From Ground to Air: How Filters Protect the Power of Your Geothermal System A geothermal system uses a high-quality filter to keep your home feeling comfortable during hot summers and cooler winters. However, every homeowner needs to be aware of how these filters work and when replacements are due. Why?... From Ground to Air: How Filters Protect the Power of Your Geothermal System A geothermal system uses a high-quality filter to keep your home feeling comfortable during hot summers and cooler winters. However, every homeowner needs to be aware of how these filters work and when replacements are due. Why?...