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Research suggests a wooden future for skyscrapers

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July 2, 2013

Could Berg C.F. Møller's vision prove a blueprint for getting the wooden skyscraper right?...

Could Berg C.F. Møller's vision prove a blueprint for getting the wooden skyscraper right? (Image: Berg C.F. Møller)

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Skyscrapers dominate the skylines of our major cities, offering more urban density and greater flexibility than smaller buildings. However, concrete- and steel-based tall structures require huge amounts of energy for their construction, which comes at a significant environmental cost. This can be mitigated by incorporating technologies such as solar power, passive cooling systems and efficient lighting into the design, but what if we could go even further and build skyscrapers using sustainable materials? Herein lies the impetus behind recent research into the efficacy of wooden skyscrapers.

Before considering the technical hurdles of constructing tall buildings from wood, perhaps the first question which should be asked is: what are the specific benefits wood can offer over concrete and steel?

Sustainability, writ large

The single most compelling argument in favor of building wooden skyscrapers is the fact that, providing the timber is sourced responsibly, they represent an opportunity to create a sustainable building on a truly grand scale, cutting down on overall CO2 output as a result.

As a recent lengthy report on the subject by Michael Green Architects (MGA) entitled "Tall Wood" [PDF] asserts:

Over the last twenty years, as the world’s understanding of anthropogenic climate change has evolved, we have seen the large impact that buildings contribute to the greenhouse gases causing climate change. Concrete production represents roughly 5 percent of world carbon dioxide emissions, the dominant greenhouse gas. In essence the production and transportation of concrete represents more than 5 times the carbon footprint of the airline industry as a whole. It is clear that the very fundamentals of what materials we build our buildings with are worth re-evaluating.

The "Timber Towers" [PDF] report produced by Skidmore, Owings & Merrill (SOM) cites the potential to compete with reinforced concrete and steel, while reducing the carbon footprint by 60 to 75 percent.

About those technical hurdles …

Structural strength

Research suggests a wooden future for skyscrapers

To cope with the heavy load, stresses, and vibrations a skyscraper undergoes daily, it needs to be built from material far more durable than normal timber. The SOM and MGA reports both agree that the solution to constructing tall buildings from wood rests on the use of "Mass Timber."

SOM's report defines Mass Timber as solid panels of wood, engineered for greater strength through the lamination of different layers. These panels can range up to a size of 64 x 8 feet (20 x 2.4 m), and a thickness of a few inches, to 16 inches (40 cm), or in some cases even more.

SOM's researchers prefer to add concrete connecting joints when building with Mass Timber, while MGA utilizes steel to reinforce the mass timber panels. Whichever reinforcing method is chosen, the result is a very tough building material which is worlds away from the timber framing used to build many homes, and suitable for tall buildings up to 30 stories in height, even in high seismic areas like Vancouver.

Indeed, MGA reports that in a weight-to-strength ratio, engineered wood products can often match, and in some cases even exceed, the performance of reinforced concrete.

Fire

If the thought of a very tall building constructed from wood gives you fire-filled nightmares, then you're not alone. Fire is perhaps the single biggest hurdle concerning the widespread adoption of wood as a building material for skyscrapers.

However, according to MGA, the implementation of fire safety measures such as automatic sprinkler protection, sophisticated alarms and smoke control, in addition to treatment of the wood itself, should enable a wooden skyscraper to be relatively safe in a fire scenario.

Gizmag spoke with a representative of the reThink Wood initiative, who explained that if combustion of the wooden structure does occur, its heavy mass ensures that the wood chars at a slow and predictable rate. This helps protect the wood from further degradation, maintains the structural integrity of the building, and reduces its fuel contribution to the fire, which in turn lessens the fire’s heat and flame propagation.

The wood could also be "encapsulated" in gypsum board to retard the spread of fire even further.

The reThink rep also told us that some wood products, such as the large beams used in heavy timber construction and cross laminated timber (CLT), may even perform better in a fire situation than non-combustible materials such as steel and concrete, under certain conditions.

Here we stumble into another hurdle, though. Even if the fire question is satisfactorily answered, most building codes don't allow tall buildings to be constructed from "combustible material," and part of the challenge facing proponents of wooden skyscrapers will be to seek to redefine these codes.

Cost

According to the best projections by MGA, wooden skyscrapers could be built for either the same cost as, or a sum comparatively close to, their concrete and steel brethren. Including the encapsulation method (the most expensive projected model), a hypothetical wooden skyscraper based in Vancouver was projected to cost US$300 per sq ft (roughly $3000 per sq m) for a wooden structure, as opposed to $292 sq ft for a concrete and steel structure.

The future is (almost) here

The residential building will pair wooden construction with sustainable technologies (Imag...

Architectural companies are beginning to wake up to the promise of wooden tall buildings, and Swedish firm Berg C.F. Møller is just one recent example of this. The company has proposed a 34-story wooden skyscraper for HSB Stockholm's architectural competition.

Berg C.F. Møller's residential building will pair wooden construction with sustainable technologies, which includes an energy-saving, glass-covered veranda for every apartment. Solar panels on the roof will satisfy some of the building's power needs, while a communal winter garden will provide residents with an opportunity to grow their own vegetables.

Could Berg C.F. Møller's vision prove a viable blueprint for getting the wooden skyscraper right? It's still too early to tell at this stage in the proposal's development.

One point on which we can be relatively sure though, the emergence of wooden skyscrapers is beginning to look increasingly likely. It now appears to be more a case of not if, but when, they will appear in our cities.

Sources: MGA, SOM, reThink Wood, Berg C.F. Møller

About the Author
Adam Williams Adam scours the globe from his home in North Wales in order to bring the best of innovative architecture and sustainable design to the pages of Gizmag. Most of his spare time is spent dabbling in music, tinkering with old Macintosh computers and trying to keep his even older VW bus on the road.

  All articles by Adam Williams
23 Comments

What about hemp, bamboo and coconut fiber? I would guess that incorporating these in the right ways would greatly improve both the strength and environmental impact (as in how good it is).

Ben Tumaru O'Brien
2nd July, 2013 @ 01:06 pm PDT

What about longevity? Weathering and other concerns. I would have some concern over structural members that might fail at a given time later on. Much less how a wooden skyscraper might perform in high wind.

Not saying it can't be done. I just want to make sure it's safe.

VoiceofReason
2nd July, 2013 @ 03:49 pm PDT

@VoiceofReason i would think that wood probably has better longevity than concrete, which is susceptible to concrete cancer. There are plenty of wooden buildings around that are 400+ years old, i don't know how safe our concrete structures will be after half that time.

inchiki
2nd July, 2013 @ 06:57 pm PDT

A great technical leap, just need to lower the weight/strength ratio

Ricky Hall
2nd July, 2013 @ 09:25 pm PDT

re; inchiki

It is not just wood there is also the glue.

There are concrete structures that the Romans built that are still in use. The rebar on the other hand might be a problem.

Slowburn
2nd July, 2013 @ 10:16 pm PDT

You may want to check this, made using X-Lam technology (wood only), which resisted to many repeated huge seisimc tests without significant damages: http://www.ivalsa.cnr.it/foto-e-video/video/progetto-sofie-test-sismico-ottobre-2007.html

Mario Maio
2nd July, 2013 @ 11:18 pm PDT

Ahhh..does the word TERMITE mean anything to you guys....?

Arnold Stonehouse
3rd July, 2013 @ 07:10 am PDT

Rebar made from basalt is immune to rust, and a barrier to "concrete cancer". Basalt is also as fireproof as asbestos, without the environmental concerns, and can be used as an alternative to fiberglass insulation. Panels incorporating basalt are inherently fireproof and durable, so it seems a natural partner to wood structures.

Pat Kelley
3rd July, 2013 @ 09:30 am PDT

Some 55 years ago Mies noted that highrises were more economical to build than townhouses. That actually means that they provided HUGELY LESS ENERGY to build.

And the problem of acoustic privacy remains but has now been solved with the availability of AAC.

The ledger beams appear to be too shallow.

The Design and renderings are beautiful but, in reality, this is a specious effort.

Bill

Lewis M. Dickens III
3rd July, 2013 @ 09:38 am PDT

After building a three story house in Colorado, I was impressed by the compression forces of the mostly wooden structure. Sheetrock cracked which we had to repair constantly as the house "settled in". After 10 years, I bet the house compressed down about from an eighth to a quarter of an inch. "No, I did not take a height reading at the initial frame out. Wish I had."

I have read of such things on huge log homes, where there are mechanical jacks to set the home level. I can only imagine at the amount of "settle in" on such a tall wooden structure.

lwesson
3rd July, 2013 @ 11:10 am PDT

Log homes would be subjected to normal shrinkage. Engineered wood structure does not have a significant problem of shrinkage -- because it is engineered not to.

Thom DelForge
3rd July, 2013 @ 12:28 pm PDT

Wood is good if there would be enough wood for the whole world to build sky scrapper filled cities. Strong wood comes from trees which lived long. Use of wood for sky scrappers would eliminate large trees at an alarming rate, faster than that is happening now in Brazil and other developing countries. Use of these large trees also would mean reduction in carbon dioxide to oxygen conversion by photosynthesis.

May be it is time to consider plastics made from cheap shale gas (natural gas) for producing large scale plastics which can be reinforced with natural fibers, such as hemp mentioned in one of the earlier comments. Let the trees survive. They will take away the CO2 generated in plastics production.

Babu
3rd July, 2013 @ 12:57 pm PDT

re; lwesson

Whoever framed the house did a terrible job.

Slowburn
3rd July, 2013 @ 01:23 pm PDT

Wood VS Steel in a fire.

Steel will soften and bend at temperatures well below its melting point.

Unburnt wood should retain much of its stiffness while the outer part burns.

The WTC collapsed because the steel at the floors on fire got hot enough to bend, not melt. The high speed collapse was due to the same effect used by martial arts demonstrators to break tall stacks of boards or blocks of concrete or ice.

The trick is the spacers between the blocks. All the person has to do is be able to break the first block and not hold back. The space allows the block to accelerate and transfer force to the second block. The mass of downward accelerating broken blocks continuously increases, increasing the speed of the break.

The same physical phenomena happened with the WTC. The steel got hot enough to soften and bend, dropping all the weight of the part above the fire very quickly. The structure of the floor immediately below could not handle the impact, it failed and everything hit the next floor and the next, cascading down, gaining speed as more and more mass was added punching down with each collapsing floor.

The only thing that could have prevented the WTC collapse would have been to use something other than steel, with a *softening* temperature of 2,000+ degrees Fahrenheit. Nothing such suitable for a skyscraper frame existed in the 1970's and I bet there still isn't.

The design of the WTC also contributed to its collapse. The towers' outer faces were the main supporting elements. The central core with the elevators was pretty much self supporting. The floors were hung between the outer face and the central core. There was *nothing* supporting floor to floor, every floor was designed so it could be completely open if the renter wanted it that way. All interior walls were non load bearing. The design was "perfect" for exactly the type of failure from fire that they experienced.

Dividing every floor into quadrants, with solid, floor to floor, load bearing walls all the way up *might* have prevented their collapse. The debris from the impacts wouldn't have been able to punch completely through. The solid elevator core partially prevented that in the first tower hit. The second one dropped first because it was hit lower down and off center. The fire was spread wider and there was more building above the fire - thus the steel framing didn't have to get as hot before it reached its bending failure point.

Another contributor was the fire wasn't from just burning jet fuel. There was all the office furniture, plastic housings of office equipment, carpets, and a large number of filing cabinets full of paper. Wouldn't matter how 'fire resistant' any of that was, soaked in burning jet fuel it would burn.

Of course the conspiracy idiots will ignore any such physical science facts and continue to insist that somehow a few tons of demolition explosives were placed throughout the buildings without anyone noticing.

Gregg Eshelman
3rd July, 2013 @ 01:49 pm PDT

Hemp composites is the way to go.

ezeflyer
3rd July, 2013 @ 02:01 pm PDT

Ladies & Gentlemen,

The answer you are all seeking already exists and we are in the process of preparing to use it in our pending transformational method of construction to bring construction out of the 18th century. The AEWC Research Program at the University of Maine has developed a method of taking waste raw agricultural fibers – including wood – and turning them into structural members that are much stronger than raw wood and have the colors ingrained eliminating the need for painting. Among their many current applications, they are currently being used by the Coast Guard as bulkheads to resist the salt water, boats and ice flows banging against them. I was privileged to see their testing before our army put them to work in Afghanistan as shields to protect our military as well as their testing for use as bridge beams. Yes, I saw the equivalent of fully loaded cement trucks rumbling over the beams. 2 ½ weeks of this test is equal to a 50 year life. Instead of twisting and bending, these components come with 0.002th of an inch accuracy in the exact shapes we want. They are not food for water or termites and cost far less than any other form of structural component we have yet to discover.

Using this as structural components, tests on our transformational construction system (we are projected to do to construction what Henry Ford did to the automobile) showed that a purposely mis-configured structure will withstand a 150# snow load; during a 200 mph wind; during a seismic 7 earthquake. Fire will not affect our system. It is Cradle-2-Cradle ~ reconfigurable by the occupants to meet their current needs. So, after a flood, the building can be disassembled, cleaned and dried and then reassembled without damage except to the contents of the occupant.

The Chinese recently erected a 30 story hotel ready for occupancy in 15 days that is engineered to withstand a seismic 9 earthquake. Chinese officials recently had a meeting with us regarding using our transformational construction system in conjunction with that system in the construction of their pending Eco-Small Towns (1.5 to 2 million occupants each) with 200 story towers. These totally encapsulated cities are being design/engineered by American firms and are very attractive. Having been in a predecessor, I would like to live in one. Among their many goals, is to have these totally new cities not need automobiles and be far more environment-friendly than anything under construction today. Another is to produce 300 Million new housing units in totally new cities in the next quarter century. For the good of the environment, they are seeking leading-edge materials, renewable energy and construction systems. Imagine if instead, wood, steel and concrete were used for this massive undertaking what it would do to Mother Earth.

Technotard

technotard
3rd July, 2013 @ 07:22 pm PDT

What ever happened to the big breakthrough in concrete? I read they had tweaked the formula of Portland cement and increased the strength 5 times. Was it Grancrete?

Don Duncan
3rd July, 2013 @ 08:04 pm PDT

re; Gregg Eshelman

The WTC towers probably would not have collapsed had the heat shielding on the steel not been stripped off by the moving debris or had there been fire sprinklers.

re; technotard

The Chinese also have had brand new building just fall over.

Slowburn
3rd July, 2013 @ 10:31 pm PDT

@Gregg Eshelman

Add to that the rhythmic pounding of thousand of feet from the people going down stairs, even if it's in the central core of the structure.

nulo
4th July, 2013 @ 01:30 am PDT

Better yet: Hempcrete.

Rick Steeb
4th July, 2013 @ 06:52 am PDT

Fiber filled concrete is reinforced even if it does not have rebar. I prefer monofilaments.

We could do as the Romans and design structures that do not need the reinforcements in the concrete.

Slowburn
4th July, 2013 @ 11:53 pm PDT

As a firefighter, give me a well engineered building that isn't ridiculously tall and is made out of inherently fire resistant materials. It is all well and good trying to clad materials we normally regard as "fuel" to make them perform, and set up policies to improve how they are handled and installed but these are subject to people at a later date who do not understand how these things are part of an overall design.

Give these designers a "kick up the pants" from me please and ask them to think about how they'd like to be entering into such a building to start fighting a fire on the tenth floor after it's been going for an hour.

Please think about sprinklers, though, in all your designs - they save lives!

999 HOT
16th July, 2013 @ 03:17 pm PDT

oh what rot.

noteugene
17th July, 2013 @ 04:27 pm PDT
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