Wood Floor Finishes
The Lowdown on Low VOC Finishes
An increasing amount of information is available to the public on air quality issues, including the possible negative effects of off-gassing of volatile chemicals. Indoor air quality has become important to many designers and specifiers, including those that specify wood flooring.
In construction, the maximum concentration of VOCs (volatile organic compounds) is often specified by LEED, the U.S. Green Building Council, and many other federal and state/provincial authorities. The maximum allowable limits for VOC emissions include all the materials that can give off VOCs including paints, carpets, millwork, etc., and may limit the type of finish that can be used on the floors so that it fits within the specified limits.
VOCs are emitted as gases from certain solids or liquids such as paints, varnishes, cleaning agents, cosmetics, degreasers, and hobby products. If the end-user has chosen safe indoor air quality as a priority, it is important to educate them about other potentially harmful products that they may be using already, and perhaps suggest more favorable options.
Traditionally, the most popular finishes used in floor finishing contained VOC content as high as 750g/L. Government regulations have required manufacturers of finishes to change formulations to become more VOC-compliant over the last few years. These regulations vary from state-to-state and can be as high as 550g/L and as low as 275g/L. In order to achieve compliance, many manufacturers have had to substitute different components than what was traditionally used. The effect has been that finishes have become more expensive to produce and, in some cases, the ease of application has been compromised.
Choosing a finish becomes a real balancing act with many factors to consider. Typically, the end-user’s main concerns are appearance, longevity, maintenance, and air quality. There are many types of finishes that may be beneficial in some respect and a hindrance in others.
Conversion varnish, a film-forming finish that is durable and easily maintained, offers incredible clarity and enhances the color of the floor. Conversion varnish and varnish finishes fall within their own category for VOC regulations in most states. VOC levels may fall within the limit of 725g/L. VOC restrictions have limited the use of these finishes in some parts of the U.S.
Moisture-cured urethanes are usually applied in commercial settings such as roller rinks and gymnasiums. They offer excellent clarity and depth, are extremely durable, and easily maintained. The solvents used in this type of finish are dangerous and require adequate ventilation, the use of a respirator, and other safety precautions. This finish falls
within the wood coating category and may have levels around 550-700g/L.
Although conversion varnishes and moisture-cured urethanes are higher in VOCs at the time of application, an argument can be made that, due to their durability, this type of floor finish will not require refinishing as often as other types of finish.
Oil-modified polyurethane (OMU) is one of the most widely used finishes. This type of finish is amber in color and forms a thick film build that enhances the depth and color of the flooring. It will continue to amber out from the effects of oxidation and UV rays, so the floor will take on a yellowish cast as the floor ages. OMUs historically have been the most popular finishes that flooring contractors have used due to ease of application, flow, and leveling properties. For these reasons, contractors that have been using OMUs for a long time may be reluctant to use other types of finishes. Floor finish manufacturers recognize that many contractors prefer to use this type of finish, so have had to constantly tweak their formulations to comply with the VOC laws that vary from state to state. VOC regulations have limited use of some of these finishes in some parts of the U.S. VOC levels vary from
>275 up to 550 g/L within this product category.
Waterborne urethanes are very common finishes used in our trade. The reason for their popularity is largely due to using water as a carrier instead of solvents, so their VOC levels are inherently lower. Their appearance is similar to the finishes already discussed, and
they don’t amber out to the same degree. Some of the waterborne finishes have been limited to use in some parts of the U.S. due to VOC regulations. VOC levels vary from 0 to 450 g/L within this product category.
Natural oils and hardwax oils have seen a real increase in popularity. Many of these products state that they contain 0 g/L VOCs. Natural oils and hardwax oils use oils such as linseed or vegetable oils. These finishes have a distinct appearance that suits wide plank rustic flooring, which has become a very popular look. These finishes have a very low luster look that brings out the natural character of the wood but offers little to no sheen. This type of finish does not have a visible film and protects the surface of the flooring by bonding itself to the wood fiber. VOC levels can vary depending on the product and manufacturer.
There are a number of factors that contractors and end-users must consider before choosing any finish. The trick is to educate everyone involved as to what options are available in order to achieve the best balance between the look the end-user wants, the suitability of the finish to their lifestyle, and the impact on indoor air quality.
Kjell Nymark is Technical Advisor at the National Wood Flooring Association in St. Louis. He can be reached at firstname.lastname@example.org.