Hey all, this post has been bouncing around in my head awhile so I thought I'd take this lazy Saturday to write it down, and maybe start a discussion about timber, sustainability, and greenwashing in marketing.
The word "sustainable" is often used in the marketing material of buildings these days, especially in timber highrises that have been cropping up lately. But is the choice of timber over steel or concrete really more sustainable?
There have been dozens of research papers comparing cross-laminated timber (CLT) and glue-laminated timber (glulam) in comparison to steel and concrete used in buildings of equivalent form and function to determine relative environmental impact in terms of greenhouse gasses, acidification, smog, and other metrics. The majority arrive at the same answer: yes, but...
Assuming the use phases of the two building structures are functionally equivalent (same energy consumption, same water use), the impact of the building is heavily dependent on transportation of the material to the jobsite. Believe it or not, the overwhelming majority of a building's carbon footprint (neglecting resource use during the service life) is embodied in fuel burned to transport material and construct the building. In comparison, the energy of raw material extraction, processing, and manufacture is almost negligible.
The chief obstacle of CLT and glulam becoming the most sustainable structural materials is availability. Timber quickly becomes the less sustainable option the further the manufacturing plant is from the jobsite, and concrete and steel are far more relatively available. This is particularly a problem in the United States, where there are only two reputable CLT manufacturers in the entire country capable of producing high volumes of product. If your project is in Washington or Oregon, engineered timber structures might be more sustainable. If it's anywhere else in the US, timber is probably worse.
Bottom line: timber structures are only the sustainable option if the material is sourced locally, or at least from the same distance as the nearest concrete plant.
P.S. This post ignores forest maintenance that would be required if timber becomes widely available; that's a whole other can of worms.
I actually had to google timber highrise. Oh PNW, always up to something goofy. But it does sound like it could be a really cool regional niche. There are far too many factors to list preventing this from happening in other markets. Primary question would be "Why?".
Whenever I hear of ground concrete etc, I think of the beach at Tommy Thompson Park in Toronto. Much of the material from buiding demolition is dumped there. They're taking advantage of seiches to break down the material over time- to make a beach.
Random - possibly. But there are many chemicals used to fuse the concrete and as of now it's much more expensive to reuse than to continue mining sand. I always figured the most viable alternative would be to find a way to use finer sands such as those found in the ever expanding deserts. That kind of sand hasn't been used for concrete but it's made long lasting adobe structures for years. Maybe there's something to that.
Aug 5, 17 10:02 pm ·
·
randomised
Maybe rammed earth will finally really take off. There's this rammed earth and concrete watchtower in NL. Quite allright:
Random - that would be a great alternative. The trick is getting that to work at a skyscraper level. I haven't seen any rammed earth or other soft sands used over maybe 4 stories. Nothing in the double digits in terms of floors. But maybe there's a precedent out there. Surely some combo of steel and chemical engineering could make it feasible to construct a tower that way.
Nothing is "sustainable" really. What if the builder of that sustainable CLT-tower eats a hamburger for lunch, made with Brazilian beef of cows that were fed soy that was grown on farmland created by chopping down the rainforest. Is it still sustainable? And if the structural engineer needs computers made with precious metal parts that were sourced under polluting circumstances using child labour and the computer servers that are hosting the data need airconditioning and are powered by a coal burning electricity plant, is it still sustainable? Etc.
Aug 6, 17 3:20 pm ·
·
citizen
^ Bingo. Define "truly sustainable." Or, better, use more precise, less squishy terms.
Alan Organski gave a convincing argument in favor of wood in a presentation I saw (http://timbercity.org/).
Aug 6, 17 3:47 pm ·
·
randomised
He must make convincing case, looking at your nom de plume :)
Aug 7, 17 12:12 am ·
·
Wood Guy
Ha, yeah, I didn't think of that. I'm not convinced that CLT is the answer to all of our problems; I think that beyond-organic agriculture, regenerative architecture and population control are closer to the right answer, if the question is how do we provide a livable planet for future generations. But Organski's architecture and presentation are thoughtful and elegant.
Agreed. The only sustainable human cultures were destroyed by "civilized" ones. Sending Musk and his ilk to Mars would be the first step of the corrective process.
Excellent thread, Schoon! I'm fascinated by CLT and high rise timber but admittedly know little about it. IKD is doing a CLT installation for the Exhibit Columbus Miller Prize and I'm really looking forward to it. They are specifically addressing underutilized Indiana hardwoods in their project, so the delivery distance I ant and problem.
It seems to make sense (anecdotally, not data) that more sustainably-grown and-harvested timber would be better overall than continued extraction for steel and, as archinine pointed out, we're running out of sand.
Running out of sand, and the energy it takes to convert rock to Portland cement is enormous. Using sustainably harvested wood (a relatively precise term in the timber management world) sequesters the carbon stored in that wood, and allows new growth to sequester more carbon. I'm not convinced that skyscrapers are the answer at all, and when I've looked into using CLT for residential work the costs don't work out at all, but it's worth considering the argument for materials other than concrete and steel.
One would assume as the costs rise for sand/concrete, market forces will cause timber to be the de facto method of choice whenever possible - whether that includes skyscrapers proper is to be seen. It's unfortunate that nonrenewable resources tend to need to be almost wiped out before any changes happen, but this is similar to what we've seen with coal-oil-gas moving to solar-hydro. Because, you know capitalism.
randomized, a professor of mine once said "the most sustainable thing to build as a developer is nothing. The next most sustainable option is to renovate. If neither of these suffice, build green."
Wood Guy, carbon sequestration is factored into some studies and does make a significant impact, often resulting in net negative CO2 emissions! However there are other environmental problems not alleviated by carbon sequestration, for example NOX released in significant quantities during the processing of the adhesive that binds the lumber together in CLT and glulam.
Also, the thing about steel is that it's the most recycled building materials (at a rate between 66-80%), and its emissions in the production stage are often discounted in studies by a certain percent to account for use of recycled steel. However as mentioned earlier, energy of production is dwarfed by the energy needed to transport the material.
This chart includes energy of raw material acquisition, material processing, transport and construction, and another set with transport and construction removed to show just how significant the diesel energy is in those phases. Energy used during service life is assumed to be the same and therefore omitted, but in reality slight R-value differences might influence the heating/cooling energy of the two structures.
This stuff is fascinating to me and I highly recommend checking out the CLT handbook (a quick google and you should find it) if you're interested in these materials.
EDIT: Actually I'll just link it here for convenience.
Bulk carriers, tankers, and container ships consume between 150-225 tons of bunker fuel per day. There are about 40,000 ships in these classes. That's an average of close to 8m tons of fuel burned ever day.
Aug 7, 17 10:27 am ·
·
Wood Guy
Schoon, I know that studies show carbon sequestration, I just don't believe they fully account for what really happens in a healthy forest if the wood is allowed to rot. The studies typically say that rotting wood releases the same CO2 as burning it, but they don't account for how forest ecology really works, with other trees taking up the carbon from the rotting tree, mycorrhizal action, etc. The forests the trees for CLT come from (in the east, usually Nordic in Quebec, which has millions of acres of black spruce monoculture, "sustainably" harvested on a 40-year cycle, but not what I would call a healthy forest, as no monoculture is healthy (or truly sustainable). The Alan Organski presentation I linked to above goes into detail about the potential for negative COs emissions, and uses a forest close to me as the theoretical source. I have about 60 acres of tree farm so it's an area I am interested in.
Additionally, concrete can be made much more green by including 50% pozzolan or steel slag, which also reduces the environmental impact of the steel.
Aug 7, 17 10:51 am ·
·
randomised
Also, you can add olivine as aggregate to concrete, actually 'capturing' CO2 out of the air. Some companies have even managed, at least on paper I believe, to at least balance the CO2 emissions of the production and perhaps 'capture' even more so reduce the amount of CO2 in the atmosphere, hypothetically.
Wood Guy, I just skimmed the study from the link you posted, looks interesting. I'll have to take an afternoon sometime to read it thoroughly. I dipped my toes into forest ecology while researching life-cycle assessments of CLT, it seems like a very fascinating field.
Miles, it seems that we can try to narrow the emissions and energy use of our buildings as much as we can, but the bulk of the problem always traces back to areas of wider concern, which we often can't control from within our industry. If we vow to use 100% recycled steel, it doesn't matter if we can only afford steel shipped from across the ocean. Even if we have an entirely electric transport system someday, it won't make a difference if the grid is powered by coal and gas.
That's why I'm a fan of locally sustainable communities. But such decentralization is impossible not in the least because it violates every principle of modern economics and control.
Here in paradise we have minimum sf requirements designed to "protect" property value but that only serves to destroy sustainability in many ways from energy and resource usage to exclusionary zoning and unaffordable housing. Not to mention that nearly every house that is sold is razed to make room for an even larger and less sustainable one - that can be sold for even more money, of course.
Two houses around the corner from me were razed in the last two weeks. Both were simple ranches that could have easily and nicely been updated. Both will be developed to the maximum extent of the property if not beyond by variance, as the local Candy Store (ZBA) has set a precedent that not being able to maximize profit is a hardship that trumps zoning.
Here in paradise we have a 'luxury tax' on house sales over $1m (pretty much everything). Common practice for developers is to negoiate occupancy before closing by paying in full. Once in occupancy they raze any buildings so that only vacant land transfers, thereby avoiding the tax.
You should probably read On Architecture by Frank Lloyd Wright. If you have, reread it. Then read Lewis Mumford's The City in History. Then reread them every year for the rest of your life.
I think living in tandem with nature is essential for many. However, if you fear technology you miss out on its benefits.
Aug 8, 17 12:28 pm ·
·
BIMBlaster
Yes, architecture as an industry composite fears technology, if that is what you mean. FLW's "prophecy" was all skyscrapers will crumble, even if he designed a couple he was still honest that the current state sustainability model is unrealistic over time.
Here is the Pons Fabricius bridge in Rome that was built in 62 BC and has been in service ever since. It is not made of wood. Would this be "sustainable" enough or not?
Volunteer makes an excellent point - are life cycle costs including in any of these analyses?
How many buildings of any type are demolished well short of their functional life span?
Aug 9, 17 7:44 am ·
·
Schoon
Miles, life-cycle costs are the bases of these analyses, typically called "Life Cycle Assessments." The life cycle of a building is typically tracked as: Raw material extraction -> Material processing -> transportation of material and construction of building -> service life (usually assumed as 60 years) and maintenance -> demolition and material disposal. The environmental "costs" are inventoried for each stage in the life cycle. It sounds simple, but there's a lot of uncertainty over what to include in the inventory and what to discount based on shared processes, recycled material, etc.
Aug 9, 17 8:21 am ·
·
Schoon
Also, you and Volunteer are right to question the lifespan assumption. Absolutely don't take these studies as gospel - they're all built on assumptions and it's important to know what those assumptions are if you want to use the conclusions of a study to motivate a decision.
I've been following this from a far... on account of being on vacation and all... but I recently participated in a presentation by the architect for the following project... the first of it's kind I'm told.
Although interesting in many ways, the application of such building techniques are impracticable on the larger scale and allow very little design flexibility. Plus you have the added bonus of having to educate the city officials.
Fun fact ... they didn't really, but local code hadn't caught up with the whole 'char rate' argument yet, so they picked the option requiring less brain damage.
Aug 9, 17 12:22 pm ·
·
Non Sequitur
Correct, I do remember that. I also remember that since the columns would be covered, the savings by using less attractive wood equalled close to the cost of gypsum.
Likely true ... where labour factors in to that is a bit of a ? ... its certainly not too fast to lay 4 layers of drywall around an entire building and terminate all connections nicely (especially if you are having some exposed timber on the panels, for instance).
Are Timber Towers Truly Sustainable?
Hey all, this post has been bouncing around in my head awhile so I thought I'd take this lazy Saturday to write it down, and maybe start a discussion about timber, sustainability, and greenwashing in marketing.
The word "sustainable" is often used in the marketing material of buildings these days, especially in timber highrises that have been cropping up lately. But is the choice of timber over steel or concrete really more sustainable?
There have been dozens of research papers comparing cross-laminated timber (CLT) and glue-laminated timber (glulam) in comparison to steel and concrete used in buildings of equivalent form and function to determine relative environmental impact in terms of greenhouse gasses, acidification, smog, and other metrics. The majority arrive at the same answer: yes, but...
Assuming the use phases of the two building structures are functionally equivalent (same energy consumption, same water use), the impact of the building is heavily dependent on transportation of the material to the jobsite. Believe it or not, the overwhelming majority of a building's carbon footprint (neglecting resource use during the service life) is embodied in fuel burned to transport material and construct the building. In comparison, the energy of raw material extraction, processing, and manufacture is almost negligible.
The chief obstacle of CLT and glulam becoming the most sustainable structural materials is availability. Timber quickly becomes the less sustainable option the further the manufacturing plant is from the jobsite, and concrete and steel are far more relatively available. This is particularly a problem in the United States, where there are only two reputable CLT manufacturers in the entire country capable of producing high volumes of product. If your project is in Washington or Oregon, engineered timber structures might be more sustainable. If it's anywhere else in the US, timber is probably worse.
Bottom line: timber structures are only the sustainable option if the material is sourced locally, or at least from the same distance as the nearest concrete plant.
P.S. This post ignores forest maintenance that would be required if timber becomes widely available; that's a whole other can of worms.
Most steel comes from China.
A very good point. Many Life Cycle models assume the material is sourced from the nearest plant, but often market forces dictate otherwise.
I actually had to google timber highrise. Oh PNW, always up to something goofy. But it does sound like it could be a really cool regional niche. There are far too many factors to list preventing this from happening in other markets. Primary question would be "Why?".
The wood is renewable - as far as I understand, the concrete/steel is not.
Very true. We should be looking for alternative fine aggregates.
Grinded concrete, bricks or ceramics from demolished buildings might become an affordable alternative.
Whenever I hear of ground concrete etc, I think of the beach at Tommy Thompson Park in Toronto. Much of the material from buiding demolition is dumped there. They're taking advantage of seiches to break down the material over time- to make a beach.
But what if the transport of the timber is done by sailing boat?
Build the boat with timber, then reuse the timber to erect the building.
Miles, that's just way old school.
I resemble that remark.
"Build the boat with timber, then reuse the timber to erect the building." I like it--the Ox-Cart Man approach.
better yet, just live on a boat.
But do they stack into a high-rise, A High-rise of Boats James Wines would call it, that's the $64000 question!
One is free on a boat. For a time.
Maybe rammed earth will finally really take off. There's this rammed earth and concrete watchtower in NL. Quite allright:
https://www.dezeen.com/2017/05...
Nothing is "sustainable" really. What if the builder of that sustainable CLT-tower eats a hamburger for lunch, made with Brazilian beef of cows that were fed soy that was grown on farmland created by chopping down the rainforest. Is it still sustainable? And if the structural engineer needs computers made with precious metal parts that were sourced under polluting circumstances using child labour and the computer servers that are hosting the data need airconditioning and are powered by a coal burning electricity plant, is it still sustainable? Etc.
^ Bingo. Define "truly sustainable." Or, better, use more precise, less squishy terms.
Alan Organski gave a convincing argument in favor of wood in a presentation I saw (http://timbercity.org/).
He must make convincing case, looking at your nom de plume :)
Ha, yeah, I didn't think of that. I'm not convinced that CLT is the answer to all of our problems; I think that beyond-organic agriculture, regenerative architecture and population control are closer to the right answer, if the question is how do we provide a livable planet for future generations. But Organski's architecture and presentation are thoughtful and elegant.
Agreed. The only sustainable human cultures were destroyed by "civilized" ones. Sending Musk and his ilk to Mars would be the first step of the corrective process.
It seems to make sense (anecdotally, not data) that more sustainably-grown and-harvested timber would be better overall than continued extraction for steel and, as archinine pointed out, we're running out of sand.
Posting from a phone: the above should say "...delivery distance isn't a problem."
Running out of sand, and the energy it takes to convert rock to Portland cement is enormous. Using sustainably harvested wood (a relatively precise term in the timber management world) sequesters the carbon stored in that wood, and allows new growth to sequester more carbon. I'm not convinced that skyscrapers are the answer at all, and when I've looked into using CLT for residential work the costs don't work out at all, but it's worth considering the argument for materials other than concrete and steel.
randomized, a professor of mine once said "the most sustainable thing to build as a developer is nothing. The next most sustainable option is to renovate. If neither of these suffice, build green."
Wood Guy, carbon sequestration is factored into some studies and does make a significant impact, often resulting in net negative CO2 emissions! However there are other environmental problems not alleviated by carbon sequestration, for example NOX released in significant quantities during the processing of the adhesive that binds the lumber together in CLT and glulam.
Also, the thing about steel is that it's the most recycled building materials (at a rate between 66-80%), and its emissions in the production stage are often discounted in studies by a certain percent to account for use of recycled steel. However as mentioned earlier, energy of production is dwarfed by the energy needed to transport the material.
This chart includes energy of raw material acquisition, material processing, transport and construction, and another set with transport and construction removed to show just how significant the diesel energy is in those phases. Energy used during service life is assumed to be the same and therefore omitted, but in reality slight R-value differences might influence the heating/cooling energy of the two structures.
This stuff is fascinating to me and I highly recommend checking out the CLT handbook (a quick google and you should find it) if you're interested in these materials.
EDIT: Actually I'll just link it here for convenience.
Bulk carriers, tankers, and container ships consume between 150-225 tons of bunker fuel per day. There are about 40,000 ships in these classes. That's an average of close to 8m tons of fuel burned ever day.
Schoon, I know that studies show carbon sequestration, I just don't believe they fully account for what really happens in a healthy forest if the wood is allowed to rot. The studies typically say that rotting wood releases the same CO2 as burning it, but they don't account for how forest ecology really works, with other trees taking up the carbon from the rotting tree, mycorrhizal action, etc. The forests the trees for CLT come from (in the east, usually Nordic in Quebec, which has millions of acres of black spruce monoculture, "sustainably" harvested on a 40-year cycle, but not what I would call a healthy forest, as no monoculture is healthy (or truly sustainable). The Alan Organski presentation I linked to above goes into detail about the potential for negative COs emissions, and uses a forest close to me as the theoretical source. I have about 60 acres of tree farm so it's an area I am interested in.
Additionally, concrete can be made much more green by including 50% pozzolan or steel slag, which also reduces the environmental impact of the steel.
Also, you can add olivine as aggregate to concrete, actually 'capturing' CO2 out of the air. Some companies have even managed, at least on paper I believe, to at least balance the CO2 emissions of the production and perhaps 'capture' even more so reduce the amount of CO2 in the atmosphere, hypothetically.
Actually, I'd advice against building green, it's toxic: http://www.nytimes.com/2010/04/05/arts/05iht-design5.html
Wood Guy, I just skimmed the study from the link you posted, looks interesting. I'll have to take an afternoon sometime to read it thoroughly. I dipped my toes into forest ecology while researching life-cycle assessments of CLT, it seems like a very fascinating field.
Miles, it seems that we can try to narrow the emissions and energy use of our buildings as much as we can, but the bulk of the problem always traces back to areas of wider concern, which we often can't control from within our industry. If we vow to use 100% recycled steel, it doesn't matter if we can only afford steel shipped from across the ocean. Even if we have an entirely electric transport system someday, it won't make a difference if the grid is powered by coal and gas.
That's why I'm a fan of locally sustainable communities. But such decentralization is impossible not in the least because it violates every principle of modern economics and control.
Here in paradise we have minimum sf requirements designed to "protect" property value but that only serves to destroy sustainability in many ways from energy and resource usage to exclusionary zoning and unaffordable housing. Not to mention that nearly every house that is sold is razed to make room for an even larger and less sustainable one - that can be sold for even more money, of course.
Two houses around the corner from me were razed in the last two weeks. Both were simple ranches that could have easily and nicely been updated. Both will be developed to the maximum extent of the property if not beyond by variance, as the local Candy Store (ZBA) has set a precedent that not being able to maximize profit is a hardship that trumps zoning.
"...as the local Candy Store (ZBA) has set a precedent that not being able to maximize profit is a hardship that trumps zoning."
:o
What the fuuuuuuck?
Sadly, I understand every word, even the ironic ones.
Here in paradise we have a 'luxury tax' on house sales over $1m (pretty much everything). Common practice for developers is to negoiate occupancy before closing by paying in full. Once in occupancy they raze any buildings so that only vacant land transfers, thereby avoiding the tax.
You should probably read On Architecture by Frank Lloyd Wright. If you have, reread it. Then read Lewis Mumford's The City in History. Then reread them every year for the rest of your life.
Then read Ezekiel chapter 47.
What goes up...
...can stay up if you hire a structural engineer.
BIMBlaster, keep in mind FLW also wrote this.
I think living in tandem with nature is essential for many. However, if you fear technology you miss out on its benefits.
Yes, architecture as an industry composite fears technology, if that is what you mean. FLW's "prophecy" was all skyscrapers will crumble, even if he designed a couple he was still honest that the current state sustainability model is unrealistic over time.
FLW was an architect of words but that doesn't get much credit.
I'm sure I've seen some of his drawings laying about, like hanging framed on the walls of MoMA, but maybe I'm mistaken
Here is the Pons Fabricius bridge in Rome that was built in 62 BC and has been in service ever since. It is not made of wood. Would this be "sustainable" enough or not?
Volunteer makes an excellent point - are life cycle costs including in any of these analyses?
How many buildings of any type are demolished well short of their functional life span?
Miles, life-cycle costs are the bases of these analyses, typically called "Life Cycle Assessments." The life cycle of a building is typically tracked as: Raw material extraction -> Material processing -> transportation of material and construction of building -> service life (usually assumed as 60 years) and maintenance -> demolition and material disposal. The environmental "costs" are inventoried for each stage in the life cycle. It sounds simple, but there's a lot of uncertainty over what to include in the inventory and what to discount based on shared processes, recycled material, etc.
Also, you and Volunteer are right to question the lifespan assumption. Absolutely don't take these studies as gospel - they're all built on assumptions and it's important to know what those assumptions are if you want to use the conclusions of a study to motivate a decision.
I've been following this from a far... on account of being on vacation and all... but I recently participated in a presentation by the architect for the following project... the first of it's kind I'm told.
Although interesting in many ways, the application of such building techniques are impracticable on the larger scale and allow very little design flexibility. Plus you have the added bonus of having to educate the city officials.
Brock Commons
Fun fact, they had to apply 4 layers of gypsum board in order to achieve the required fire rating at the wood columns.
Fun fact ... they didn't really, but local code hadn't caught up with the whole 'char rate' argument yet, so they picked the option requiring less brain damage.
Correct, I do remember that. I also remember that since the columns would be covered, the savings by using less attractive wood equalled close to the cost of gypsum.
Likely true ... where labour factors in to that is a bit of a ? ... its certainly not too fast to lay 4 layers of drywall around an entire building and terminate all connections nicely (especially if you are having some exposed timber on the panels, for instance).
Cool project using "waste" trees won an Architect Mag R&D award this year...http://www.architectmagazine.c...
Block this user
Are you sure you want to block this user and hide all related comments throughout the site?
Archinect
This is your first comment on Archinect. Your comment will be visible once approved.