The Rise of Tall Wood

This is a series where I take my lectures presented as adjunct professor teaching sustainable design at Ryerson University School of Interior Design in Toronto, and distill them down to a sort of Pecha Kucha slide show of 20 slides that take about 20 seconds each to read. Wood has been used for tall buildings for a very long time; the Church of the Transfiguration in Kizhi Pogost built in 1708, is still probably the biggest and tallest wood building in the world, at 123 feet or 37.5 meters. But wood fell out of favor; much of the big and accessible stuff got chopped down, and wood burns, as cities like Chicago and Tokyo found out. When steel became common and affordable it took over the tall building world, along with poured reinforced concrete.

As climate change became an issue in the last two decades, architects and engineers started looking at wood again as a way of reducing the carbon footprint of our buildings. Concrete, in particular, has a huge carbon footrprint, responsible for as much as 5 percent of the CO2 released each year. It's the chemistry; to make cement you have to heat limestone to 1450 °C, which liberates a molecule of CO2 and turns it into calcium oxide, or quicklime, the active ingredient in cement, which is then mixed with aggregate to make concrete. With wood, it's the biology; CO2 is absorbed by growing plants and trees, converted through photosynthesis into cellulose while releasing oxygen. Wood is essentially sunshine and water turned into solid form. When a tree dies, the wood rots and releases that stored CO2; when sustainably harvested it stores it for the life of the building, which can be hundreds of years. As the table shows, it beats steel and concrete in every environmental criterion.

For hundreds of years, the forests of North America have been clear-cut of the giant first growth trees, and much has been replaced by second and third growth forests. The industry has also learned how to harvest more sustainably, and most forests are now cut according to standards like FSC, CSA or SFI. Often when we write about wood construction we get attacked by those who say that we are encouraging deforestation, but the real concern there is for the rainforests being lost in South America and Asia. In fact, in North America, much of the forest is threatened by the Mountain Pine Beetle, which has killed vast swathes. Harvesting this before it rots would be good for the forest and the atmosphere. The Engineers at Arup summarize its benefits:

• Timber is the only 100% renewable building material
• Timber locks up carbon for the life of the building
• Because it’s a cellular material like bone, wood is strong and light
• This lightweight cellular structure also makes wood a natural insulator
• Easy to prefabricate and transport, timber makes for quick construction
• Timber is attractive and can be left exposed, reducing the cost of finishes

The first big wood building to gain a lot of notice worldwide was the FMO Tapiola building from 2005. It was tough, building in wood then, even in a country like Finland that was covered with the stuff. Structural engineer Jukka Ala-Ojala was quoted in TreeHugger in 2006 and it seems that the problems he faced then are what every architect working in wood in North America faces today:

The wooden structures are complicated and as wooden technology has not been used to this extent before, it has been a steep learning curve for the whole team. One particular achievement was convincing the authorities that the building would meet the stringent European safety codes.With no previous experience of such a complicated wooden structure in office construction, they were particularly concerned about the fire risk.

But architect Pekka Helin was optimistic and prescient:
A modern wooden office building shows how wood can meet today's architectural demands for more 'human' and environmentally-friendly structures. I see a bright international future for such buildings as the wood renaissance continues.

But the real breakthrough for tall wood was the timber apartment building designed by Waugh Thistleton architects and built out of Cross-Laminated Timber (CLT) in 2007. At the time the nine storey building was the tallest residential tower in the world. It was assembled in nine weeks by four workers with less dust, disruption, and a far lower carbon footprint. This is the building that put Cross-Laminated Timber on the international map. More: Waugh Thistleton's Timber Tower Nine Storey Apartment Built Of Wood in Nine Weeks By Four Workers

Cross-Laminated TImber (CLT) was developed in Austria in the mid 1990s; the photo shows the factory of KLH, which is the leader in the industry. It is made by taking kiln-dried lumber and setting it up with layers at 90 degrees to each other, with adhesive in between layers. It's then compressed in hydraulic or vacuum presses. It has been called "plywood on steroids". It is very strong in all directions, is resistant to shrinkage thanks to the wood running in two directions, and panels go together quickly. More and more authorities are allowing it into their building into their building codes. Because it's new, it gets most of the press these days, but it is not the only way to build out of massive wood. More on CLT: Cross Laminated Timber is Ready for Prime Time Interlocking Cross Laminated Timber Could Use Up Square Miles Of Beetle-Killed Lumber, and Look Gorgeous, Too

Much older than CLT is glulam, or glue laminated timber. It was used in the Richmond Oval skating rink built for the Olympics, and has been used for skating rinks across Canada since the sixties. Unlike CLT, the wood is all lined up in one direction, so it's really used to replace heavy timber. However it can be formed into curves and complex shapes as well. It has been around for a long time, first patented back in 1892. However it really took off in North America in 1942 when steel was needed for the war effort and Glulam was developed as an alternative. It is made with a waterproof glue so it can be used indoors and out. Here's the highest glulam wood building in the world, Herzog & De Meuron's restaurant at the end of the cable car is a prefab wooden wonder

Another even older technology making a comeback is Nail Laminated Timber, or NLT. It's what we used to call mill decking, and it really is nothing more than a bunch of dumb planks nailed together. And in fact, if you are doing a simple span, it does the job just fine, costs a lot less, and has been covered in every building code forever so it's a lot less work to get approved. Obviously some of the things they are doing with it are not so dumb and simple, such as this great roof designed by Perkins + Will and built by Structurecraft. More : The old is new again with Nail Laminated Timber

The Bullitt Center in Seattle, considered by many to be the world's greenest building, is made of a mix of glulam columns and beams, with nail laminated timber running between them as the flooring structure. This is the way industrial buildings were built in North America since about 1850, albeit with heavy timber instead of glulam. Now no big trees are harmed in the construction of buildings, it is earthquake resistant strong. They explain:

Glulams make efficient use of wood by bonding smaller pieces together to form larger components. This creates a strong, dimensionally stable and consistent product with the ability to span great distances. Using glulam timbers allows for a larger final product than using dimensional lumber, and they can be produced from lower grades of timber. During the fabrication of a glulam timber, there is only a 3% material waste.

Then there is what might be the Next Big Thing, Brettstapel, where the wood is held together by dowels.

This innovation involved inserting hardwood dowels into pre-drilled holes perpendicular to the posts.... This system is designed to utilise a moisture content variation between the posts and dowels. Softwood posts (usually fir or spruce) are dried to a moisture content of 12-15%. Hardwood dowels (mostly beech) are dried to a moisture content of 8%. When the two elements are combined, the differing moisture content results in the dowels expanding to achieve moisture equilibrium which locks the posts together.

Like NLT, this is a process that can be used on big or small buildings, has no glue, and you could do it in your garage. More: Why this mountain bike center is built of Brettstapel, and why North American builders should be using this stuffBrettstapel: another way of building with woodScottish architect's Design-Build company MAKAR is doing wonders with wood

And for something completely different, there is the work of FACIT, where they come to a jobsite with a shipping container holding a big CNC machine and a pile of plywood. Before you know it they have cut up the wood and nailed it into cassettes which two people can then lift and assemble the entire house or building; just follow the numbers. It's a form of 3D printing, straight from computer to cutter. Totally different from everything else here, but It is one of the most interesting innovations in wood construction, and one that I believe we will see a lot more of. More on Facit: 1:1 Making the Digital House Mind-blowing Digital 3D Printing of Super-Green Houses is Happening Now This gorgeous treehouse is a computer printout Digital fabrication will revolutionize architecture, and FACIT shows how it's done

One of the biggest complaints about wood construction is the risk of fire, but in fact in massive timber, the risk is pretty low. It's been known for hundreds of years that when wood burns, the exterior char actually acts as an insulator and protects the wood below. It continues to char at a known rate, so that if you want a two hour fire rating, you add enough extra wood to your structural needs to have two hours of protection. We also have sprinklers and fire alarms that they didn't have in the last wood construction boom. There are still fires, but they happen mostly during the construction phase, and construction practices are changing accordingly. Read more on wood and fires, complete with spectacular photos: Construction fires are not an indictment of wood construction Wood frame construction is safe, really.

In the UK and continental Europe they have been doing wonderful things in modern wood technology, but it is just making its way to North America. One of the first CLT houses on the continent (and I think one of the loveliest) is Seattle architect Susan Jones' own house, which I visited during construction. That's me and her, in front of a wall that she had routed out to make a decorative element; there is a big window on the outside covering it all. The entire house, floors walls and ceilings, are all exposed CLT. It's then wrapped in a blanket of insulation and clad in the material du jour, shou sugi ban. More on Susan's house: CLT House by Susan Jones shows the future of sustainable, green and healthy housing Susan Jones' Seattle CLT house is a wooden wonder

In Sudbury, Ontario, LGA architecture is just completing the new Laurentian Architecture Laurentienne (LAL) where they are going to specialize in the study of wood construction. The connection details are fascinating; you can see the end of the glulam beams sticking through the CLT and the steel brackets below. The beams and panels all come with slots routed out so that the connecting brackets can just be bolted through. That's why it goes up so fast. More: Laurentian Architecture Laurentienne: A school built out of Cross-Laminated Timber

In British Columbia, Canada, John Hemsworth designed a stunning factory for BC Passive House (BCPH) that shows how even industrial buildings look better in wood. It demonstrates "their commitment to wood design and sustainable construction practices." More: Factory built of wood is energy-efficient, healthy, and beautiful Lloyd Alter

Then there is the Centre for Interactive Research and Technology, which challenges the Bullitt for being the greenest building in North America. It's "a platform to test and showcase the technical performance and usability characteristics of the building’s technologies and systems, and to generate new knowledge about how to construct and maintain sustainable buildings." According to the University of British Columbia:

The wood used in the project will store an estimated 600 tonnes of CO2. As a result, the four-storey project will store 75 tonnes more CO2 than is emitted during the production of its building materials. Beetle kill wood has accounted for the largest amount of greenhouse gas emissions (GHG) in the province, more than all of the province’s human activity combined, more than motor vehicle emissions, and nearly double the output of Alberta’s oil sands. Yet this damaged wood is the same high quality as other B.C. lumber if it’s harvested within a few years of being attacked. Using it prevents carbon from escaping decaying trees. It also clears space for new growth.

More: Inside CIRS at University of British Columbia -- "North America's Greenest Building"

Currently, the tallest wood building in North America is Michael Green's Wood Innovation Design Centre in Prince George, British Columbia.

The design incorporates a simple, ‘dry’ structure of systems-integrated CLT floor panels, Glulam columns and beams, and mass timber walls. This simplicity translates into repeatability of the system. Instead of focusing solely on a showpiece structure, we created a building that can be easily replicated.

It's a sneaky building; it is the tallest because the building code doesn't say how high a floor can be and it doesn't count mezzanines. So it is a six storey building pretending to be eight. And it is beautifully done. More: A look at Michael Green's Wood Innovation Design CentreMichael Green is building North America's tallest wood building in Prince George, BC

Then there are the buildings on the boards; North America is going for tall wood in a big way now. In New York City, SHoP is building 475 West 18th, one of two buildings that won a recent competition:

475 West 18th’s extensive use of wood structural elements and other wood products allows the team to set ambitious sustainability targets in the building’s design, construction, and operation. By combining aggressive load reduction with energy efficient systems, the project team anticipates reducing overall energy consumption by at least 50 percent relative to current energy codes.

But there are other great attributes to wood construction; I asked project architect Amir Shahrokhi about it when I was at Greenbuild. My transcription:
There have been quite a few studies done about how being in a wood building, surrounded by timber, affects our psychology. It's been shown that it's uplifting, it lowers our heart rate, it's generally a very, very satisfying experience. It's going to be a big part of the look and feel of this building, to expose as much of the timber as possible and really make it part of the experience.

Amir of Shop from Lloyd Alter on Vimeo.

The tallest building on the boards in North America is a proposed residence at the University of British Columbia. At 53 meters (174 feet) it will just squeak in as the tallest plyscraper.

The structure is comprised of a one storey concrete podium and two concrete cores that support 17 storeys of mass timber and concrete structure. Vertical loads are carried by the timber structure while the two concrete cores provide lateral stability.

I wondered at first about the architecture; it looks like every international style apartment building that went up in Toronto in the sixties and seventies. Turns out thats a feature, not a bug. "To comply with university planning requirements the design reflects the character of International style modernist buildings on the campus." More: World's tallest timber tower to be built in British Columbia

The Pecha Kucha format that limits you to twenty slides is hard; as Blaise Pascal said about writing a letter, "I would have written a shorter letter, but I did not have the time." Really, I could go on for days; the slideshow for my students that this is based on had 150 of them. I have limited this to North American examples because things are finally happening here, from the small projects like Susan Jones' house shown above, to the giant towers. But the real change is coming as taller wood buildings take over the main streets of our cities, where the economy and speed of wood delivers affordable housing faster. This will change everything. More in this Pecha Kucha lecture series: Why small is the new green Counter Intelligence: What's the right choice for a kitchen counter? What is sustainable design? A look at how Australian architect Andrew Maynard does it Green roofs, living walls and vertical farms are all morphing into living green buildings