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Schroder Member
Joined: 26 Oct 2007 Posts: 6722 | TRs | Pics Location: on the beach |
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Schroder
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Mon Sep 23, 2019 8:48 am
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So says the Nature Conservancy and others:
Tall buildings out of timber? In the face of climate change, Seattle encourages it
Quote: | In the coming years, Ballard will be home to Seattle’s first tall building built almost entirely from wood. Rising eight stories from the current Ballard Blossom florist on Market Street will be a hotel built principally from cross-laminated timber, or CLT — durable panels made from binding layers of wooden planks with adhesive. |
Quote: | The huge environmental benefits of cross-laminated timber are its biggest draw: Construction on a cross-laminated timber high-rise emits roughly 25% less carbon dioxide than if the high-rise were concrete, according to a University of Washington study. |
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thunderhead Member
Joined: 14 Oct 2015 Posts: 1519 | TRs | Pics
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Timber buildings are also flammable. Give me a steel core, and only a steel core.
If you want to use that stuff for nonstructural, go for it.
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IanB Vegetable Belayer
Joined: 21 Jul 2010 Posts: 1062 | TRs | Pics Location: gone whuljin' |
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IanB
Vegetable Belayer
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Mon Sep 23, 2019 12:18 pm
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"Forget gaining a little knowledge about a lot and strive to learn a lot about a little." - Harvey Manning
"Forget gaining a little knowledge about a lot and strive to learn a lot about a little." - Harvey Manning
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mb Member
Joined: 11 Aug 2002 Posts: 507 | TRs | Pics
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mb
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Mon Sep 23, 2019 12:23 pm
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thunderhead Member
Joined: 14 Oct 2015 Posts: 1519 | TRs | Pics
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Sure you can make a wood beam fat enough so that it has some extra mass to delay its failure in a fire but what about the joints? A little burning there will open things up in a way they never would in a proper steel component.
Not to mention, steel doesnt add to fuel loading.
Seems to me if you want to sequester carbon, doing so in the structural components of inhabited high rises is a pretty poor place to put it. Dumping that load of logs in a high cold desert and building your structure out of steel, the way it should be, seems much cheaper in both lives and money.
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Bernardo Member
Joined: 08 Feb 2010 Posts: 2174 | TRs | Pics Location: out and about in the world |
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Bernardo
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Mon Sep 23, 2019 4:03 pm
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25% advantage seems probably close enough to be within the margin of error.
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Stefan Member
Joined: 17 Dec 2001 Posts: 5093 | TRs | Pics
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Stefan
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Mon Sep 23, 2019 4:50 pm
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the building probably is built out of wood because it will cost less. probably has nothing to do with desire for carbon footprint.
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Randito Snarky Member
Joined: 27 Jul 2008 Posts: 9513 | TRs | Pics Location: Bellevue at the moment. |
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Randito
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Mon Sep 23, 2019 5:14 pm
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Timber/gluelam construction is less CO2 emitting simply because manufacturing steel and concrete emit a lot of CO2.
I wonder to what extent this affects the life cycle CO2 emissions of a building. After including all the CO2 emissions from heating, lighting and cooling the building of say a century of occupancy.
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grannyhiker Member
Joined: 29 Jul 2006 Posts: 3519 | TRs | Pics Location: Gateway to the Columbia Gorge |
By cutting down trees (more needed for more wood buildings) we reduce the ability of the forest to sequester carbon for the next 50 or so years it takes for the forest to grow back. Be sure to throw that into the calculations!
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view.--E.Abbey
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view.--E.Abbey
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Pyrites Member
Joined: 16 Sep 2014 Posts: 1884 | TRs | Pics Location: South Sound |
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Pyrites
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Tue Sep 24, 2019 1:31 am
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Don’t worry about steel burning or melting. Depending on the steel about half it’s strength is gone at 1000-1100f. Depending on use (beam, bolt, long tie rod) change in dimension might matter too. If you see some above the ceiling and it looks as steel has white stuff sprayed on, it does. Insulation to protect in fire.
Mass timber, often narrowed down to CLT, or cross-laminated timber. Currently it’s not likely cheaper that steel and concrete for a given building. It is much faster. The parallel to a steel fab shop for mass timber is CNC. Wood will change dimension slightly with humidity. The CNC cutting of the wood is to nearly aircraft industry tolerances. Instead of a door opening being a little out of square, and maybe planned to be 5/8” oversized, opening cut by CNC is for practical purposes is perfectly square, with perfect tolerances. Same with all the cuts for the whole building.
Fasteners, back to steel. So you bury some in the wood, others you use some of that fancy intumescent stuff from Hilti or similar. One way or another they are insulated too.
Wall floor or other joints. Adhesives meeting a spec is required, so it it shouldn’t leak air, or smoke.
Currently you can build apartments, hotels, to 18 stories in WA or OR.
Really tall buildings people are putting out on their webpage. I guess it’s just to advertise their firm - fantasy only.
There is some concern among fire community about supertall. All current fire testing has been in a null wind condition. Aloft winds are more common and stronger. Ask your local structural or wind farm P.E.
Not just theoretical. Fire fighters have been killed in high rise fires when a window on the windward side blows out aloft.
Induced draft. The key to all metallurgy since the copper age. Humans should have the concept that it affects fire intensity down pat.
Assumed by everyone to be the cat’s meow in seismic event.
Best.
Keep Calm and Carry On?
Heck No.
Stay Excited and Get Outside!
Keep Calm and Carry On?
Heck No.
Stay Excited and Get Outside!
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NacMacFeegle Member
Joined: 16 Jan 2014 Posts: 2653 | TRs | Pics Location: United States |
Grannyhiker wrote: | By cutting down trees (more needed for more wood buildings) we reduce the ability of the forest to sequester carbon for the next 50 or so years it takes for the forest to grow back. Be sure to throw that into the calculations! |
My thoughts exactly! We need to be preserving forests for carbon sequestration. The longer we let forests grow the greater the rate of carbon sequestration they will be able to achieve - that exponential benefit is lost if we keep cutting forests down! Far better to increase use of recycled materials.
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Schroder Member
Joined: 26 Oct 2007 Posts: 6722 | TRs | Pics Location: on the beach |
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Schroder
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Tue Sep 24, 2019 1:05 pm
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drm Member
Joined: 24 Feb 2007 Posts: 1376 | TRs | Pics Location: The Dalles, OR |
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drm
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Tue Sep 24, 2019 2:18 pm
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Grannyhiker wrote: | By cutting down trees (more needed for more wood buildings) we reduce the ability of the forest to sequester carbon for the next 50 or so years it takes for the forest to grow back. Be sure to throw that into the calculations! |
Hmm - if the wood from the trees is in a building, the carbon is still sequestered. Only if it is burned or degraded is the carbon released. Compared to concrete, that is a big carbon benefit. If the trees were still growing, they could sequester more, but I think that is small benefit compared to avoiding concrete mfr.
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Jake Neiffer Member
Joined: 07 Dec 2011 Posts: 825 | TRs | Pics Location: Lexington, OR |
A forests capacity to sequester carbon is optimized if the trees are healthy and at an appropriate stand density. This may require cutting trees to accomplish.
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Bernardo Member
Joined: 08 Feb 2010 Posts: 2174 | TRs | Pics Location: out and about in the world |
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Bernardo
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Tue Sep 24, 2019 5:06 pm
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Nice point GrannyHiker. These calculations are super complex.
Where in the concrete process does the CO2 get expelled? Could it be captured?
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