Geothermal System Filters: How to Get Fresh, Clean Air Year-Round 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? To ensure the... Geothermal System Filters: How to Get Fresh, Clean Air Year-Round 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? To ensure the...