A common defect found during a home inspection is missing or deteriorated sealant at exterior penetrations. Exterior penetrations extend through the outer wall system and the air and water-resistant barrier, which creates a passageway for moisture-laden air. Windows, vertical trim boards, lighting fixtures, electrical outlets, outdoor condenser lines, electrical panels, and plumbing pipes are common areas that need additional sealant.
The primary reason that we advocate sealing these penetrations in a hot and humid climate is to prevent air infiltration. When we have a passageway from the exterior side of the home, directly into the interior, and factoring in the pressure differential between the two, these open passageways allow moisture-laden air direct access into the home.
The goal should be to limit the amount of moisture that is driven into your home while simultaneously removing the indoor humidity via your mechanical systems (Note that the direction of moisture travel in this environment is from the exterior to the interior). This interaction reduces the indoor air quality and the thermal comfort within the home.
Another reason it is recommended to seal these penetrations is to prevent rainwater from gaining access to any of the electrical connections. Over time, the exposure to moisture can weaken electrical bonds and increase the wear on components, which are both negatives for electrical safety.
Finally, a simple reason to seal these areas is aesthetics. When you eliminate gaps and openings in the exterior wall system, the overall appearance is improved. Couple that with color matching, or paintable sealant and you can further enhance the look of your home.
If you are looking for additional information on what type’s of sealants should be used, this Fine Homebuilding article sums up the particulars on caulks and sealants quite nicely.