Canadian cities take wooden skyscrapers to new heights | Hacker News Reader

Canadian cities take wooden skyscrapers to new heights

theguardian.com

42 pointsperfunctory23 comments

They glossed over the “wood is viewed as fire prone” thing and I can’t find the article posted to HN a few months back which discusses it further. The gist was wood protects itself with an insulating layer of charcoal as it starts to burn, and it maintains its strength when heated much better than steel, which starts to bend and cause a cascade failure.

this one? https://news.ycombinator.com/item?id=20058485

Modern glulam (glued laminated timber) and cross-laminated timber beams are really good. Formaldehyde emissions are under control. Fire resistance is surprisingly good. Economical and less energy needed for manufacturing.

Plus it sequesters carbon

Note that the Brock Commons mentioned in the article is a bit of a hybrid as the structural core is a pair of concrete stairwells.

Norway's Mjøstårnet however (which took the palm from Brock) is structurally fully wooden, concrete is only used as stabiliser for the upper stories (inbetween the upper 7 stories to limit swaying), it's not load-bearing.

Are you sure this is the structural core and not simply how they built the fire exit and satisfied the municipality that the material for this fire exit is non combustible? I doubt this is structural.

The reinforced concrete cores at Brock Commons are engineered to resist sheer during earthquake and wind events. [1] BC is seismically active and every tall buildings experiences non-trivial wind loads.

[1]: https://www.structuremag.org/?p=11624

In Europe you will still find plenty of wood construction roadblocks. Personal experience : in Belgium a wall that is placed on your terrain edge is considered a common wall and cannot be made using wood.

That's generally true in the US as well. The placement of combustible walls relative to property boundaries is constrained by building codes to mitigate the spread of fire via radiant heat from fire on the adjacent property/building.

Area separation wall systems [1] are about as close to "wood on the property line" as is allowed. But technically the gypsum board is the wall between structures (and for practical purposes both structures need to be built at the same time).

[1]: http://www.usg.com/content/dam/USG_Marketing_Communications/...

I just hope they also go with green roofs. They make the microclimate within cities just so much more sustainable.

For someone who are knowledgeable about using wood for large buildings: how does it stack against the weather?

I live a few miles from the largest in Norway[1], and if I recall, it's all exposed. Perhaps some protection is added as of late. However, I also know that using oil-based paint on the cladding increases the risk for rot if water gets trapped inside. How do you need protect exposed wood for centuries to come..

[1]: https://en.wikipedia.org/wiki/Mjøstårnet

Humans have thousands of years experience with wood and weather. Traditional wooden building withstands weather and rot quite well when you take care of the building.

Modern wood materials can be very technical and require less care. I would imagine that the exterior walls are heavily treated. Pressure-treated lumber can be very rot resistant. How resistant depends on how much you add chemicals. Wood can treated so that it's not rotting in direct contact with water and soil if needed. Modern preservatives are have soluble copper in them. Antimicrobial properties of copper are well known. If you pressure treat wood with these preservatives microbes don't rot them.

As I recall, you got some old wood buildings in Norway already, how are they maintained?

A lot of traditional buildings around that area were/are treated with wood/pine tar and charcoal, or by slightly burning the outside for a cheaper and easier but less effective treatment.

Anybody knows what the sound insulation are like in these?

Architects usually specify to include a sound dampening material on each floor.

I wonder if we could genetically modify the trees to be more construction friendly.

It would be neat if you could plant a seed and it would automatically grow into a house.

What is the environmental impact of cutting down trees and constructing so many buildings with wood?

As long as the forests are replanted, likely benifit is carbon sequestration. We should avoid logging old-growth forests since they provide ideal habitats to deer and other animals. But logging second growth forests can be environmentally sustainable.

It captures the carbon and lets new trees be planted where the old were. This sequestration is a small win for the climate, and a huge net positive compared to building with steel and concrete.

Surely much lesser and more sustainable than concrete and steel?

How does this handle pests, like termites?

As a Vancouver local, I can't recall ever hearing about termite damage. I don't know if we have them here. I've heard a few cases of carpenter ants eating walls.

Woodpeckers can be a problem -- they will occasionally try to nest in the side of a house. They also like to peck on metal siding. I think they do it to attract mates?

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