How is Chinese drywall different from other drywall?
All drywall contains sulfur. The primary component of drywall is calcium sulfate, or gypsum. This gypsum contains sulfur, but the sulfur typically remains in the solid form, and is non-volatile (does not vaporize into the air). Therefore, most drywall does not lead to the types of conditions associated with Chinese drywall. The Chinese drywall that is causing problems with corrosion and odor releases volatile sulfur components.
Several studies have been carried out on Chinese drywall, most notably by Unified Engineering on behalf of the Florida Department of Health and the US EPA Environmental Response team, as well as internal studies by WJE.
Chinese drywall has several differences from domestically produced drywall, in addition to the production of volatile sulfur-containing vapors. Chinese drywall contains greater amounts of strontium than domestic drywall. Strontium is an element similar to calcium, and can be found in varying degrees in natural gypsum deposits. The high strontium content in the Chinese drywall is indicative of the source of the drywall, and likely unrelated to the production of volatile sulfur components. Additionally, Chinese drywall has generally higher quantities of calcite and/or dolomite than other sources of drywall. Again, this is likely because of the source of the natural gypsum, as calcite and dolomite are often found with gypsum in natural deposits. Chinese drywall samples have also been identified as having higher organic content than other drywall materials.
The volatile sulfur compounds have been identified as hydrogen sulfide, carbonyl sulfide, carbon disulfide, and several organic sulfur-containing compounds. The Unified Engineering found higher levels of these compounds coming off a domestic sample than the Chinese samples, which they interpreted as an indication of cross-contamination.
Where has Chinese drywall been found?
The Florida Department of Health has reported cases of Chinese drywall in forty-four states, Puerto Rico, and American Samoa. The greatest number of cases has been reported in Florida and Louisiana. This geographic distribution is apparently due to two factors: 1) the high demand for building materials during the 2003-2007 building boom in the Southeast, and 2) hot and humid conditions, which have been shown to exacerbate emission of volatile sulfur-containing fumes. However, Chinese drywall has also been reported in western states including Wyoming, Washington, and Arizona.
Why does Chinese drywall release volatile sulfur components?
The reason that Chinese drywall emits volatile sulfur components has not been determined conclusively. Unified Engineering proposes the following possibilities in their report: treatment of the drywall with a biocide during the importation process, chemicals used in preparation of the facing paper, contaminants in the gypsum, components of the adhesive used to bond the drywall to the paper, or others. The EPA did not provide any potential causes for the vapors in their report.
WJE exposure tests have indicated that high humidity and high temperature accelerate the rate of emission of volatile, corrosive sulfur components being produced from the drywall, and therefore the rate of corrosion. Certain types of microorganisms, sulfate reducing bacteria, are known to decompose gypsum in certain conditions, including the presence of liquid water, moderate pH, moderately elevated temperature, and the presence of organic material. Also, sulfides (as opposed to sulfates) are known to decompose upon exposure to moisture. Other mechanisms may also be a factor in the production of volatile sulfur compounds, and are being investigated.
WJE studies of Chinese drywall
WJE scientists have analyzed Chinese drywall from multiple sources, and compared findings with several samples of domestically available drywall. WJE personnel have characterized the drywall samples by a wide variety of techniques, including: 1) x-ray diffraction, 2) atomic absorption spectroscopy, 3) ion chromatography, 4) Fourier transform infrared spectroscopy, 5) scanning electron microscopy with energy dispersive x-ray spectroscopy, 6) polarized light microscopy, 7) x-ray fluorescence, and others. These studies have been aimed at understanding the differences between Chinese and non-problematic drywall, as well as identifying “markers” or chemical or physical differences between Chinese and non-problematic drywall that can be used to identify the source of the drywall, both in the field and in the laboratory.
Additionally, WJE scientists have been conducting laboratory exposure and comparative studies to better understand the adverse effect of Chinese drywall on building materials. Studies related to vapor transmission and potential contamination of material surrounded by Chinese drywall are being conducted to determine the long term effects of vapors to interior finishes. In particular, this study concentrates on non-Chinese drywall and wall and roof insulation that may be contaminated by the problematic vapors, if exposed to volatile sulfur compounds from Chinese drywall for extended periods.
Chinese drywall solutions by WJE
WJE provides services to building owners, contractors, insurance companies, lenders, realtors, attorneys and others looking for scientifically-based solutions to Chinese drywall problems. Clients benefit from an interdisciplinary team of engineers, architects, and materials scientists who have developed advanced techniques for identification of Chinese drywall, as well as evaluation and mitigation of its effects.
- On-site nondestructive identification of Chinese drywall
- Laboratory analysis of drywall samples for Chinese drywall markers
- Evaluation of corrosion damage from Chinese drywall vapors
- Strategies for mitigation of Chinese drywall effects
- Litigation consulting and expert testimony