If your home is under-insulated, adding more insulation can help you save money and improve comfort. However, once your home has the recommended insulation levels for your area, adding more is not only a possible waste of money, but it can actually be detrimental to your comfort and air quality. If your home is too airtight, pollutants like dust, pollen and cooking odors will linger, requiring an energy-wasting ventilation system to bring in fresh air. Additionally, moisture can collect in over-insulated homes, leading to mold issues. Going above the recommended insulation levels for your area is unnecessary and costly. In Southern California, that typically means no more than R-60 in the attic, R-21 in the walls and R-25 in floors or crawl spaces.