Site grading and drainage plays a huge role in indoor air quality. If surface water is directed towards or trapped against the foundation wall, moisture may enter the basement or crawlspace. This moisture will raise the relative humidity of the home, encouraging mold growth. To keep surface water from entering the home, the homeowner or building manager should take a number of actions. These include the installation of gutters (provided they are well-maintained and that the downspouts discharge at least six feet from the foundation wall), re-grading the soil near the foundation to ensure the proper slope to direct water away, and eliminating swales or gullies that carry water towards the home. Accumulations of mulch or organic debris against the foundation walls or on the roof (pine needles, leaves, etc.) that might trap and hold moisture should also be eliminated.