I am also deeply skeptical of the net-negative claim, mostly because of the outsized role plywood appears to play in the building productions demonstrated. There are several energy-intensive steps required to manufacture plywood that are not present with standard lumber production. Additionally, transport overhead is higher due to the comparative rarity of the specialized mills used to create plywood. Unfortunately I haven't been able to find any kind of real numbers comparing the carbon footprint of lumber vs plywood to demonstrate exactly how much more carbon it takes to manufacture plywood vs lumber.

FWIW, plywood (OSB, chip board, etc) are already heavily used in house building. Floors, roofs, sheathing, etc.

Yep. And as stated by others upthread those houses are mostly designed to last about as long as OSB does under normal conditions.

I am also skeptical but I would not call the claim bullshit. Building from wood could in theory be carbon negative. Unclear though if this process is.

Another thing worth considering is that building small houses uses a lot of land, land which might have had forests. That needs to be considered too.

I've explained why pretty clearly. Trees are not a renewable resource in the context of climate change. They take dozens of years to grow, they are part of an biodiverse ecosystem, and just cutting down forests has a much bigger effect on the ecosystem and its carbon sequestration capacity than the tree alone. And don't get me started with tree farms.

This carbon negative claim taken to the extreme would mean, that we should just cut down all trees and plant new ones. I think you can see why this is ridiculous?