Choosing Green Finish Materials: Paint
Paint serves both a decorative and a protective function as a building material. Wall color is one of the more frequent design changes made to the interior of existing homes. On exteriors, it can also preserve the surface and structure of a home, increasing its longevity. "Green" paint is low or zero VOC, water-based, without harmful preservatives, biocides or solvents.
Paints have a significant impact on indoor air qualilty as they dry and outgas. The VOC level is represented in grams per liter (gpl). For many years, the VOC level defined as "low" was 150 gpl or less. In recent years, the formulations of paints and stains have improved and the quality of paints have improved even as the VOC level has declined. There are several top-quality interior wall paints with zero VOC ratings.
VOC levels vary significantly by product type. Many stains and clear finishes still contain higher VOC levels. A good reference for reasonable VOC targets for a variety of paints and stains, as well as adhesives and sealants, is the Leadership in Energy and Environmental Design program.
If you choose a product with anything higher than zero VOCs, you must provide adequate ventilation and time for curing before the house is occupied. Don't forget the painters, who experience the most direct and lengthy exposure to paint fumes. If you're going to repaint an existing home, avoid paints that outgas as the VOCs will collect in the soft surfaces of the home (carpet, furniture, drapery) and return to the air. Inside a house, the larger the surface area covered with a VOC paint, the greater the impact. While using a low VOC paint on the exterior of a home may not affect the indoor air quality, it will contribute less to outdoor pollution. In fact, most VOC regulations currently target the impacts of VOCs in the outdoor air in pollution and photo-chemical smog.
Important considerations when choosing a paint:
- Durability - Many water-based paints are as durable as oil-based ones. Choosing a durable product means you won't have to repaint as often. It is also very important to follow the manufacturer's application instructions to achieve the proper results.
- Toxins - The VOC level of paint is shown on every container. Just look for the smallest type on the label! When researching products, you can often find the Material Safety Data Sheet (MSDS) on the Web. Avoid products containing formaldehyde, petroleum distllates and mineral spirits. Be aware that not all toxins are necessarily listed on the MSDS. Certain quantities of some substances are not required to be reported. Some paints are certified by third party organizations for meeting air quality standards—look for Green Seal, GreenGuard, and SCS.
- Ingredients - Binder, solvent or carrier, pigment (color), other additives.
In choosing a paint type, it's also important to consider the resources used in its production: raw materials, manufacturing processes and how its use affects the environment. How is it disposed of or recycled? Green paint choices fall into the following categories:
Conventional Low VOC Synthetic Paints
These are made from products from the petrochemical industry such as vinyl and acrylic. Colors are synthetically manufactured or may use pigments derived from heavy metals, such as cadmium and chromium. They are often created from nonrenewable resources and use energy-intensive processes. Titanium dioxide white, widely used in synthetic paints is an energy-intensive and damaging ingredient. Although a natural mineral, to make it pure white it has to be cleaned with toxic acids that contaminate the environment. These processes also contribute to CO2 emissions. Low VOC regulations vary for these paints. Absent from the VOC rating are toxic chemicals that outgas but don't contribute to ozone depletion and smog. They may also contain toxic drying agents, preservatives, fungicides and suspension agents.
Natural or "Eco" Paints
Made from renewable and biodegradable ingredients. They are low VOC and contain no ozone-depleting chemicals. These products often use lightfast, low-toxic iron oxide and manganese pigments. However, some natural paints may contain heavy metals, such as cadmium and chromium. Eco paints use a less intensive manufacturing process and makers are likely to disclose ingredients. This is especially important for chemically-sensitive individuals as they may be allergic to some natural substances. Natural paints using solvents derived from plants, such as citrus oil, may not be as damaging as synthetic solvents, but they can trigger allergies and still require adequate ventilation and curing when used in interior spaces. As with the other types of paint, it is important to investigate the components of the product.
Milk (Casein) Paint
This products usually comes in a powder form and is mixed with water at the site. It is considered permanent but not waterproof. When dry, it is odorless, nontoxic, durable, zero VOC and biodegradable. Typical ingredients are mineral pigments, casein (milk) powder, and sometimes, chalk, clay or lime for opacity.
These may be applied on paper-faced drywall. The potassium or sodium silicate binder acts chemically with drywall material to create a coating that is breathable and resistant to weathering. As with the other mineral based paints, it is odorless, nontoxic, durable, zero VOC and biodegradable. The drawback is an energy-intensive manufacturing process to create the silicate particles.
Recycled and Remanufactured Paint
Recycled paints can be in the form of a remix or come from a swap program. In remixing, several brands of paint may be combined into a single product. Remixes aren't tested for VOCs and other compounds. In a swap program, one can more clearly identify the components of the product by reading labels. Remanufactured paints are leftover (or recycled) paints mixed with compatible products and tested for VOCs. However, their content of other chemicals is unknown. The mixing process limits color choices for these types of paint.
These can be made of local pigments and binders dramatically reducing manufacturing and transportation impacts. Water is the primary carrier. Most are intended for use on porous surfaces and require expertise in mixing and application. Paint types include limewash, casein paint, clay paint and silicate paint. All may be mixed to be odorless, nontoxic, zero VOC and biodegradable.
A final consideration in choosing your green paint (or maybe it should be the first) is how it will be disposed of. Actually, it need not be disposed of. If you plan well, you may be left with just enough to save for touch-ups. If you're left with more than that, consider donating the paint to a local community assistance or housing group. You may also check with the manufacturer about recycling programs the company participates in. If leftover paint can't be handled in the above manner, check with your local landfill for hazardous waste disposal policies.
Check out these categories in the Oikos Product Directory to get started in your search for green paint:
Low VOC Paint
Zero VOC Paint