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Calculating VOCs: Not all Low-VOCs Are Considered Equal

Jennifer Wong, APCO Worldwide; Dave Selley and Jennifer Kempf, Dow Corning Building Materials Protection

Water is the number one enemy of any structure, especially those made from concrete, natural stone or masonry. Penetrating water repellents have been a mainstay of the protective coating and sealing market for years due to their ability to protect the aesthetic properties of structures and provide protection against the damaging effects of water.

Like most coatings, paints, and maintenance products, water repellents are expected to comply with increasingly stringent regulations of Volatile Organic Compounds (VOC), which are any volatile carbon compounds that engage in atmospheric photochemical reactions. The simplest example of a VOC would be a solvent or drying aid. Common examples include alcohols (such as IPA), mineral spirits, kerosene, toluene or xylene. The only compounds that have been exempt from regulations are those that have shown negligible photochemical reactivity, such as volatile methyl siloxanes, acetone, and tertiary butyl acetate.  Conflicts between application specifications that require higher VOC products and tightening regulation standards pose a challenge to the market.

For water repellents and other similar materials, VOCs will typically evaporate under normal use.  Penetrating silicon-based water repellents offer unique benefits that protect the aesthetic properties of building structures against some of the damaging effects of water, such as an increase in cracks or breakage and white efflorescence deposits that stain brick or concrete structures.

The degree of VOC content contained in substrates has long been a source of controversy.  Vapor pressure, evaporation rate, temperature, time, and other chemical or physical properties all factor into the calculation. The degree of dilution can also affect VOC levels. If a product is diluted with a non-exempt solvent, VOC content usually increases. However, situations can vary with the degree and amount of solvent used.

The South Coast Air Quality Management District (SCAQMD) in California implemented architectural coating Rule 113, which contains the most stringent VOC requirements in the United States. Guidance documents, also known as “Suggested Control Measures,” serve as “model rules” for other regions to follow.

According to the SCAQMD, industrial maintenance coating primers, waterproofing sealers and waterproofing concrete/masonry sealers manufactured after July 1, 2006, should have a VOC content below 100 g/L. SCAQMD Method 304, in conjunction with EPA Method 24, uses established principles and ASTM methods for determining the VOC content of a coating:

VOC (g/L) =
 wt. of volatile org. compounds (g) - wt. of water (g) - wt. of exempt compounds (g)
vol. of material (L) - vol. of water (L) - vol. of exempt compounds (L)

While there have been concerns over the accuracy of Method 24, improvements are constantly being made utilizing increasingly advanced technologies. Most recently, changes have been proposed based on the recognition that not all VOCs are equal in their contribution to ozone production.

These many variations contribute to the endless debate surrounding the effects and content levels of VOCs in building materials. For more information on specific regional requirements, contact your state department directly. It is only through greater education, government coordination, regulation standards organizations and immediate response to continuously changing conditions that more accurate measurement tools can be achieved.


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