Is formaldehyde offgassing from plywood or OSB an issue in a chicken coop?

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I got this question from a coop builder a few months ago:

“A friend saw that I had bought OSB [oriented strand board] and mentioned that this was a potential hazard due to formaldehyde emissions. What are your thoughts on this? Am I better off returning it and going with plywood?”

Some background first. Formaldehyde is used in the resins (glues) of some manufactured wood products like plywood and particle board. The emissions the builder was concerned about are often referred to as “offgassing” or “outgassing,” which is the gradual release or evaporation of chemicals from a building material. If these vapors build up in an enclosed space, like a car or home, it could lead to a problem. But what about in a chicken coop?

In a properly ventilated chicken coop, offgassing of formaldehyde is not a problem, because the gasses simply don’t build up. That said, you still may wish to limit your use of offgassing materials whenever possible.

Here are some facts and guidelines about formaldehyde in plywood and OSB that can help you when building a chicken coop:

  • Formaldehyde is used in the binders and resins of some manufactured wood products.
  • Offgassing can be an issue with products containing urea-formaldehyde (UF) resins. These tend to be products rated for interior use (e.g., particleboard, hardwood plywood paneling, and medium density fiberboard)—which is ironic, since it’s inside well-sealed homes where gasses tend to build up.
  • Exterior plywood and OSB do not contain urea-formaldehyde (UF) resins. Instead, they use phenol-formaldehyde (PF) or isocyanate resins. Phenol formaldehyde has extremely low offgassing. Isocyanate resins have no formaldehyde emissions at all.
  • You may see these exterior-rated products labeled as exempt from formaldehyde certification requirements. That’s actually a good sign. It means they don’t contain UF, the more offensive kind of formaldehyde.

A good rule of thumb, then, is to use exterior-grade products. Easy enough. Actually, the vapor buildup you really need to worry about is ammonia from the chickens’ waste. This can build up to toxic levels quickly and affect your hens’ sensitive respiratory systems.

So choose the right materials, of course. But, more importantly, pay attention to your design and ventilate your coop!

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