Benefits of Exterior Foundation Insulation
Homeowners and builders alike are viewing basements as valuable living space. Although, basements have been known for being cold and damp, playrooms, bedrooms, home theaters and work out areas are finding their way to the lower level. Exterior foundation insulation combined with a quality waterproofing membrane, addresses the problems associated with both moisture intrusion and energy loss commonly found in the basement.
There are several ways that water can enter into and through a basement wall. Exterior ground water can leak through wall cracks, defects, or the wall itself. Hydrostatic pressure on the wall can increase the likelihood and severity of these leaks. Condensation of moisture, from interior air on interior foundation wall surfaces, can create the appearance of a wall leak even though no leak exists. Finally, capillary action can also contribute to wall dampness and moisture problems. A quality waterproofing system with drainable exterior insulation such as Protecto-Coat XP is the most effective strategy to address these issues.
A system such as this prevents ground water and vapor from penetrating the foundation wall. Perhaps the greatest benefit of these systems is the drainage capabilities of the insulation. The boards drain at a rate that will prevent the build-up of hydrostatic pressure on the foundation. Due to the drainage ability, water retention in the board is far less than other exterior insulations. Essentially, a direct path has been created for water to flow to the perimeter drainage system. The waterproofing system further blocks water and vapor penetration.
The potential for condensation is greatly reduced due to the effect exterior insulation has on the inside wall temperature. Exterior insulation moves the dew point, or condensation temperature, away from the interior wall surface and toward the outside of the wall. The interior wall remains nearly the same temperature as the inside living space. Therefore, greatly reducing, if not eliminating condensation. In sharp contrast, interior insulation greatly increases the potential for condensation problems during winter conditions. Interior insulation significantly reduces the warming of the interior foundation wall surface by the heated basement air; the surface will often cool to well below the dew point in winter. This causes condensation on the wall surface with non-porous insulation, and/or within the insulation for porous insulations such as fiberglass. The use of interior blanket insulation, as well as interior stud framing insulated with fiberglass batts, produced problems associated with mildew, decay, and odors according to reports from Canada (Fugler, 2002) and Minnesota (Ellringer, 2002).
Any moisture introduced by capillary action from the base of the wall is more effectively managed with exterior insulation as well. Interior insulation requires a vapor retarder to reduce the total amount of water that can reach and condense on the interior wall surface. While this retarder is far less than totally effective in preventing moisture condensation on the foundation walls, it does significantly retard the dissipation of any moisture introduced by capillary action. With exterior insulation, the capillary water can evaporate to the interior without hindrance from an interior vapor retarder.
Building a safe, energy efficient home is a mark of an excellent builder or contractor. With the foundation protected by the combination of exterior, drainable insulation and waterproofing, homeowners can feel confident that they will enjoy lower utility and maintenance costs, as well as a healthy, comfortable living space.