The following was recently Tweeted to SIPschool, affording me the opportunity to address a misconception that occasionally rears its confused head.
“OSB Sips can not be safely recycled because of their high toxicity, sad but true, How can we replace OSB?”
The vast majority of SIPs made in North America use OSB. Is it the perfect skin? No! Like all materials, it has its pros and cons. When considering SIPs for a project one needs to consider all factors to make the best choice. Your choices may include type of core and/or type of skin. For this post, I’ll limit the discussion to OSB.
This material has some fantastic properties and is in large part responsible for the growth and development of the SIP industry as we know it today. The engineering, research and testing championed by the Engineered Wood Association (APA) have led to SIPs that are recognized by the ICC. In addition, manufacturers worldwide are producing SIPs in jumbo format 8′ x 24′ SIPs that contribute to the speed and airtightness for which SIPs are well known.
The weaknesses of OSB skinned SIPs are also well known. They include, in no particular order:
- Cultural Acceptance – many areas of the world view wood construction as temporary or cheap.
- Termites – a cellulose-based building component is susceptible in termite-prone areas
- Moisture – OSB may be an Exposure 1 rated product that can survive multiple wetting (if it is allowed to dry) but when OSB gets wet it will swell if it stays wet; structural deterioration will follow.
- Fire – Yes, wood burns. However, the testing of finished assemblies show defined levels of performance based on cladding and detailing.
This list of four issues is real and can be accounted for up to a point. In my opinion the hardest one to overcome is cultural acceptance. If you don’t believe me, go to the Middle East or South America and try to sell an OSB skinned SIP. The other three items on my list can be overcome with good design and detailing, and quality of material and installation. That’s not to say I would recommend OSB in all cases and in all locations. I have experienced success with a number of products that compete with OSB. The future of the SIP industry will include many options, including metal, cement, magnesium oxide, fiberglass, and other hybrid skins, each with their own list of pros and cons.
The suggestion that OSB is toxic and non-recyclable is inaccurate and reflects a lack of familiarity with the manufacturing of modern SIPs. I’ll assume (as dangerous as that is) that the Tweeter is referencing formaldehyde. The concerns over urea formaldehyde are real and have severe consequences in cases of excessive exposure (think RVs used for housing Katrina survivors for years). What the tweeter may not know is that the OSB industry, under the guidance of the APA, uses resins (glue) that binds the wood strands together using trace amounts of phenol formaldehyde. The difference between the two is substantial and if you research the issue you will discover that the amount of formaldehyde present in test chambers is less than is often found outdoors. R-Control Technical Bulletin 2013 Formaldehyde Levels