Attic insulation is a smart investment. It conserves energy by trapping heat in the winter, thereby saving your furnace from excess wear and tear. When adding new insulation, however, don’t make the mistake of blocking your home’s soffit vents. These vents are vital for maintaining the flow of fresh air in the attic. If you’re adding batts, cut them to fit around, not over, soffit vents. If you’re blowing in attic insulation, cover the soffit vents with a piece of batt insulation or a board, and remove the cover after the blown-in insulation settles.