Exposure to elevated levels of lead can cause permanent mental handicaps and psychological disorders in children, as well as hypertension and other maladies in adults. The potential for lead poisoning exists in much, if not most, of the housing that was built before 1978. Studies indicate that in some urban communities with older housing stocks, more than 35% of the children tested had elevated blood lead levels; and nationwide, nearly 22% of black, non-Hispanic children aged one to five living in housing built before 1946 had elevated blood lead levels.

Older housing stock contaminated with lead paint frequently includes multifamily units located in structures with uninsulated masonry walls. These structures often include two- and three-story walk-up apartments, larger apartment complexes, and public housing (both high-rises and townhouses). A history of heavy use coupled with moisture condensation on the exterior walls causes paint on many of these walls to deteriorate to the point that lead can freely enter the living space.

Looking for a low-cost solution, the Advanced Housing Technology Program at Oak Ridge National Laboratory (ORNL) and the Existing Buildings Efficiency Research Program at Argonne National Laboratory (ANL) jointly developed a composite wall system that not only encases the lead paint on wall surfaces but also adds a tight, well-insulated, and durable interior surface to perimeter walls.

Wall System Materials

The development team chose Louisiana-Pacific Fiberbond, 1/2-inch cellulose fiber-reinforced gypsum wallboard, for its structural characteristics, impact resistance, and surface durability. Its structural characteristics permit Fiberbond to be hung from the top nailer of the system, which results in a straight, true wall.

Celotex Tuff-R accompanies the Fiberbond as the rigid foam insulation. Tuff-R, a foil-faced, polyisocyanurate insulation, provides the highest available R-value within the limited thickness of 1 1/2 inches dictated by horizontal 2-inch x 2-inch nailers. EnerFoam, an easy-to-apply, quick-setting adhesive, bonds the insulation and wallboard together. The adhesive is a one-component polyurethane foam with limited expansion potential; no solvents are used that could destroy the rigid insulation. The research team selected each of these materials because it has properties that work well in the heavy-use environment of public housing.

Wall System Construction

As a general rule, builders construct the wall out of 1 1/2-inch Tuff-R insulation and 1/2-inch Fiberbond. The system, installed on the inside face of exterior masonry walls, uses no vertical studs or nailers and extends inward only 2 inches from the original wall (Figure 1). Other retrofit insulation systems, like conventional stud walls, consume 4 or more inches of living space.

Installers mechanically attach two nominal 2-inch x 2-inch wood nailers horizontally to the original wall, at the floor and at the ceiling. The nailers are sealed at the wall and at the floor or ceiling with caulk or foam adhesive. Sealing prevents lead-contaminated dust from migrating into the living space from under or around the nailers.

The installers trim a 4-ft x 8-ft sheet of rigid foam insulation to fit between the nailers against the original wall. They then attach the insulation to the original wall with the foam adhesive, applying the adhesive in 1/4-inch beads about 12 inches apart. Metallic tape at the seams of the insulation provides a continuous air and vapor barrier and helps contain lead dust particles.

Next, installers attach the Fiberbond. For best results, they first apply foam adhesive to the exposed surface of the rigid insulation in 1/4-inch beads about 12 inches apart. Then they place two 1/4-inch thick shims on the floor in front of the bottom nailer. The installers set the 4-ft x 8-ft sheet of Fiberbond onto the shims, offsetting the edge of the Fiberbond from the edge of the insulation by 6 to 12 inches so the seams will not align. This step strengthens the joint in the Fiberbond, reduces the potential for air and moisture to move into the wall system, and provides an additional barrier to contain lead dust. Six to eight drywall screws mechanically attach the Fiberbond to the top nailer while the wall board is being pressed into the adhesive. When the installers finally remove the shims, the weight of the Fiberbond sheet causes it to straighten out. The bottom is then attached to the lower nailer with three to four drywall screws.

The joints of the Fiberbond and drywall screws can be finished with standard tapes and drywall compounds. Standard painting or wallpapering techniques, along with the installation of a wooden baseboard or vinyl base cove, complete the installation.

Figure 1. Elements of composite wall construction. (Foam adhesive is used between the gypsum board and the insulation.)

System Costs

Contractor estimates vary depending on the cost of labor (geographic and union/nonunion variations) and the complexity of the actual project (windows, doors, outlets, pipes, and so forth). The Chicago installation, including base cover and painting, was estimated to cost $4.20 to $4.90 per ft² (1997 wages), based on professional crafts installation. Given the simplicity of the system, resident labor crews have the competency to install it in public housing developments. The use of semiskilled or nonskilled workers would significantly reduce labor costs while providing job experience for public housing residents.

Source: Heather Hastings, John Knox, and Helen Binns, Residential Lead Hazard Reduction: The West Town Lead Project. (Chicago: 1997 Affordable Comfort Conference, April 1997).
 
 

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