Making the case for wood construction

Wood is one of the few renewable building materials, and new technologies like Cross-Laminated Timber (CLT) are letting architects and engineers do bigger and taller buildings, using massive wood elements built up from plantation wood "grown like Christmas trees." Engineering giant ARUP is doing really interesting things with wood, described in Timber offices: the time has come. They note its benefits:

• Timber is the only 100% renewable building material
• Timber locks up carbon for the life of the building
• Because it’s a cellular material like bone, wood is strong and light
• This lightweight cellular structure also makes wood a natural insulator
• Easy to prefabricate and transport, timber makes for quick construction
• Timber is attractive and can be left exposed, reducing the cost of finishes

A big worry about wood, that has limited its use until recently, was the fact that it can burn. Timothy Snelson of ARUP explains that the new massive CLT and glulam elements are different; they are hard to get burning, noting that "you don't start a fire with a log, you start it with bits of kindling." He says in a video in the Arup post that "we know the rate at which timber burns, this is established from lab tests, So as engineers we can simply calculate the amount of wood that will be lost in the fire and we make the beams bigger by that amount of lost timber."

This is disputed by some, who send me tweets like this one that mention the University of Nottingham fire last year.

@lloydalter admirer of @TreeHugger but charring of burning wood didn't protect this @nottinghamuniv CLT lab last year pic.twitter.com/yzjcJp296S

— World Concrete Forum (@WorldConcreteF) May 13, 2015

However this fire started during construction, when there were no windows and doors installed. According to the fire department,

At this stage of the construction, without fire doors or in some areas glazing, there were open voids between floors. Whilst services were being installed and commissioned this caused the building to be self-ventilating and once the fire had taken hold it then passed through the building rapidly and with some ferocity.

The problem of fires during construction of wood buildings has been discussed before; it is clearly an issue of concern. But it's not a reason to write off wood construction; the environmental benefits are considerable, as this graphic from Arup demonstrates: