VOC is a Widely-Used Term in Green Building, But Do You Understand It?
The term VOC is the most-widely-used term in green building, but a look of panic usually crosses the average yard man’s face when he’s asked to define or explain them.
Very simply, a VOC is a “carbon-based” chemical compound that evaporates at room temperature. Gasoline is a VOC, because it is a hydrocarbon and fumes pour off it at nearly any temperature.
How did VOCs end up in building products? Well, for products that dry or cure—like caulks, sealants, adhesives, and paints—they have to be applied in liquid form. To make paint, urethane, rubber, glue, etc. temporarily into a liquid so it can be applied, you need a solvent. Until these products were re-engineered to use water as a solvent, many manufacturers used (or still use) chemicals that are VOCs. For instance, if you want a rubber sealant between two building materials (e.g. wood and a counter top), you can’t apply stiff rubber. So, the rubber is liquefied with xylene or benzene, both petroleum derivatives, and both VOCs. The VOCs “flash off” (evaporate) to leave the stiffened rubber behind. Unfortunately, when VOCs flash off, the fumes can enter people’s lungs, living spaces, and the atmosphere, and that’s when the trouble starts.
Everyone universally believes they are bad for your health and should be reduced or avoided. Why?
Depending on their concentration, VOCs can cause “eye, nose, and throat irritation; headaches, loss of coordination, nausea; damage to liver, kidney, and central nervous system. Some organics can cause cancer in animals; some are also suspected or known to cause cancer in humans,” according to the ever-cautious EPA. And VOCs react with sunlight and the atmosphere to create smog.
That said, VOCs do play an important role in the performance of some products, and it may be that you take a “hit” by using a product that has some VOCs, so you achieve superior performance and a more durable (and therefore greener) finished product, like a waterproof wood finish or a harder floor finish. On balance, it’s greener in the long run to use a finish with some VOCs than to use a less-durable product that needs to be stripped and refinished three times more often.
The same principle is true with urethane caulks and sealants. In the area of caulks and sealants, a pure urethane product off-gasses just CO2, but some products have VOC solvents that act as surface primers, so the caulks and sealants get better seals and offer better performance.
Also note that some products contain VOCs, yet they don’t get into the atmosphere at concentrations that are dangerous. Formaldehyde is one of those VOCs. A carcinogen commonly used in adhesives (sheet-good wood products, MDF, and batt insulation), formaldehyde in products that are “low-emitting” do not create a known health hazard. In fact, OSHA regulates formaldehyde and has adopted permissible exposure levels. In the past, some insulation companies have put formaldehyde in their insulation (its in the adhesive that binds the fiber), but they have the product tested by a third-party, or they have subscribed to the toughest state standards, like California’s, to show the formaldehyde does not off-gas at hazardous levels.
Where you mostly find VOCs is in paints, finishes, caulks, sealants, and adhesives. Here, the EPA has set the standards. For products to call themselves “Zero-VOC,” they must contain less than 5 grams of VOC per liter. For products to call themselves “Low-VOC,” they must contain < 250 grams per liter. (Or <380 G/L for alkyd paint.) Look for Zero-VOC or Low-VOC products as your greenest alternatives.