Because these are literal sky scrapers. Fire on a wood structure is a recipe for catastrophic failure. A fire in a large structure could have similar effects to those large high rise condos that collapsed in Florida from poor maintenance.
This is very likely dangerous deregulation of the fire code to cut costs being “green washed” as a new thing that needs a hell of a lot more scrutiny. Building large structures with wood WAS a thing in the past, it was outlawed because it’s EXTREMELY dangerous when one of those structures ignites.
They’re only getting away with it because these are composite timbers which have been “tested” to be safer. I’m very skeptical that those tests are comprehensive, at least to the point where I would feel comfortable spending a significant portion of my life in one of these buildings.
We’re also living in an era where regulator bodies have been repeatedly weakened by large companies and interest groups.
Does that fire resistance hold up over a decade, two decades, a century, etc? Even if internationally regulatory bodies are 100% in good hands … there’s no way everybody is using the same blend of wood + fire retardant.
Also how realistic are the laboratory conditions? Do the same testing rules apply if an accelerate has been used to increase the burn rate?
What about the human impact? What’s the impact of inhaling smoke off of these? Environmental impact from the gasses inevitably produced?
How repairable is the timber structure in case of fire?
These questions have pretty reasonable answer for steel and concrete because we have decades of experience with it.
I’m not an expert in this space but this seems like an incredibly dangerous gamble to take for not much gain. Concrete and steel are reliable building materials that are mostly issues because of the energy cost to produce them. Fix the energy supply chain and they’re about as green as anything else.
This isn’t being pitched because it’s “better than steel and concrete” it’s being pitched as “green” and call me a cynic but if it was actually “better” than concrete and steel and safer than concrete and steel, they would outright say that. Arbitrarily being “more green” with no other information (and being based on a material that is supposed to combust but doesn’t), is a huge red flag.