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面向建筑商避免stran虽然怀疑d board (OSB) when it was first introduced commercially in the 1980s, today it dominates the U.S. sheathing market, far outstripping plywood with about 64% of sales. Improved resins, better water-resistance, and especially lower costs have helped make OSB the first choice for many builders even though plywood production can be counted in the billions of square feet annually.
From a structural standpoint, OSB and plywood share many performance characteristics and can be used interchangeably in a given application. Both are engineered wood products. “The amount of wood and the equipment to process them is a little different but it’s still the same basic concept,” says Dr. Joseph Loferski, a professor in Virginia Tech’s Department of Sustainable Biomaterials. “You’re going to take a tree, chop it into smaller pieces, put glue on it, and glue it back together. That’s basically the process.”
In comparing these two panel products, many of the fundamentals haven’t changed much since Sean Groom took a deep dive inthis articleforFine Homebuildingmagazine back in 2005. Yet the question of which one is better still pops up, especially as the dynamics of building assemblies change. Tighter building enclosures and more insulation have made builders more sensitive to the nuances of moisture management and air control. Those focused on sustainable design are starting to ask questions aboutembodied carbon—a topic that wasn’t on the radar a decade and a half ago.
Water-resistance is still a factor
How these panel products react to water was, and is, a key difference. Plywood is a sandwich of thin plies of wood, with grain direction alternating 90 degrees from one ply to the next. OSB is a mat of wood strands compressed under pressure and heat into a…
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6 Comments
The link for Fine Homebuilding magazine didn't work for me.
Its also worth noting that the small Huber study on the airtightness of the OSB was done to ACH75 -ACH300, and the Code requirement for airtightness is in ACH50. Kind of a dubious "marketing" study if you ask me. Its a shame, that comparing apples to oranges get so much interest.
For what is worth, many of us use OSB in our building assemblies, paying special interest in sealing details to achieve consistent low numbers, from .6ACH50 to 1ACH50.
Armando,
I fixed the link. Thanks for letting us know.
Hey Armando--I don't know if the FHB article had a units error, but the GBA writeup uses the correct units--50 to 300 Pa (not ACH 50), which is the kind of pressures you need to get a measurable signal out of something like OSB.
"Initially, the study was designed to measure the air permeance of three types of sheathing: 15/32-in. plywood, 7/16-in. OSB, and 7/16-in. Zip. Phase 1 of the project was to measure permeance and find out what effect wetting and drying cycles would have on them. They used a standard testing method (ASTM E2178) to check air-leakage rates under pressures that ranged from 25 to 300 Pascals (Pa).
What constitutes an air barrier? For purposes of this study, RDH used a standard criteria of 0.02 liters per second per square meter at 75 Pascals of pressure (lps/m2). If a material allows more air than that to get through, it’s not effective as an air barrier."
"Asked whether using OSB is any riskier than using plywood in a higher-performance wall assembly, Kohta Ueno, a senior associate at Building Science Corp., said it’s easy to generalize."
Based on the subsequent quote, I think there's a "not" missing from the end of that sentence.
Great article, Scott. If you run a BEES analysis between OSB and plywood, the environmental impact of OSB is significantly greater than plywood. BEES, or Building for Environmental and Economic Sustainability, a software developed by NIST to evaluate the environmental impact of comparable building materials, takes broader criteria than carbon.
Fernando, that is interesting.
My first reaction would have been that OSB is easier on the environment, compared to plywood. Both use adhesives, but osb can salvage more wood per logs of varying quality, right? With fewer plywood quality logs becoming available each year (large assumption on my part), does the comparison really matter if plywood becomes limited in availability?
Curious to hear more,
Thanks!
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