Engineered Wood Products and Formaldehyde Emissions

Although modern engineered wood has been around for over half a century, many people still harbor misconceptions about these high-strength, highly stable composite wood products. This is particularly true in the environmental field, where the public, influenced by the questionable quality of some low-grade plywood products, is generally wary of engineered wood materials that utilize glue as their primary adhesive. A major concern is formaldehyde emissions from composite engineered wood products. Today, we'd like to provide a brief explanation of this topic.

What is engineered wood?

Simply put, engineered wood materials refer to a range of large-scale or large-format architectural or decorative components manufactured through engineering processes by gluing or laminating small-size lumber or wood chips. Common examples include glulam beams and columns, cross-laminated timber (CLT), oriented strand board (OSB), structural plywood, LVL (veneer laminate), and I-joist beams. These products generally rely on high-strength structural adhesives to hold the wood together. Other engineered wood materials, such as NLT (nail-joined timber) and DLT (dowel-joined timber), have also emerged, using metal or even dowel systems for their connections.

Known for its use in striking projects, such as vaulted ceilings and other designs with dramatic expanses of space, glulam is often used for its beauty and strength in churches, schools, hotels, and other commercial buildings. Indeed, glulam possesses a timeless appeal with a quintessential natural wood appearance. Glulam products, such as CLT, have become a staple in multi-story timber projects, challenging traditional concrete. OSB is also the most widely used structural panel material, and its stable shear resistance makes it the primary cladding material for lightweight timber floors, walls, and roofs.

What is formaldehyde?

Formaldehyde is a simple chemical composed of hydrogen, oxygen, and carbon. It occurs naturally as a product of many natural processes. It is produced by our bodies and is present in the air. Plants and animals also produce formaldehyde. It is found in many fruits and vegetables and is a byproduct of cooking certain vegetables, such as kale and cabbage. This chemical breaks down quickly and metabolizes into simple carbon dioxide. Our bodies easily break down the low levels of formaldehyde we are exposed to every day.

Formaldehyde is also a combustion product associated with the burning of kerosene and natural gas, automobile exhaust emissions, and cigarettes. It is an important industrial chemical used in the manufacture of many consumer products, including permanent press fabrics and even toothpaste.

How much formaldehyde is in wood?

All wood species, and all wood products, contain and release small amounts of formaldehyde. Because formaldehyde is naturally present in wood, there's no such thing as "zero-formaldehyde" wood. For example, an oak tree emits 0.009 parts per million of formaldehyde. On its own, this is a very low amount, but dense forests can have much higher concentrations. Therefore, any wood cut from an oak tree contains small amounts of formaldehyde, as do all wood products.

Formaldehyde emission regulations

According to the website of Canada's federal government's environment department, all composite wood products produced and sold in Canada must comply with a series of federal and provincial environmental regulations. The Canadian government is also considering incorporating CSA standards into these regulations to more strictly manage the emissions of composite wood products. CSA stands for the Canadian Standards Association. Founded in 1919, it is Canada's first non-profit organization dedicated to setting industrial standards. All electronics, appliances, bathroom fixtures, gas, and other products sold in the North American market require safety certification. CSA is currently Canada's largest safety certification body and one of the world's most renowned.

According to information from APA, the world's largest organization for engineered wood products, the manufacture of structural wood products such as structural plywood and oriented strand board (OSB) meets strict product standards, including the voluntary product standard PS 1-07 for structural plywood and the voluntary product standard PS 2 for the performance standard of wood-based structural panels. Because wood products are produced according to these standards, when applied to buildings, they are manufactured only with moisture-resistant adhesives to meet the outdoor Exterior or Exposure Level 1 exposure level. These adhesives, including phenolic resin adhesives and isocyanate (MDI) adhesives, chemically react to form a stable bond during the hot press molding process. This results in the final product having low formaldehyde emission levels, complying with the following authoritative formaldehyde emission standards and regulations worldwide, or achieving inspection exemption levels:

1. U.S. Department of Housing and Urban Development Manufactured Home Standard. This standard establishes an emission limit of 0.20 ppm for non-structural plywood, as evaluated using the ASTM E1333 method. Phenolic-formaldehyde-bonded structural plywood is exempt from testing and certification due to its extremely low formaldehyde emissions. While there are no specific restrictions for oriented strand board (OSB), it is widely accepted that phenolic adhesives suitable for panels can also be used with oriented strand board (OSB) products meeting the voluntary product standard PS 2.

2. California Air Resources Board (CARB) Comprehensive Wood Products Air Toxics Prevention Regulations. This regulation, developed by the California Department of Environmental Protection and scheduled to take effect January 1, 2009, is considered the most stringent formaldehyde emissions regulation in the United States. Recognizing the varying levels of formaldehyde emissions from wood products, Definition No. 8 specifically exempts "structural plywood," "structural paneling," "structural composite lumber," "oriented strand board," "glulam," and "prefabricated I-joists."

3. According to the Japanese Agricultural Standards (JAS), wood-based structural panels are required to meet the strictest formaldehyde standards (F★★★★), using the JIS A 1460 test method, with an average emission level below 0.30 mg/L. PS1 and PS2 panels easily meet the F★★★★ requirement. This formaldehyde emission regulation for wood-based structural panels is widely recognized as the strictest in the world.

4. Oriented strand board (OSB) sold into the European market must meet EN 300 and be rated for formaldehyde emissions using the EN 717-1 formaldehyde chamber test method. Structural plywood sold into Europe must comply with EN 636 and be assessed for formaldehyde emissions according to EN 717-1. Structural plywood and OSB manufactured with PS1 and PS2 panels meet the E-1 formaldehyde emission limit of 0.124 mg/m³ in these standards.

Some information comes from: APA Engineered Wood Materials Association