The National Association of Home Builders released guidance on Chinese drywall remediation Wednesday in hopes of helping remediators, homebuilders and homeowners take care of the issue. The guidance was compiled by risk analytics firm Marsh Risk Consulting and Maryland-based Building Health Sciences after several months of scientific study. Both entities noted the guidance is only to be used in relation to single-family, detached homes and not for commercial properties. Defective Chinese drywall and the health problems associated with it have become a major issue in recent years. After Hurricane Katrina hit in 2005, many homes around the Gulf of Mexico were rebuilt using the Chinese material after a shortage in U.S.-produced drywall. As of Jan. 7, there were 3,770 incidents reported of defective drywall, according to the Consumer Product Safety Commission. Florida has the most with 2,137 cases, followed by Louisiana with 704 cases and Alabama with 215. The NAHB guidance lays out a basic structure and step-by-step framework for dealing with a home potentially infected with problematic drywall. The framework consists of three testing phases, each with a different purpose. The recommended method of testing is an air corrosivity test with a metal probe, according to Barbara Manis, chief medical officer for Building Health Sciences. This method measures the amount of corrosive substances commonly produced by defective drywall. A probe is the most cost effective and ease-of-use device for this type of testing, Manis said in a teleconference Wednesday afternoon. The first test calculates the baseline measurement, which is taken after a home has been inspected and classified at potentially hazardous. It must be performed prior to any drywall removal. Following the initial baseline measurement of toxic drywall, a homebuilder or remediator must prepare for deconstruction of the defective property areas by fully documenting the infected drywall, putting all personal property items into storage and putting their plan in writing. The NAHB advised its members to remove and replace all low-voltage, signal or data wiring, replace switches and receptacles, as well as smoke, fire and carbon monoxide alarms as preparation for the deconstruction process. Lighting fixtures should be inspected for evidence of corrosion, the guidance states, however this hardware can usually be reused after deconstruction. Builders are advised to remove and replace the coils in all air-handling units and all duct work and sheet metal in the property. All low-voltage signal wire to HVAC controls should also be replaced, the NAHB said. Actual deconstruction is accomplished in two ways as defined by the NAHB guidance: total and selective. Total remediation refers to removing all drywall products and building systems, including cabinetry, carpeting and plumbing fixtures among many other items. Selective drywall usually refers to old homes that have been remodeled and updated with defective drywall. “We’re not talking about one panel in a room that’s next to another non-problematic piece of drywall,” commented Katherine Cahill, global product risk practice leader at Marsh Risk Consulting. She was also on the conference call. The NAHB also released strict guidelines on cleaning a property after the defective drywall has been removed. All building materials must be removed and the floor swept thoroughly. The home should be vacuumed with high efficiency particulate air  filters and afterward blown by large volume fans with HEPA filters, NAHB said. Then a homebuilder is required to use compressed air to “blow down” all surface areas and then air-out the house for at least 14 days. “I cannot emphasize enough, for all those conducting the remediation process, how important this step is,” Cahill said. It’s at this point the remediator does the second test called a clearance measurement. This test ensures no toxic material is left in the home. If the test comes back with an indication of airborne drywall substances still in the home, the cleaning and airing-out processes must be performed again before initiating the rebuild of the property, according to the guidance. If the clearance measurement indicates no toxic substances, a builder may proceed to build back the rest of the property. He or she performs a third test, known as a re-occupancy measurement, that tests the level of toxic substance in the air after the walls have been built back. This measurement verifies the elimination of defective drywall by associated various airborne compounds. To see a copy of the guidance in its complete form, click here. Write to Christine Ricciardi. Follow her on Twitter @HWnewbieCR.