Closed Crawl Space Assemblies

For years common construction practices and building codes required that crawl spaces be ventilated to the outside to reduce moisture under a structure. Research indicates crawl spaces ventilated to the outdoors do not function as intended, allowing humid outdoor air to come into contact with cooler surfaces under a home to form condensation and to trap moisture.

Services Offered

Evergreen is a professionally trained installation contractor of closed crawl space systems that offer a code-accepted method of reducing moisture content and improving energy efficiency by eliminating and reducing air and vapor infiltration in the crawl space.

  • Damp Proofing involves the application of a minimum 6-mil plastic vapor retardant material to the inside of the foundation wall to help reduce and control moisture infiltration into the crawl space area.
  • Insulated Foundation Wall involves the installation of rigid foam board insulation using powder loaded nails and special plastic washers over the plastic vapor barrier on the inside of the foundation wall. According to code, foam board must provide R-10 insulation value to eliminate having to insulate the floor joists.
  • Closed Crawl Space Floors involves the application of minimum 8-mil plastic vapor barrier on the crawl space floor using sealing tape at each seam to seal out moisture from the ground. In new construction, Evergreen installs a temporary, sacrificial vapor barrier during construction which is replaced with a final, sealed layer of plastic once the structure is complete. This helps reduce potential effects of moisture on construction materials such as hardwood flooring and interior trim.

Benefits

  • Energy Efficient - Provides greater energy efficiency by helping to create a sealed envelope, limiting air and vapor infiltration in a home or building
  • Increased Comfort - Improves performance of a home or building’s HVAC system and reduces drafts
  • Reduced Moisture - Controls moisture, limiting condensation in a crawl space and the structure above it
  • Reduced HVAC - May result in lower HVAC loads and smaller HVAC system requirements
  • Inhibits Mold & Mildew - Maintains humidity levels at approximately 50%, inhibiting ability of mold and mildew to form or grow
  • Reduced Costs – Eliminates need to insulate floor joists or provide foundation vents, and helps reduce the costs of heating and cooling

Design Illustration

The following architectural detail illustrates a complete closed crawl space assembly:

Diagram: Closed Crawl Space
Source: Advanced Energy, Closed Crawl Spaces

Grading & Drainage

Evergreen installs closed crawl space assemblies that rely on the proper grading and drainage of a jobsite by an experienced grading contractor. Evergreen’s closed crawl space vapor barriers can be very effective at reducing moisture, but they are not designed to protect against storm water run-off, floods or other significant water inundation.