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As Mass Timber Takes Off, How Green Is This New Building Material?

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Re: As Mass Timber Takes Off, How Green Is This New Building Material?

#61

Post by kaybe »

perfunctory wrote: post #32
rjf72 wrote: post #16

Would this not be just another form of kicking the can? In particular once these buildings are demolished and replaced with new ones, I don't imagine that the old wood would (or even could) be reused. Instead it'd be sent to a landfill and decay at which point its stored carbon would be released. In favor of this regardless. Wood is so much more pleasant on the eyes, and creating an incentive for huge sustainable for…

> Instead it'd be sent to a landfill and decay at which point its stored carbon would be released. Even then it's still carbon neutral. Or am I missing something? Or, since carbon is gonna be released anyway, we could burn it and make some energy as a bonus.

Apart from the energy used in harvesting, transport and construction (if not carbon-neutral), yes.

However, what you actually do is add a new carbon sink, with a flux in and a flux out, just like the eco-system, the ocean, the atmosphere etc. As long as you keep the outflow lower or equal than the inflow it's a net win.

Edit: Another point - we might not be in a position to think about this at the moment, but we should not store all available carbon in rock form (some of the carbon sequestration ideas lead to rockform carbon basically) because our descendents may really need it one day.

Re: As Mass Timber Takes Off, How Green Is This New Building Material?

#62

Post by RickJWagner »

proee wrote: post #24

Termites are going to love this ;-) Even with termite treated lumber, they will still need annual inspections to look for damage. If they do find out the structure is laden with termites, it would most likely require a complete evacuation of the building and "tenting" to gas them out - which might be tricky if it's in an urban area. Also, any undetected leaks in the structure could cause slow rotting of the wood.

Termites are kind of regional. Other regions have powder-post beatles and other destructive insects.

But your point is valid. Wood is susceptible to rot, bugs, fire, etc.

Re: As Mass Timber Takes Off, How Green Is This New Building Material?

#63

Post by marmaduke »

willyt wrote: post #35
barrkel wrote: post #20

Earlier quoted context omitted.

Sure, but we have concrete buildings still standing from Roman times - most famously, the Pantheon. I grew up in a cottage a couple of hundred years old, with thick walls built from stone and mortar. It's not unusual to live in a house that's over a century old in Europe. I've also lived in a wooden house - more of a three room + toilet chalet, really. Biggest irritations were all the noises from thermal expansion in…

Roman concrete doesn’t have the same chemistry as modern concrete.

What’s different? I’m aware of the modern mix with cement sand stone, but I’m guessing romans didn’t have the cement?

Re: As Mass Timber Takes Off, How Green Is This New Building Material?

#64

Post by lorenb »

srfilipek wrote: post #58
Tharkun wrote: post #12

Earlier quoted context omitted.

This question comes up every single time anything related to wood construction is talked about. The keyword in mass timber is mass . It's quite hard to set a big mass of wood on fire. It burns slowly and relatively predictably -- meaning you have more time to evacuate. And because of its mass, an outer layer can char, burn out and leave the building standing. Also sprinklers.

The problem is the glue. When the glue melts (which it does at a much lower temperature than wood burns), the structural integrity is lost. Firefighters do not enter new construction homes in the US because they often use these as floor joists. The time until failure has been greatly reduced compared to older homes. Things may have gotten better in the last few decades, but I'd like to see the data.

You’re thinking of I-joists, which are a kind of engineered lumber, not a kind of mass timber. And those do light up like kindling. The glue used in glulams and the like chars at the same rate as the wood, and it’s pretty easy to achieve known fire ratings simply by making the members a little chunkier than they need to be since the char rate is known.

Re: As Mass Timber Takes Off, How Green Is This New Building Material?

#65

Post by imtringued »

eeZah7Ux wrote: post #52
WalterBright wrote: post #34

Earlier quoted context omitted.

There's a great deal of land that could be covered with planted trees, which pull CO2 out of the air. When they are mature, then they can be used as building material, and a new tree planted.

> planted trees, which pull CO2 out of the air When an old building is torn down and the wood is burnt all the CO2 goes back into the environment. Unless we start burying old wood into sealed underground chambers (like depleted oil wells) all the CO2 stays around.

Concrete isn't carbon neutral therefore mass timber can still be better for the environment.

Re: As Mass Timber Takes Off, How Green Is This New Building Material?

#66

Post by dsfyu404ed »

jabl wrote: post #40
willyt wrote: post #35

Earlier quoted context omitted.

Roman concrete doesn’t have the same chemistry as modern concrete.

And, Roman concrete doesn't have steel rebar which rusts and cracks the concrete.

Eh, properly done reinforced concrete should last hundreds of years.

Of course it's possible to use the wrong concrete formula for the job (the concrete for your driveway is not the same as the concrete for a boat ramp) but if done right it should last.

Re: As Mass Timber Takes Off, How Green Is This New Building Material?

#67

Post by Tharkun »

srfilipek wrote: post #58
Tharkun wrote: post #12

Earlier quoted context omitted.

This question comes up every single time anything related to wood construction is talked about. The keyword in mass timber is mass . It's quite hard to set a big mass of wood on fire. It burns slowly and relatively predictably -- meaning you have more time to evacuate. And because of its mass, an outer layer can char, burn out and leave the building standing. Also sprinklers.

The problem is the glue. When the glue melts (which it does at a much lower temperature than wood burns), the structural integrity is lost. Firefighters do not enter new construction homes in the US because they often use these as floor joists. The time until failure has been greatly reduced compared to older homes. Things may have gotten better in the last few decades, but I'd like to see the data.

There are various ways of joining large amounts of wood together. CLT uses glue. Brettstapel uses wooden dowels (using two kinds of wood with a different hardness, so the dowels stay in place). I'm sure there are other variants as well.

Re: As Mass Timber Takes Off, How Green Is This New Building Material?

#68

Post by Harvey-Specter »

radicalbyte wrote: post #22
mjevans wrote: post #3

I would like to know more about the long term stability of the glues involved and how the entire structure as a whole decays / fails over what timeframes under what exposures. Most other building materials in use today, the actual core structural elements, have withstood the test of centuries of use and are well proven and stable technologies.

Timber at least can last a very long time. There are houses in the UK which dates from the time of Shakespeare which are still standing. I'm not sure what's worse: a cheap wooden structure which lasts 50-100 years or a strong brick structure which lasts hundreds. Here in Europe we have a large stock of houses from the 1950's which cost 300 EUR a month to heat and cannot be insulated. For a modern passive house costs…

Any building can be insulated, you just have to spend the money and sacrifice some internal space. Frame the inside of the walls and put in insulation.

Re: As Mass Timber Takes Off, How Green Is This New Building Material?

#69

Post by myspy »

masonic wrote: post #46
myspy wrote: post #42

Earlier quoted context omitted.

I have read that termites live in the earth, which means a sufficient foundation should avoid that they can reach the wood?

Drywood termites fly.

Damn, nature has always a solution.

Re: As Mass Timber Takes Off, How Green Is This New Building Material?

#70

Post by alkonaut »

benj111 wrote: post #6
paulsutter wrote: post #2

The correct term is CLT (cross laminated timber). A big chunk of Katerra’s recent big financing is to pay for CLT factories. The cool thing about CLT is that it can be “printed” in arbitrary shapes and sizes in a factory setting and shipped to construction sites for rapid assembly. Structurally it can replace steel/concrete in a certain range of structures. The potential for automation and mass customization is absen…

Came here to say this, I've heard it called 'glue lam' also. Who the hell thought up the mass timber name though?! That just says to me a solid (mass) of unengineered wood.

Gluelam is usually used for the older (more established) technicque of just making structural wood beams that are larger than can normally be sawn in one piece. E.g. the largest dimension of regular lumber may be 50x200mm, but you can make a 100x500 gluelam cross section by simply gluing five 100x50 on top of each other. That also has the benefit of being stronger than the individual parts because their weaknesses are averaged (much like how a spun rope works).

So Gluelam beams are used as an alternative to steel beams.

This more recent tech is cross-laminated-timber (CLT) where flat pieces of timber and sheathing is glued together to form large construction elements (walls, floor sections) CLT is used as an alternative to building modules. E.g. CLT can form a floor slab between storeys of a highrise, or a wall section where you would otherwise use a prefab concrete or steel/glass piece.

It is true that CLT is both "glued" and "laminated" (so it is a kind of glue-lam) but using just "gluelam" was established already as short for "gluelam beam".

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