lots of glass and a southern or western exposure zoning might be the solution.
Install an ENERGY STAR qualified programmable thermostat or have a good contractor install one and instruct you on its use — to start saving energy and money while they're away or sleeping.
In winter, most homes need to add moisture -- A whole house humidifier operating independently from the heating system will solve your "too dry in winter" problems. In summer your air conditioner removes moisture. However, in both summer and winter the moisture problem can be made worse by a leaky ductwork system.
Almost always the main source of dust comes from the rockwool and fiberglass dust particles found in the attic. Solution---remove all the blown-in insulation and replace with spray foam insulation. Leaky ducts can pull particles and air from attics, crawl spaces and basements and distribute them throughout your house. Sealing your ducts may be a solution.
You could have an undersized duct system.
Energy Star - U.S. Environmental Protection Agency - U.S. Department of Energy