The Case for Making Cities Out of Wood(nautil.us)
nautil.us
The Case for Making Cities Out of Wood
http://nautil.us/blog/-the-case-for-making-cities-out-of-wood
105 comments
The question I have about all of this is the environmental impact of the "densification of wood." They cite it being similar to paper manufacturing, which is really energy intensive and is a horribly polluting industry.
I don't have any info on the above, but it is something I wonder about.
I don't have any info on the above, but it is something I wonder about.
I'm day dreaming about 'aktivhaus' (sp?) style residential in the desert.
What would that look like?
My starting notion is a three level structure. Bottom is carport, patio, storage. Middle would be kitchen, baths, common areas, study. Upper would be bedroom(s). Maybe a roof top deck.
South wall would have horizontal solar louvres. Kinda like the Burr library in downtown Phoenix.
Roof top solar something. But I'd still want to be able to look up at the stars.
Grey water system of some sort. So the ground level would have a cistern of some sort.
Is wood a viable option for the desert? I know zilch about thermal loads, insulation, etc. If so, how much wood?
What would that look like?
My starting notion is a three level structure. Bottom is carport, patio, storage. Middle would be kitchen, baths, common areas, study. Upper would be bedroom(s). Maybe a roof top deck.
South wall would have horizontal solar louvres. Kinda like the Burr library in downtown Phoenix.
Roof top solar something. But I'd still want to be able to look up at the stars.
Grey water system of some sort. So the ground level would have a cistern of some sort.
Is wood a viable option for the desert? I know zilch about thermal loads, insulation, etc. If so, how much wood?
Some cities were wood, and they burned. My concrete condo is in the burn path of the 'great Ottawa fire'. Wikipedia doesn't have enough pictures, worth googling.
https://en.wikipedia.org/wiki/1900_Hull–Ottawa_fire
https://en.wikipedia.org/wiki/1900_Hull–Ottawa_fire
Tons of major cities have been wiped out from fire in the early 1900's. But you have to consider how ill-equipped they were to handle fire, not to mention a total lack of research. Modern cities have working fire hydrants and buildings can have multiple fire suppression systems. Most of this is due to those massive fires happening.
Here is NIST's report on fire resistance of timber structures (https://www.nist.gov/sites/default/files/documents/el/fire_r...). It includes guidelines that help increase the fire safety of wood buildings. This page (https://www.firechief.com/2017/03/14/are-wood-frame-high-ris...) shows CLT has had testing to approve it for use in 6+ storey buildings in multiple countries.
Here is NIST's report on fire resistance of timber structures (https://www.nist.gov/sites/default/files/documents/el/fire_r...). It includes guidelines that help increase the fire safety of wood buildings. This page (https://www.firechief.com/2017/03/14/are-wood-frame-high-ris...) shows CLT has had testing to approve it for use in 6+ storey buildings in multiple countries.
I'm wondering if 'total collapse of cell walls and the complete densification of the natural wood with highly aligned cellulose nanofibres.' means that stuff isn't going to burn until you get temperatures where steel melts anyway?
It would seem so. from the article:
> Massive wood walls and structural beams and columns comprised of engineered panels have demonstrated fire performance equal to concrete and, in some cases, superior to steel
> Massive wood walls and structural beams and columns comprised of engineered panels have demonstrated fire performance equal to concrete and, in some cases, superior to steel
one big difference seems to be that once the critical point is reached, even if the threshold very high, the wood contributes to the fire and nourishes it, unlike concrete or steal. a skyscraper with proper sprinkling should be fine.
The case against:
https://en.wikipedia.org/wiki/List_of_town_and_city_fires
https://en.wikipedia.org/wiki/List_of_town_and_city_fires
The kind of wood used here does not burn like normal timber. Its treatment gives it strength and fire resistance. There are some large scale tests that need to be done yet, in order to better understand how a fire would behave in a midsized wood building. It's all in the article.
Keep in mind, this is way more testing than usual, lots of other materials have been used in large buildings, sometimes with disastrous consequences (see: Grenfell Tower fire).
Keep in mind, this is way more testing than usual, lots of other materials have been used in large buildings, sometimes with disastrous consequences (see: Grenfell Tower fire).
[deleted]
I think of Chicago first. The wood city that burned and led to the invention of 'skyscrapers'.
The focus of this article is innovation in this space.
What happened in Ottawa or Chicago or Tokyo is relevant in a historical sense but this is about recent innovations that make wood viable (both from a safety/fire-resistant perspective and economical).
What happened in Ottawa or Chicago or Tokyo is relevant in a historical sense but this is about recent innovations that make wood viable (both from a safety/fire-resistant perspective and economical).
I think we all know this, but this article was less-than-convincing and nothing has been deployed at scale yet.
Chicago has a CLT building - the new flagship McDonald's restaurant is CLT and steel.
Additionally, a CLT office building has been approved in Chicago and will be the largest CLT building in the United States when finished.
Additionally, a CLT office building has been approved in Chicago and will be the largest CLT building in the United States when finished.
Emperor Nero likes this element!
Three out of three top comments here are about fires - an issue the article specifically talks about.
How about reading the whole piece instead of just a headline?
How about reading the whole piece instead of just a headline?
> He wants to do many more experiments because it’s still not clear how, in mass timber buildings, to get compartment fires to reliably burn out on their own, a “cornerstone of fire safety engineering design,” he writes.
In this context, the article's later comparison of this wood to concrete seems exaggerated.
In this context, the article's later comparison of this wood to concrete seems exaggerated.
The article does not address the topic in sufficient detail which is why people keep commenting about it.
> How about reading the whole piece instead of just a headline?
Sacrilege! People don't have to read the article to have an opinion. This is the internet.
Sacrilege! People don't have to read the article to have an opinion. This is the internet.
For the people saying "fire!"...
Wood went out of fashion because of urban fires, resource (natural forest) depletion and long term maintenance (rot, termites..) issues.
Modern engineered timber (according to proponents) solves these problems. It's engineered from renewable crops of fast growing timber, is resistant to fire and pests... Proponents claim it is now suitable for skyscrapers but certainly for 5-15 story urban residential buildings.
Imo.. what is missing are clear advantages, a reason to bother. I don't think there's much cost advantage at this point. Weight savings.. maybe there are some applications where this is important. Generally, it's a bit of a solution searching for a problem.
Wood went out of fashion because of urban fires, resource (natural forest) depletion and long term maintenance (rot, termites..) issues.
Modern engineered timber (according to proponents) solves these problems. It's engineered from renewable crops of fast growing timber, is resistant to fire and pests... Proponents claim it is now suitable for skyscrapers but certainly for 5-15 story urban residential buildings.
Imo.. what is missing are clear advantages, a reason to bother. I don't think there's much cost advantage at this point. Weight savings.. maybe there are some applications where this is important. Generally, it's a bit of a solution searching for a problem.
Using wood for building is a carbon sequestering process. Compare it to using cement, a process that massively releases carbon.
This is more of a problem with time frames. Wooden houses last 100-200 years if very well built. I've seen teardowns after 50, sometimes less. What's the environmental cost of building 4 wood buildings to last as long as 1 concrete building?
Concrete construction lasts centuries. And if torn down, can be crushed and after separated from rebar, re-used as aggregate in another project.
Concrete construction lasts centuries. And if torn down, can be crushed and after separated from rebar, re-used as aggregate in another project.
The main problem is the environmental damage. The concrete industry is the third largest producer of carbon dioxide emissions in the world. It also represents a third of all landfill waste.
Reinforced concrete is incredibly expensive to repair and maintain. Because of the dozen different ways it can rust and spall, you need to inspect it frequently. The longer you wait to repair it, the more costly it is. A great deal of our reinforced concrete bridges are now structurally unsound. And recycling it is expensive, difficult, and reduces its strength.
Roman concrete lasted centuries, even millennia. But it's very difficult for us to produce concrete of a sufficient quality to last a very long time, as there are many ways to introduce defects. Many of our modern concrete structures wouldn't last a century without significant expensive maintenance.
On the other hand, wood buildings can actually be deconstructed easier, recycled easier, composted easier, don't have a gigantic burden on the environment, and can be made quite strong, as well as lasting for centuries. They're also much easier and cheaper to repair and replace.
I live in the northeast, where 100+ year old wooden homes litter the landscape. The biggest problem with old homes isn't the wood - it's their dated construction methods. My girlfriend lives in what was essentially a wooden barn converted into a house. It wasn't designed or maintained properly, so it's slowly shifting and falling into disrepair. But a well-designed, modern wooden home can last a century or more with maintenance without falling apart.
Reinforced concrete is incredibly expensive to repair and maintain. Because of the dozen different ways it can rust and spall, you need to inspect it frequently. The longer you wait to repair it, the more costly it is. A great deal of our reinforced concrete bridges are now structurally unsound. And recycling it is expensive, difficult, and reduces its strength.
Roman concrete lasted centuries, even millennia. But it's very difficult for us to produce concrete of a sufficient quality to last a very long time, as there are many ways to introduce defects. Many of our modern concrete structures wouldn't last a century without significant expensive maintenance.
On the other hand, wood buildings can actually be deconstructed easier, recycled easier, composted easier, don't have a gigantic burden on the environment, and can be made quite strong, as well as lasting for centuries. They're also much easier and cheaper to repair and replace.
I live in the northeast, where 100+ year old wooden homes litter the landscape. The biggest problem with old homes isn't the wood - it's their dated construction methods. My girlfriend lives in what was essentially a wooden barn converted into a house. It wasn't designed or maintained properly, so it's slowly shifting and falling into disrepair. But a well-designed, modern wooden home can last a century or more with maintenance without falling apart.
Concrete with rebar actually has a shorter lifespan than concrete without rebar, or wood even. Unless the rebar is coated or made from something other than iron/steel, it will eventually rust from absorbed water. Once it does so it expands and cracks the surrounding concrete.
https://theconversation.com/the-problem-with-reinforced-conc...
https://theconversation.com/the-problem-with-reinforced-conc...
More like 500 years. https://en.m.wikipedia.org/wiki/Timber_framing
My gran's cottage was timber framed and I think over 500 years old. She had more problems with the 1970s extension than the old bit http://www.tree-ring.co.uk/images/2010/Dean_Leys.gif
Japan builds houses to last approx 30 years, and it wouldn't suprise me if other first world countries copy that: https://www.theguardian.com/cities/2017/nov/16/japan-reusabl...
I suspect most 80's houses anywhere in the world (concrete or wooden) are rather undesirable.
"What's the environmental cost" is not as relevant to most people as having a modern house, and what's the long term environmental cost of old homes with poor insulation?
I suspect most 80's houses anywhere in the world (concrete or wooden) are rather undesirable.
"What's the environmental cost" is not as relevant to most people as having a modern house, and what's the long term environmental cost of old homes with poor insulation?
My house was built in the 50s. It's perfectly livable, and the wood used for framing is better quality than what is used for construction now.
Compared to cost of new construction, adding proper insulation is nothing, even if you rip out all the drywall.
That said, in my area, old houses aren't torn down because they aren't viable. It's because tearing it down and rebuilding a mcmansion nets you so much more profit/worth.
Compared to cost of new construction, adding proper insulation is nothing, even if you rip out all the drywall.
That said, in my area, old houses aren't torn down because they aren't viable. It's because tearing it down and rebuilding a mcmansion nets you so much more profit/worth.
Yup, we've got a house from 1957, 1800 sq.ft. single storey slab. The whole thing is made of Douglas Fir, super sturdy although a pain in the ass to drive nails into. We're in the process of an interior re-design, and purchase price+slab levelling+reno is going to put us quite a bit lower than new builds around here. Down the street there was a 60s bungalow that was torn down and replaced by two new builds, currently selling for $499k each. That's about $180k more than our total, with less floor area. (Plus, if we ever decide to move... there's the backup plan of "tear it down and build two shitty new builds and sell them for $499k each")
I have a wooden house from the 30’s: because I like the feel and I like the trees.
I should have been clearer: there are houses from the 80's that I love. However there are also many houses from the 80's that are built poorly or are just fugly.
I should have been clearer: there are houses from the 80's that I love. However there are also many houses from the 80's that are built poorly or are just fugly.
I’m in an 80s house right now. It’s pretty desirable. Doubly so because the neighborhood trees have matured nicely. The 60s bungalows nearby are getting torn down though - but mostly due to their small size.
My entire neighborhood is home from the 70s-80s and their value continues to rise every year.
Directly trapping carbon for over 50 years is pretty good, and the main CO2 release in concrete is the cement - both in heating it and the actual reaction necessary to create it. Aggregate availability isn't the issue there.
On top of that, large scale structural concrete is a fairly new technology, and while improvements to longevity have been made, many buildings will be lucky to make it to 100 years.
On top of that, large scale structural concrete is a fairly new technology, and while improvements to longevity have been made, many buildings will be lucky to make it to 100 years.
50 year homes being torn down? Whoa.
I haven't seen anything like that in my experience at all. House I grew up in is still going strong at 65, really quite a baby compared to most around me in my suburb.
Only know of one house which burned down completely, was torn down and rebuilt in the heart of the city.
Most significant damage caused to wood-frame homes tends to allow partial rebuilding and renovation without the need for tearing it all down completely.
I haven't seen anything like that in my experience at all. House I grew up in is still going strong at 65, really quite a baby compared to most around me in my suburb.
Only know of one house which burned down completely, was torn down and rebuilt in the heart of the city.
Most significant damage caused to wood-frame homes tends to allow partial rebuilding and renovation without the need for tearing it all down completely.
There's a lot of ~50 year teardowns where I live, but it's people that want to build something big and ostentatious on the lot in desirable neighborhoods. The homes they are destroying are often all brick construction.
You see it mostly with smaller homes in areas that are desirable. The smaller homes, usually built 50-60 years, tend to have low ceilings, small kitchens, no master bedroom, etc. Some have structural issues due to neglect but most are fine structurally just not desired by buyers.
When the owners decide to sell they usually get snapped up basically for the land cost - demolition cost and are torn down for "teardown" houses. In Chicago it's pretty common. Our street is about a 50% mix of 50s homes and < 10 year old teardown homes.
When the owners decide to sell they usually get snapped up basically for the land cost - demolition cost and are torn down for "teardown" houses. In Chicago it's pretty common. Our street is about a 50% mix of 50s homes and < 10 year old teardown homes.
If you want to see what full neighborhood teardowns look like, plan a visit to Vancouver, BC. The number of McMansions popping up all over the place is shocking.
Does concrete last centuries when reinforced with steel?
I know next to nothing about building construction, but I saw this article recently, which suggests it doesn't:
https://theconversation.com/the-problem-with-reinforced-conc...
found via http://www.notechmagazine.com/2018/09/no-tech-reader-21.html
I know next to nothing about building construction, but I saw this article recently, which suggests it doesn't:
https://theconversation.com/the-problem-with-reinforced-conc...
found via http://www.notechmagazine.com/2018/09/no-tech-reader-21.html
Most buildings for which you'd consider wood will probably be torn down before they become structurally unsound simply because a different building will be desired (bigger / different purpose).
Also, is concrete actually reused like this at scale? Sounds unfeasible economically.
Also, is concrete actually reused like this at scale? Sounds unfeasible economically.
This is great; another way for warming enthusiasts to put their money where their mouths are. We should see new wooden cities just as soon as they sell their properties in Manhattan and Miami...
Most people who have the opportunity to build their own homes build them out of wood. It's not like I as a "warming enthusiast" can start rebuilding parts of Manhattan. Even if you are a property owner in New York City, it's unlikely that you will actually rebuild the buildings on your property.
Anyone who believes the predictions has already sold her property in NYC. Perhaps now she is buying up soon-to-be-farmed tundra? In any case we wouldn't expect much new development to occur at elevations near sea level.
I'm not sure why people are unhappy to hear about this new opportunity to simultaneously profit from their knowledge and improve society's organization through their investment signals.
I'm not sure why people are unhappy to hear about this new opportunity to simultaneously profit from their knowledge and improve society's organization through their investment signals.
So if people REALLY believed in global warming they would give up their relatively low impact apartments to take up industrial farming?
I think the main point is that there wouldn't be any new development in ocean-side cities if people believed the sensationalism, not that everyone would take up farming.
Good thing he has you to shrink a bad faith argument to a radically smaller set of claims!
'frockington actually read what I wrote. You imagined something silly like "the world is not warming", which I didn't write. I'm pointing out a real issue here. I'm sure you believe that actions taken by humans will cause earth to warm in disastrous ways. Lots of other people claim to believe that, but as long as their investments say otherwise, we won't really be getting ready for the calamity.
Then there are those who want the government to bail out all the flooded condos in Miami, as if that would reduce this problem...
Then there are those who want the government to bail out all the flooded condos in Miami, as if that would reduce this problem...
[deleted]
Hehe, don’t hold your breath!
Declarations of "whataboutism" incoming, I'm sure. "You can't use my investment decisions to impeach my religious beliefs!"
> Imo.. what is missing are clear advantages, a reason to bother.
There are quite a few actual advantages. Speed of construction is one. The ability to prefabricate large elements (like entire walls) off site is another. In some areas of the world there's a lot of cheap excess timber after some kind of pest (I'm thinking a beetle?) killed entire forests. It insulates really well out of the box, especially when it comes to noise insulation. Wooden buildings are more earthquake resistant than stone/concrete.
There's also quite a number of disadvantages with concrete. Lack of sand. Implication climate change. Requires rebar reinforcements which ups the price and turns the whole thing into a giant radiator.
CLT is a pretty awesome building material, really.
There are quite a few actual advantages. Speed of construction is one. The ability to prefabricate large elements (like entire walls) off site is another. In some areas of the world there's a lot of cheap excess timber after some kind of pest (I'm thinking a beetle?) killed entire forests. It insulates really well out of the box, especially when it comes to noise insulation. Wooden buildings are more earthquake resistant than stone/concrete.
There's also quite a number of disadvantages with concrete. Lack of sand. Implication climate change. Requires rebar reinforcements which ups the price and turns the whole thing into a giant radiator.
CLT is a pretty awesome building material, really.
> In some areas of the world there's a lot of cheap excess timber after some kind of pest (I'm thinking a beetle?) killed entire forests.
Dead wood isn't even useful as firewood. You can't just pick dead trees up off the forest floor and saw them up into lumber. Even if you could, no government would let you transport that timber out of the immediate vicinity in which it was found, due to the aforementioned pest.
Perhaps there is a surplus of cheap excess timber in some areas of the world, but there isn't much chance of that having anything to do with any kind of pest.
Dead wood isn't even useful as firewood. You can't just pick dead trees up off the forest floor and saw them up into lumber. Even if you could, no government would let you transport that timber out of the immediate vicinity in which it was found, due to the aforementioned pest.
Perhaps there is a surplus of cheap excess timber in some areas of the world, but there isn't much chance of that having anything to do with any kind of pest.
"Dead wood isn't even useful as firewood"
Sure it is. You mean degraded, rotten dead wood .. but "fresh" dead wood is firewood.
Sure it is. You mean degraded, rotten dead wood .. but "fresh" dead wood is firewood.
That's a fair distinction to make.
When a tree is killed by a pest such as the emerald ash borer, it dies because the boreholes allow fungus and bacteria into the core of the tree. By the time the tree is visibly dead, very little of the wood is 'fresh'. It cannot be used as lumber, or even firewood.
When a tree is killed by a pest such as the emerald ash borer, it dies because the boreholes allow fungus and bacteria into the core of the tree. By the time the tree is visibly dead, very little of the wood is 'fresh'. It cannot be used as lumber, or even firewood.
CLT is being made from mountain pine-beetle infested wood in the US. So not quite as useless as you seem to be implying ...
It looks like you're correct about the mountain pine beetle infestations, which I wasn't familiar with. Not that you can pick trees up off the forest floor, but in some drier areas the pines apparently remain standing and commercially usable for a few years.
Snags (dead and fallen trees held up by their neighbors) make excellent firewood and in some cases useful lumber, as it has already been cured!
I think this could also relate to the wood from the trees surrounding an infected tree. These can often also be cut down as a kind of quarantine, and are likely to have good quality wood.
> There's also quite a number of disadvantages with concrete. Lack of sand.
This is good point. One would think that sand is unlimited supply, but that's actually not the case:
https://www.businessinsider.com/world-running-out-sand-resou...
This is good point. One would think that sand is unlimited supply, but that's actually not the case:
https://www.businessinsider.com/world-running-out-sand-resou...
I find it interesting that the article you linked to doesn't mention one usage of sand that I'd expect it to - namely proppant for fracking.[1]
It seems like just yesterday the harmful effects of fracking were the topic of countless articles, and now even an article where it would naturally fit in overlooks them. I wonder why?
[1]https://info.drillinginfo.com/proppant-the-greatest-oilfield...
It seems like just yesterday the harmful effects of fracking were the topic of countless articles, and now even an article where it would naturally fit in overlooks them. I wonder why?
[1]https://info.drillinginfo.com/proppant-the-greatest-oilfield...
To elaborate, from the link:
"The first experiments in the 1940s used around 150 pounds of sand, but now it’s around 5 million pounds per well."
"the proppant industry is definitely up and to the right – 57 billion lbs in 2012"
"The first experiments in the 1940s used around 150 pounds of sand, but now it’s around 5 million pounds per well."
"the proppant industry is definitely up and to the right – 57 billion lbs in 2012"
> The ability to prefabricate large elements (like entire walls) off site is another.
You can do that with concrete as well [1], it's often called precast concrete. concrete wall sections are heavier than wood wall sections, so you do need larger equipment, and tend to have smaller pieces.
[1] https://en.wikipedia.org/wiki/Precast_concrete
You can do that with concrete as well [1], it's often called precast concrete. concrete wall sections are heavier than wood wall sections, so you do need larger equipment, and tend to have smaller pieces.
[1] https://en.wikipedia.org/wiki/Precast_concrete
That's a good point. I guess trucking lighter wood around makes more sense than heavier concrete, but still. I've also noticed prefab sections of brick facades being trucked around.
> There is also, alongside the environmental and economic, an aesthetic-psychological case for wood cities. Clare Farrow, who is co-curating a current London exhibit called “Timber Rising–Vertical Visions for the Cities of Tomorrow,” wrote in Dezeen, Studies are showing that the presence, scent and touch of wood can have remarkably positive effects, not only on people’s wellbeing in a general sense, but more specifically on stress levels, blood pressure, communication, learning and healing.” A 2015 review in Wood Science and Technology supports her claims and also suggests that “specific aspects of wood such as colour, quantity, and grain pattern should be examined"
Of course, I don't need a study to tell me that wood is nice.
Of course, I don't need a study to tell me that wood is nice.
You can easily achieve the same effect by adding wood panels to visible parts of the interior. No need to build the entire thing with wood.
Retro!
I'm surprised that plastering every wall with wood paneling isn't a bigger thing with hipsters. (or is it and I haven't noticed?)
I'm surprised that plastering every wall with wood paneling isn't a bigger thing with hipsters. (or is it and I haven't noticed?)
You probably shouldn't be smelling or touching the wood frame of your home. If you do, there is a bad problem with your drywall.
Here, just take a look at this Google image search for cross-laminated timber architecture, it'll help you guys to make comments that aren't so ill informed and off-base:
https://www.google.ca/search?biw=1919&bih=947&tbm=isch&sa=1&...
https://www.google.ca/search?biw=1919&bih=947&tbm=isch&sa=1&...
This reminds me of how beautiful properly-crafted wood can be, as well as functional. I'm reminded of Frank Lloyd Wright's & the Prairie School's emphasis on working "honestly" with materials.
[deleted]
You're generalizing. In my part of the States, EVERY home has a basement. That basement is usually unfinished. They'll leave exposed framing on half-walls and walk-outs. It's up to the buyer to determine whether more livable space is necessary (and therefor drywall).
Modern wood for building storied buildings is not like 'wood' people think about when they hear the word. It's a laminated material, the strenght of which very much depend on cutting edge expoxy technology. I don't know how environmentally friendly it is, but this is not a log cabin we're talking about.
Yep, and it's not like "modern" glues/resins have been proved to last for centuries and/or be totally harmless for the humans living in the houses.
Think of formaldehyde based glues (widely used):
https://en.wikipedia.org/wiki/Urea-formaldehyde
https://en.wikipedia.org/wiki/Urea-formaldehyde#Health_conce...
Think of formaldehyde based glues (widely used):
https://en.wikipedia.org/wiki/Urea-formaldehyde
https://en.wikipedia.org/wiki/Urea-formaldehyde#Health_conce...
> Imo.. what is missing are clear advantages, a reason to bother.
Sand depletion [0], recyclability
[0] https://www.smithsonianmag.com/science-nature/world-facing-g...
Sand depletion [0], recyclability
[0] https://www.smithsonianmag.com/science-nature/world-facing-g...
> Generally, it's a bit of a solution searching for a problem.
err, the little something called the environment?
err, the little something called the environment?
When wood burns (at least CLT Beams) it has a much longer time until failure than steel. When steel gets hot, it quickly loses its structural strength, and can collapse.
A lot of people are saying sand shortage, but surely weight savings matter more? If your building is 6x lighter your foundations can presumably be a lot cheaper?
In that case, you should be comparing engineered wood with concrete that includes basalt fiber composite rebar [0] and weight-cutting aggregates like expanded polystyrene beads [1] and loose (basalt|carbon|glass) fiber. In small-building construction, a no-steel concrete wall could be just 2 inches thick where steel-concrete building code might mandate minimum 8 inches just to prevent swelling rebar from destroying the wall from the inside. Also, basalt rebar is trivially bendable, so curved shells can add strength from geometry where straight steel rebar would be limited to using rollers to bend every bar to the correct curvature or to use doubly ruled surfaces like one-sheet hyperboloids and hyperbolic parabolas. And more non-sand aggregate means sand shortage has less impact, right?
There are a lot of ways to save weight on buildings, but not all of them translate well to building codes that can be used by building contractors without having a staff engineer on site to determine whether the equations work out to acceptable structural strength or not. And all the building codes out there for wood are going to be for standard dimension lumber, and not specific types of engineered wood. Until the codes are updated, the building inspector will look at your cross-laminated composite wood beams, look them up in his book, and tell you that your plans don't conform to code.
Not to mention that once your houses are light enough to blow away in a strong wind, now you need to anchor them to the ground with cables and hooks, and wind forces and the stresses at the anchor points become a whole new engineering problem.
Cities aren't going to be made of "wood". They'll have to be made of ANSI/ISO-standard-X-conformant structural members and ANSI/ISO-standard-Y-conformant processes. We'll get there. Slowly.
[0] https://en.wikipedia.org/wiki/Basalt_fiber
[1] https://en.wikipedia.org/wiki/Expanded_polystyrene_concrete
There are a lot of ways to save weight on buildings, but not all of them translate well to building codes that can be used by building contractors without having a staff engineer on site to determine whether the equations work out to acceptable structural strength or not. And all the building codes out there for wood are going to be for standard dimension lumber, and not specific types of engineered wood. Until the codes are updated, the building inspector will look at your cross-laminated composite wood beams, look them up in his book, and tell you that your plans don't conform to code.
Not to mention that once your houses are light enough to blow away in a strong wind, now you need to anchor them to the ground with cables and hooks, and wind forces and the stresses at the anchor points become a whole new engineering problem.
Cities aren't going to be made of "wood". They'll have to be made of ANSI/ISO-standard-X-conformant structural members and ANSI/ISO-standard-Y-conformant processes. We'll get there. Slowly.
[0] https://en.wikipedia.org/wiki/Basalt_fiber
[1] https://en.wikipedia.org/wiki/Expanded_polystyrene_concrete
What about surviving fires without structural weakening? An average apartment building has to endure many fires over its lifetime.
(Maybe it's a nonproblem and you can replace the damaged wood easily, or the fires don't typically do permanent damage, i don't know.)
(Maybe it's a nonproblem and you can replace the damaged wood easily, or the fires don't typically do permanent damage, i don't know.)
Actually timber has a nice property of loosing strength gradually and slowly in case of fire, giving time for people to escape. Steel and concrete reinforced structures tend to collapse when a certain temperature is reached.
Yes, but my point was that after a "routine" fire the building might be declared weakened and require big overhauls or teardown, whereas a traditional apt building can stroll through many small/moderate fires. Because eg a 50 apartemnt building over 100 years is likely to experience many fires. This may impact investoe expected roi and/or insurance costs.
Steel and concrete buildings need a huge amount of time to get fires spread enough and hot enough to collapse, except in freak catastrophes like jet plane crashes.
It's a well known and not uncommon failure mode:
https://youtu.be/8XMTALBYRNA?t=40
https://youtu.be/LB9wwTmrMYA?t=15
Fireproofing steel beams has been practiced since the 1950s. (https://www.asbestos.com/products/fireproofing-fire-preventi...)
https://youtu.be/8XMTALBYRNA?t=40
https://youtu.be/LB9wwTmrMYA?t=15
Fireproofing steel beams has been practiced since the 1950s. (https://www.asbestos.com/products/fireproofing-fire-preventi...)
as a layman, i assume that our wood techniques are not yet at the level where you can use it for twin tower scale buildings, but this raises an interesting question for me anyway. if such a building had all its structural elements made of wood, would it be likely to suffer the same catastrophic weakening in the event of a 767 strike?
ever played jenga?
How about natural disasters such as hurricanes in the east, earthquakes in the west and flooding elsewhere?
I'm not a structural engineer so I would like to know if there are some possibilities here that I may not be seeing.
I'm not a structural engineer so I would like to know if there are some possibilities here that I may not be seeing.
Pick a building material, you can construct it with modern methods to resist natural disaster. Even wooden homes can resist hurricanes and earthquakes now. The biggest concern for wood is still fire, but we have much better ways to manage it and make the wood fire-resistant.
I recall talk recently about a shortage of sand appropriate for creating cement. It seems that this compressed wood turns that potential shortage into an opportunity.
Talk of sand shortages anywhere but in extremely remote and non-sandy locations is ridiculous. Sand is among the cheapest materials on earth. If it ever became difficult to procure, the price would rise.
Except that the price has risen. Easily procurable sand (typically from river beds) is being depleted, and no the desert sand isn't any good for construction.
https://www.wsj.com/articles/latest-threat-to-u-s-oil-drille...
https://fred.stlouisfed.org/series/WPS1321
https://www.wsj.com/articles/latest-threat-to-u-s-oil-drille...
https://fred.stlouisfed.org/series/WPS1321
The price has risen slowly and steadily for decades? And it's still the cheapest commodity around? I don't see the problem...
Plenty of sand in the Sahara, last I checked.
Concrete doesn't need "sand", it needs "sharp sand". You get sharp sand from river beds. You don't get it from deserts. The wind erosion causes round grains, and those are not useful for concrete.
Nice little summary here https://www.youtube.com/watch?v=V2349cn0-T0
Who knows, maybe the sand shortage will get severe, driving concrete prices up to the point where people start looking for alternatives.
> A recent advance in wood technology should interest the neighborhood’s developers: Teng Li, a University of Maryland mechanical engineer, created with his colleagues wood that’s as “strong as steel, but six times lighter,” he said. Liangbing Hu, Li’s co-author on the study, added, “This kind of wood could be used in cars, airplanes, buildings—any application where steel is used.” Making it is just a two-step process. The scientists first boiled natural wood in a mixture of sodium hydroxide and sodium sulfite, to remove some of the lignin and hemicellulose, substances contained in the walls of wood cells (the former retard parasite and bacterial attacks, the latter cover and bind fibers). Then they put the wood in a hot press, which leads, as they say in the paper, “to the total collapse of cell walls and the complete densification of the natural wood with highly aligned cellulose nanofibres.” The result, they conclude, is a “low-cost, high-performance, lightweight alternative” to “most structural metals and alloys.”
If this decreases the burn rate, as other commenters have pointed out, and the input energy is manageable, then this has a chance. Cool!
If this decreases the burn rate, as other commenters have pointed out, and the input energy is manageable, then this has a chance. Cool!
The obvious question, to me, is whether this process can be used to produce a uniform enough product to be highly reliable.
If you can extrude or shape the densified wood, into something "branch-like" but at steel like strength then you open up new building opportunities - our cities are dominated by straight lines, for good reasons, but branchlike handrails, footpaths and arches open up a lot of possibilities for good architects to chnage the look of a city beyond the mere material it is made of
There is a compression step in wood preparation life cycle. You could replace this step with shaped moulds to create these features. Or maybe it's cheaper and easier to 3D route out of bigger masses.
just wondering how much pressure it takes to compress wood to destroy the cellular structure. One might suspect more than enough to crack a mould that had lovely curvy shapes in it ...
> Teng Li, a University of Maryland mechanical engineer, created with his colleagues wood that’s as “strong as steel, but six times lighter,” he said
Phrases like this make me uneasy. "Strength", especially when used informally like this, is quite ambiguous (e.g. there's a reason we don't make buildings out of spider silk).
Overall it's quite an uplifting piece though, and I would certainly like to see such a revival.
Phrases like this make me uneasy. "Strength", especially when used informally like this, is quite ambiguous (e.g. there's a reason we don't make buildings out of spider silk).
Overall it's quite an uplifting piece though, and I would certainly like to see such a revival.
First of all, what they are talking about is more like paper made out of wood since the fibers are treated extensively and then formed. Secondly, large and spreading structure fires which have such a devastating history have been essentially eliminated by use of sprinkler systems.
Even if the technology is perfected and proven superior on several counts, the adoption has to overcome the psychological barrier. The places that don't have a culture of wooden buildings, especially the floor, will need some convincing.
As an Indian, I don't encounter wooden floor often. Modern buildings are all brick and reinforced concrete, and old temples are stone mostly. Any wooden floor one might come across are just wood panels installed on concrete floor. Nearly two decades back, the city library (Seshadri library, Bengaluru) was renovated, and as a part of it the shelves were raised and a wooden corridor was installed to enable access to higher shelves; its a tall building with a dome and a large hall under it, your typical library. Needless to say, I was quite apprehensive to walk on it, so were most people there. Apart from that, the only experience I have is standing on my desk to change the bulb. The desk is quite sturdy - the bulkier carpenter stood on it to demonstrate - but I just can't trust it the same way I trust concrete floor. When on a wooden surface, I step softly, hoping to make myself lighter, just in case, though I know its nonsense.
As an Indian, I don't encounter wooden floor often. Modern buildings are all brick and reinforced concrete, and old temples are stone mostly. Any wooden floor one might come across are just wood panels installed on concrete floor. Nearly two decades back, the city library (Seshadri library, Bengaluru) was renovated, and as a part of it the shelves were raised and a wooden corridor was installed to enable access to higher shelves; its a tall building with a dome and a large hall under it, your typical library. Needless to say, I was quite apprehensive to walk on it, so were most people there. Apart from that, the only experience I have is standing on my desk to change the bulb. The desk is quite sturdy - the bulkier carpenter stood on it to demonstrate - but I just can't trust it the same way I trust concrete floor. When on a wooden surface, I step softly, hoping to make myself lighter, just in case, though I know its nonsense.
With the mention of temples, it's actually pretty common for historical temples, churches, and castles to have wooden rooms for anything past the ground floor, since it was much, much easier to build a few main structural supports out of stone and then fill in the rest with wood later.
Of course, I'm a little biased on the subject, living in a 100-year-old all-wooden building (you can see the huge beams resting on the foundation in the basement) that I chose for earthquake resistance. I'm actually a lot more comfortable knowing that the whole building can sway while all the parts stay attached, compared to the many old brick buildings around here that will literally fall apart if an earthquake happens.
Of course, I'm a little biased on the subject, living in a 100-year-old all-wooden building (you can see the huge beams resting on the foundation in the basement) that I chose for earthquake resistance. I'm actually a lot more comfortable knowing that the whole building can sway while all the parts stay attached, compared to the many old brick buildings around here that will literally fall apart if an earthquake happens.
For those interested in more "concrete" expressions of the existing capabilities of timber based construction an 18 story dormitory was assembled in 70 days at the University of British Columbia.
https://news.ubc.ca/2016/09/15/structure-of-ubcs-tall-wood-b...
Here's a time-lapse: https://www.youtube.com/watch?v=GHtdnY_gnmE