Surrounded by giant slabs of cross-laminated timber
September 26, 2020 12:12 AM   Subscribe

Austrian Wood Providing Answer to World's Concrete Problem - "For Austrian timber merchants, who cover about half the world's CLT demand, the material is a bridge linking the digital age to three centuries of forest management begun by Hapsburg Empress Maria Theresia. She saw Austria's forests as a national-security resource and mandated strict sustainability laws."
CLT uses a high-tech manufacturing process that turns ordinary wooden planks, often made from the nearby Spruce trees, into structures that can bear thousands of tons of weight. Architects from Australia to Scandinavia and the U.S. have been buying from Huter as they leapfrog each other in a race to construct the world’s tallest wooden skyscraper. Vienna made an entire new city quarter out of CLT. Designers in Japan have planned a 350-meter (1,148-foot) tower.

Huter pointed to a project at 55 Southbank Boulevard in Melbourne, Australia which used his timber to add 10 stories onto a six-floor building, more than doubling its height and living space in less than a year. Because wood weighs just 30% of concrete, CLT is being used to expand scarce space in cities by building higher. Construction time is quicker than pouring concrete on site, resulting in lower labor and equipment costs.

Builders emit more than a fifth of the greenhouse-gas emissions spewed into the Earth’s atmosphere every year and convincing them to adopt greener materials -- which include hemp and even straw -- will be key to keeping global temperature increases well below the 2-degrees-Celsius (3.6 degrees Fahrenheit) mark mandated by the Paris climate accord. But it’s not just CLT’s potential to rapidly put the brakes on emissions that’s behind demand.

Using timber “significantly reduced” construction time, according to Bates Smart, the architectural firm that designed 55 Southbank. Wood in the structure sequestered some 4,200 tons of carbon dioxide, equal to the annual emissions of 130 homes.
What 'net-zero carbon' really means for cities - "The built environment is responsible for around 40% of the UK's total carbon footprint, according to the UK Green Building Council – and is another aspect of the city that needs to be rethought to achieve net-zero status."
Analysing the amount of carbon emitted per cubic metre of each material, the project demonstrated that glass and steel were among the materials with the highest carbon impact, while more sustainable, low-carbon options include brick, stone and cross-laminated timber (CLT) – especially if they are locally sourced. Steel, for instance – which is often used for building skyscrapers – is responsible for at least 7% of global CO2 emissions, releasing 12.2 tonnes of CO2 per cubic metre used, in part due to the heating process involved in making it. Concrete produces 550kg (1,200lb) CO2 per cubic metre used, but its main ingredient, cement, is responsible for about 8% of global CO2 emissions due to its widespread use as cities rapidly develop.

Timber has much lower embodied carbon, however, and CLT is actually a carbon negative material (sequestering more carbon than it emits). CLT is made from trees grown for around 40 years in a managed forest before being harvested, cut and pressed together with adhesive. The trees absorb and sequester carbon as they grow, so that CLT effectively absorbs 600kg (1,300lb) CO2 per cubic metre. CLT is also strong enough to be used structurally, with quick construction and reduced waste. (Read more about timber buildings as a solution to climate change)
posted by kliuless (28 comments total) 30 users marked this as a favorite
 
So, my question is... fire? The only time it's mentioned in the main article is mentioning how forest management by harvesting wood for building could prevent wildfires. But what about structure fires?

If you're going to build a sixteen-story wooden building... that's sort of... I mean, I wouldn't move into one.
posted by hippybear at 12:34 AM on September 26, 2020 [3 favorites]


Counterpoint to the recently raging CLT fever-dream: To Save Our Climate We Need Taller Trees Not Taller Wooden Buildings
posted by progosk at 12:42 AM on September 26, 2020 [7 favorites]


hippybear -- Compared with steel or concrete, CLT, also known as mass timber, is more fire resistant. When exposed to high temperatures, steel loses strength and begins to deform and fail catastrophically (eg the WTC collapse). Cross laminated timber not only retains its structural strength at high temperatures, it also self protects against combustion - the surface chars to black carbon, and as timber is non-conductive the heat does not penetrate to the interior of the timber, and does not transmit to the other side of the timber either (the next room).
posted by xdvesper at 2:09 AM on September 26, 2020 [31 favorites]


I’m eager for my first project to build with CLT. It’s not a panacea and there are already questions about true sustainability (pro-tip: it comes down to forest management practices of the source timber). But, it’s a step in the right direction. We just need affordability to come to the realm of everyday projects, and not be so focused on racing upwards.
posted by meinvt at 4:46 AM on September 26, 2020 [5 favorites]


What’s the long term stability of CLT? The forest products lab here in town recently took apart the second oldest glulam structure and tested it. It performed pretty well!

Are the glues in modern CLT similar to these, or are they different?
posted by rockindata at 5:19 AM on September 26, 2020 [2 favorites]


This is all super cool. Thanks for the post and the discussion too!
posted by Alex404 at 7:24 AM on September 26, 2020 [1 favorite]


rockindata, there’s a lot of longer-term research in Europe that indicates CLT is a durable construction method but a recent failure in Oregon put the damper on West coast efforts a bit. The post-incident analysis indicated that the issue was in quality control in manufacture, not in material choices. All “new” methods have a learning curve.
Underlining the truth that steel buildings are not inherently fireproof- I can believe that mass timber is effective in a fire precisely because the protection method described is so similar to spray-on fireproofing used on steel.
posted by q*ben at 7:46 AM on September 26, 2020


This seems awesome, but also it looks like the structural properties are great because wood has great structural properties, and it's sustainable because wood is sustainable (when you do it right), etc... so is the point that wood is a good material?

Also, how, in principle, is this not plywood? I mean, I'm a fan of plywood, but is the main contribution here that someone figured out that you don't need that many plies? Or is it more useful because there are better industry standards? The cross-lamination part can't be new, can it? I guess maybe I'm just wondering how (and if) this hasn't been around since the 1600s...
posted by kleinsteradikaleminderheit at 8:51 AM on September 26, 2020 [2 favorites]


"It is similar to plywood but with distinctively thicker laminations (or lamellae)."

https://en.wikipedia.org/wiki/Cross-laminated_timber
posted by Nancy Lebovitz at 8:56 AM on September 26, 2020 [4 favorites]


Plywood plies are "peeled" off a log and then glued together, so you're already introducing stress by converting the circumferential spirals into flat sheets. IN CLT, the plies are regular sawn sections.

The reason this hasn't been around since the 1600s is glue. Until the industrial age, "hide glue" was the name of the game - thus the joke about old horses and glue factories. Hide glue is great for furniture, but it's not waterproof. This is handy if you ever need to take a joint apart, but not something you want in a structural member. Thus, wood-composite structural members weren't plausible until waterproof glues came on the scene.
posted by notsnot at 10:12 AM on September 26, 2020 [8 favorites]


An alternative that's pretty nifty: brettstapel.

...the Oregon failure, given US propensity to do things as poorly as possible, is going to put a damper on adoption unless suitable testing methods can be developed. I expect Authorities Having Jurisdiction to either require pretty onerous QA/QC and fabrication inspection requirements until they can test post-assembly and assure themselves that the gluing is sufficient.

This is not unique to CLT -- the building industry here is driven by these kinds of reactive requirements. Just about every time people decide to back off on requirements, they back off too far, bad things happen, they ratchet up the restrictions again, and the cycle continues as we slowly slowly slowly find equilibrium over decades.

The other two things I expect AHJs to potentially freak out about is water damage (what happens if the sprinkler system is activated? Have you just destroyed the building?), and insect damage (will they require a crapton of hideous poison to be infused into the wood?).
posted by aramaic at 10:29 AM on September 26, 2020 [3 favorites]


"Builders emit more than a fifth of the greenhouse-gas emissions spewed into the Earth’s atmosphere every year"

I did not know that.

This is really interesting. Thank you for posting it, kliuless!
posted by kristi at 10:44 AM on September 26, 2020


@notsnot
Thanks! Asking dumb questions on metafilter (and/or melamine urea formaldehyde/polyurethane adhesives) FTW
posted by kleinsteradikaleminderheit at 11:01 AM on September 26, 2020 [2 favorites]


Is this cheaper then concrete/steel structures? My understanding is that beyond six stories a traditional wooden structure becomes infeasible and that steel is almost 10x the cost per floor to build. Feel free to tell me my assumptions are wrong.

I would think that any sort of environmental damage would be made up for denser urban areas. Dense urban areas like NYC or London get tremendous economies of scale and benefits from people and goods not needing to travel anywhere. Land use, carbon emissions, etc. But people want suburban living not just for the convenience but for the physical space. 3 kids anywhere is expensive let alone in a dense urban area where it requires dedication to living in an incredibly confined space. If this allows 2,400 sq ft or whatever the typical suburban cookie cutter home to fit in a mini-skyscraper it might drastically change the perception of urban living.
posted by geoff. at 11:57 AM on September 26, 2020


One of the things that alway bugged me about CLT was the planes being flat and the 90 degree angle of the planes. Shear strengths of adhesives are typically far below that of steel or even concrete so that seems to me to be a weak spot.

Would it be possible to produce a CLT that has a mechanical joinery interlock between the planes along with the adhesive to make it more resistant to shear and subsequent delamination? Or would that just plain cost too much or make production too annoying?
posted by Your Childhood Pet Rock at 12:30 PM on September 26, 2020


Modern wood glue is generally stronger than the wood itself, so the wood is the limiting factor for shear strength, not the adhesive.
posted by ssg at 1:00 PM on September 26, 2020 [1 favorite]


I would be pretty shocked if the shear strength of a modern adhesive on its preferred substrate was lower than that of concrete.
posted by maxwelton at 1:49 PM on September 26, 2020 [1 favorite]


In a perfect system, yes. But what about out in the field where you have all sorts of environmental factors attacking the adhesive not to mention the tools contractors use. A panel may have that nice edge milled with a proper compression cutter in the factory but when some contractor pushes their old, blunt drill bit through the nice new composite it's going to cause burrs and lots of spots to give delamination a point to start from.

Maybe I'm just too old school to realize just how good modern adhesives are. All of my knowledge is carpentry from working with my dad and glue is like that thing you use to keep joinery together not keeping two pieces together.
posted by Your Childhood Pet Rock at 1:59 PM on September 26, 2020


I recently posted a link about coppicing and pollarding:
A coppice can be called a “coppice forest” or a “coppice plantation”, but in reality it was neither a forest nor a plantation – perhaps something in between. Although managed by humans, coppice forests were not environmentally destructive, on the contrary. Harvesting wood from living trees instead of killing them is beneficial for the life forms that depend on them. Coppice forests can have a richer biodiversity than unmanaged forests, because they always contain areas with different stages of light and growth. None of this is true in industrial wood plantations, which support little or no plant and animal life, and which have longer rotation cycles (of at least twenty years).
People made and make structures using coppiced wood. But they sure aren't skyscrapers!
posted by aniola at 4:06 PM on September 26, 2020 [3 favorites]


^interesting essay about coppicing.. Silviculture is a thing mentioned in the later part of Annie Proulx's novel Barkskins, which is an excellent (and often depressing) historical novel about the history of forestry in North America.
posted by ovvl at 5:11 PM on September 26, 2020 [1 favorite]


This sounds really good, but what about the glues being used? My question would be how toxic they are and what are the long term health and environmental effects from them.
posted by blue shadows at 7:05 PM on September 26, 2020 [2 favorites]


The art of decommissioning concrete/ rebar highrises is pretty well developed. Has any research been done on how to break these apart at end of life?
posted by porpoise at 7:49 PM on September 26, 2020


Re: glues, I'm no longer up to speed on all of the various formulations but broadly speaking they're:

PUR: polyurethane
EPI: emulsion polymer isocyanate
MF: melamine formaldehyde
PRF: phenol resorcinol formaldehyde

Generally speaking, PU performs poorly in fires (some formulations are significantly better, however), EPI is next-worst, and then the others are (iirc) roughly the same.

With respect to formaldehyde, a number of building codes specifically exempt engineered wood products from having to meet formaldehyde requirements on the assumption that the chemical will be "locked up" within the glue and therefore not a VOC. This is probably a reasonable assumption based on experience to date, but this is one of those things where it will only take one fuckup by a manufacturer to set everyone back a few years. Given the Oregon failure, I frankly expect such a fuckup to occur at some point.

As a separate matter, wood produces formaldehyde by itself. (pretty low levels) This is sometimes used by industry as a reason why you don't need to care about formaldehyde (because it's "natural") but that's wrong. Lots of terrible things are natural.
posted by aramaic at 7:55 PM on September 26, 2020 [3 favorites]


Mass timber is exciting, not only for its potential in addressing climate change, but also because it could revive rural economies and promote better forest management:
In 2015, CLT was incorporated into the International Building Code (IBC), which jurisdictions across the US adopt as their default. A set of new changes that will enable mass timber structures up to 18 stories tall have been accepted and are expected to be formalized into the newest IBC code in 2021.

Some jurisdictions in the US have been aggressive about supporting mass timber, including Washington and Oregon (which have preemptively accepted the new changes to the IBC; Oregon incorporated CLT as a “statewide alternative method” in 2018).

The Pacific Northwest is understandably excited about a possible shift to wooden building materials, as it is home to copious forests and idled sawmills.

“Timber harvest in [the Pacific Northwest] has declined significantly as a result of the weak domestic demand during the housing crisis, which has been devastating to the forest products industry,” reports a recent study of CLT lifecycle emissions. “In Washington State, the volume of lumber produced declined 17% between 2014 and 2016 and, compared to 10 years ago, lumber mills (the largest sector by timber consumption) produced one third fewer boards.”

Nationally, forests are so overstocked that the Forestry Department is giving out $9 million in grants for new ideas for how to use wood. Plenty of local communities would welcome new demand. ...

Forests in the West have become tinderboxes, in part thanks to climate change and in part thanks to years of poor management. They are filled with trees dead or weakened from pine beetle infestations. Decades of overzealous fire protection have left them choked with closely clustered, small-diameter trees. Lately, with all this kindling around, “there’s so much fuel, the intensity of the fire wipes out everything,” says Hilary Franz, commissioner of public lands in Washington state. The land is being permanently scarred.

The forests on public lands badly need thinning, but there’s never enough funding. This has given Franz an idea: use weak and small trees, for which there is no other market, for mass timber. (Logs with tops as small as 4.5 inches will work.) A sufficiently large market for mass timber would create funding for thinning those trees out. As a bonus, Franz wants to use mass timber to build low-cost affordable housing on publicly managed land.
posted by Artifice_Eternity at 10:47 AM on September 27, 2020 [1 favorite]


This is a decent article about various types of manufactured lumber and it has a few examples of buildings made of each.

This is kind of a fun demo of a steel beam vs a wood beam in tiny test houses.
Wood vs fire-proofing I'm not sure it's fully scientific, but basically shows that wood has predictable burn rate and that the burn rate is not that different for wood framed vs steel framed buildings.
posted by The_Vegetables at 12:12 PM on September 28, 2020


As Concerns Over Climate Change Rise, More Developers Turn to Wood - "With environmental benefits and lower labor costs, mass timber has grown into a market that could rival steel and concrete in the construction industry."

The Trees and the Forest of New Towers - "As engineered wood evolves as a construction material, the sky is becoming the limit for timber office and institutional buildings."

Let's Fill Our Cities With Taller, Wooden Buildings - "Trees are some of our best allies in solving the climate crisis."

Log Cabins? No, These Wooden Buildings Are High-Rises - "Seeking greener projects, builders are choosing timber for offices and apartments, rather than the concrete and steel that dominated construction for decades."

Looking at Timber and Seeing the Future of Home and Business - "Seen as practical and elegant, wood is being reimagined for the needs of modern urban environments, and at ever-increasing heights."

Wood That Reaches New Heights - "Cross-laminated timber, a sort of supersize plywood, is already popular in Europe in ever-taller buildings that can be a cheaper and environmentally friendly alternative to traditional buildings."

Building With Engineered Timber - "The Graphite Apartments, a nine-story residential tower in London, is one of the tallest timber buildings in the world. It is constructed of factory-made solid-wood wall and floor panels called cross-laminated timber, or CLT."
posted by kliuless at 9:06 PM on September 28, 2020


"Trees are some of our best allies in solving the climate crisis."

As per the direct answer to this piece in the CLT-critical article I linked above:

We agree wholeheartedly with Lowenstein et al. when they said in a New York Times opinion piece last fall, “Trees are some of our best allies in solving the climate crisis.” But to do so, they need to be allowed to grow to maturity wherever possible. Policies to do this have been crafted and introduced. Decision makers need to embrace these rather than the false solutions offered by wooden skyscrapers and cross laminated timber.

To lunge headlong into an era of woodscrapers, blind to updated LSA analyses of materials and to a more comprehensive consideration of all the consequences of a new timber rush (on full-tally emissions, but also sequestration, on-land carbon storage capacity, and land climate resilience) would, erm, literally mean missing the forest for the trees...
posted by progosk at 12:48 AM on September 29, 2020


Glulam is used many places here in Norway. Have a look at the (now deserted due to the circumstances) newest addition to Gardermoen Airport, or this slideshow of different structures. Heck, even my closest grocery store is solid wood now (they won a prize for this).
posted by Harald74 at 4:28 AM on October 2, 2020


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