In summer, an unventilated attic in Middle Tennessee can reach temperatures of 150 degrees Fahrenheit or higher. That extreme heat radiates down into your living space, dramatically increasing your air conditioning load. It also degrades the seal strip on asphalt shingles — the adhesive bond that keeps shingles from lifting in the wind — which is why most shingle manufacturers require proper ventilation as a condition of their warranty. In winter, warm, moist air from the living space rises into the attic. Without ventilation to carry it out, it condenses on the underside of the roof deck, causing moisture damage, mold growth, and in cold stretches, the freeze-thaw cycle that creates ice dams at the eaves.