Vapor Barrier
A vapor barrier is a moisture-impermeable material installed in building assemblies to prevent water vapor from penetrating walls, floors, or ceilings and condensing within insulation or structural components.
Vapor barriers (technically called vapor retarders) control moisture movement through building assemblies, preventing water vapor from migrating from warm, humid areas to cold surfaces where it condenses. In heating climates like Denver, vapor barriers typically go on the warm side of insulation—on the interior of exterior walls—to prevent warm, moist indoor air from reaching cold exterior sheathing where condensation would cause rot and mold.
Why It Matters for Denver Homes
Denver's cold winters and heating season create the classic conditions for condensation problems. Warm indoor air carries moisture that wants to migrate outward through walls. When this moisture reaches cold surfaces, it condenses into liquid water, potentially rotting wall cavities from the inside out. Common vapor barrier materials include 6-mil polyethylene sheeting, kraft paper facing on fiberglass batts, and foil-faced rigid insulation. Proper installation with sealed seams and penetrations is critical—a poorly installed vapor barrier can trap moisture rather than prevent it.
Common Applications
- Exterior wall cavities: Polyethylene sheeting on interior side before drywall
- Crawl spaces: Heavy poly sheeting over ground to prevent ground moisture
- Basement walls: On warm side of insulation before finishing
- Under concrete slabs: Preventing ground moisture from wicking up
- Ceiling assemblies: In cathedral ceilings and flat roof applications
Related Terms
R-Value
R-Value measures the thermal resistance of insulation materials, with higher values indicating better insulating properties and greater energy efficiency.
Rigid Foam Insulation
Rigid foam insulation consists of stiff panels of polystyrene, polyisocyanurate, or polyurethane foam that provide superior insulating value and moisture resistance for walls, roofs, and foundations.
Waterproofing
Waterproofing involves installing membranes, sealants, and drainage systems to prevent water from penetrating foundations, basements, showers, and other vulnerable areas.