Optimizing my health

I am quite distraught with the cleanliness and integrity of the air quality in our home.  I have been researching different types of air quality accessories that are available to partner with our heating/cooling system.  There are so many options that I can’t decide which would be best. I live in an area with year round weather extremes. It is necessary to run either heating or cooling almost all the time.  To prevent energy waste, I’ve tightened up the house, sealed all cracks and made every effort to keep the heating/cooling bills as low as possible. Because of this, the same stale, contaminated air is trapped inside and continuously circulated.  Whenever the furnace or air conditioner starts up, it’s most likely spreading pollutants throughout the house. It’s possible that the inner workings of the equipment are contaminated with bacteria, mold and other harmful growth, which is then introduced into our family’s breathing air.  In the Winter season, with the furnace blasting heat non stop, the air in the lake house gets overly dry. A lack of humidity can cause mangle to lake house furnishings, chapped lips, headache, sore throat, bloody noses and a whole bunch of health complications. In the warm season, despite the air conditioner running, there are problems with humidity.  Excessive moisture encourages dust mites, mold, mildew and viruses, and can aggravate symptoms of dust sensitivity and asthma. I have been looking into a whole lake house solution, such as a humidifier, ventilator, dehumidifier, air cleaner or a germicidal UV lamp. Each of these air quality accessories serves a different however effective function. I wish I could afford to purchase all of them, and optimize the health and comfort of the home.