Timber Towers Are On the Rise in France (citylab.com)

A reader shares a report: Spurred by concerns over climate change and the negative impacts of concrete manufacturing, architects and developers in France are increasingly turning to wood for their office towers and apartment complexes. Concrete was praised through much of the 20th century for its flexibility, functionality, and relative affordability. In France, the material ushered in an era of bold modernist architecture including housing by Auguste Perret and Le Corbusier. Today, however, wood is lauded for its smaller environmental footprint and the speed with which buildings can be assembled. "Wood had largely disappeared and was seen as a quaint material," says Steven Ware, a partner at the architecture firm Art & Build, whose latest wooden office building opened in Paris's 13th arrondissement earlier this summer. "[But] the energy it takes to put a concrete building up, to run it, and then dismantle it when it becomes obsolete was too much. Using mass timber in office buildings seemed like something we had to do." The production of cement, one of the main ingredients in concrete, generates an estimated 5 percent of the world's carbon emissions. Trees, in contrast, capture CO2, helping offset emissions produced by a typical building process. And then there's the string of other construction advantages that make wood economically appealing. It's lighter, which means digging smaller foundations in the ground. Crane costs come down, as they're no longer hauling blocks of cement hundreds of feet in the air. Driving a nail into a slab of wood requires a lot less energy than driving one into concrete. Months can be knocked off the construction timeline.

Comments

Addressing Some of the Objections Here

[careysub]

Wood can be grown and harvested sustainably on tree farms where generation after generation of trees selected for structural properties and rapid growth are cultivated. Any such "green" inspired building program should/would ensure that all the timber used comes from such sources. And so yes, building permanent structures out of wood does lock up CO2 as long as the structures stand - whereas CO2 released in the production of concrete is in the air for centuries.

The actual material used for framing a structure has nothing to do with the fire safety (or lack of same) in an inhabited structure. Metal and concrete framed structures are no safer on that count than wood. The fire hazard that threatens life is entirely due to the furnishings and utilities inside the structure. By the time a frame of wood frame building starts to burn the interior is already destroyed, and the inhabitants have either escaped or are dead. Note that modern construction techniques using fire proof gypsum board that isolates the structure from the interior (gypsum does not burn and actually absorbs energy as it decomposes).

Wood is a pretty remarkable material. It is in fact an advanced composite material produced by natural nano-factories. It compares favorably with far more expensive synthetic composites, and beats them all in cost. Used properly (taking advantage of the anisotropic properties of wood beams) a good wood beam comes with a factor of 3 in stiffness/weight ratio of the best performance ofunidirectional carbon fiber epoxy composite, and beats structural steel. Sitka spruce is used in the upper stage of Trident II SLBM missile since it had the best properties for the role, over all other candidates.

Re:Addressing Some of the Objections Here

[G00F]

That was quite some detail in that report. I read parts and skimmed the rest. It basicaly concludes; Tests/sudies done showing large timber structures to have comparible safety, but have concerns with earth quake/fire combo, but with a 2hr fire resist seam fine with. Also a lack of large of full scale tests.

All in all, it looks positive for large timber use, they just want more data and better refinement of requirements for the building code and such.

Re: Trading one problem for another

[Oswald McWeany]

Also there is a fair amount of carbon sequestered in the building itself. That's assuming the building doesn't burn, which is why I won't get into a tall wooden structure.

The type of wood buildings they're making nowadays don't burn very easy. (not talking about timber framed houses like the US, but the kind used for taller buildings such as this article). They take wood- cut it in strips, arrange the strips in alternating directions (for added strength) and then glue them together with a fireproof glue.

They're actually more fire-safe than steel buildings. Steel will melt or lose strength with fire (as in 9/11 twin towers)- the modern timber buildings resist fire at higher temperatures than it takes for steel to lose integrity.