Not too tall, not too short, but just right.
Tall wood buildings are all the rage these days, but this TreeHugger has been wondering if we shouldn't be really be thinking differently about it, and instead of doing technical gymnastics to go tall, we should be concentrating on building for that "missing middle" as Daniel Parolek called it, or the Goldilocks Density, as I call it.
Being tall is wood entire reason for existence. Literally.— Topher Belknap (@Green_Fret) February 17, 2018
Not everyone agrees with me, and this tweet response makes a very good point. But what works for a tree in the forest is not necessarily best for buildings. That's why I like this new student residence in Marseille, designed by A+ Architecture, which at this time is one of the tallest wood buildings in France at eight storeys.
The Lucien Cornil Student Residence was built out of wood for all the usual reasons, according to ArchDaily:
The use of solid wood CLT (Cross Laminated Timber) limits energy consumption and provides an excellent carbon footprint. “The entire building has been designed to be very heat and acoustically efficient, while maintaining consistent lines and at a very competitive price,” states A+Architecture.
But another reason for using wood is that it goes up quickly, with less disruption. While this building has concrete cores for the stairs and elevator, the rest of it is all big panels of CLT that can be installed very quickly.
In this constricted urban environment, the choice of wood construction was obvious. Reduction in disruption caused by the works, an optimised schedule, but also a commitment to the comfort of the residence are what convinced the CROUS to embark on the adventure.
We have also noted the biophilic, calming effect that comes from being surrounded by wood.
Wood is found on all the ceilings and on the walls of the rooms, the latter being sound-proofed. It is also present in the corridors and communal rooms, but not on the facings where its ageing is deemed too visible. Its strong interior presence gives the impression of a warm and relaxing atmosphere with soft acoustics. The wooden shrouds, with cross-laminated assembly, give off a forest scent.
They have used a more durable metal skin for most of the exterior, with some wood highlights.
The higher one builds, the tougher the fire codes become. Here, at eight floors, they were able to leave a great deal of the wood exposed, whereas when you look at the Brock Commons TallWood student residence in BC, the wood is buried behind drywall.
We have noted before how wood actually can perform better than steel in a fire, because the char that forms acts as an insulator. So if you design the columns and beams to be larger than they need to be just for structure, a sacrificial layer turns into non-combustible char, protecting what is underneath.
I did find it surprising that there do not appear to be sprinklers, just heat detectors.
At eight stories, the architects don't have to worry as much about wind loads. They only need one elevator to service 200 units, because the students can get a bit of exercise walking. They apparently don't even need sprinklers. There are a lot of advantages to building at the Goldilocks Density: Not too tall, not too short, but just right.