Timber and concrete can be used harmoniously in construction projects.
Bill McKay, a senior Lecturer in the School of Architecture and Planning at the University of Auckland, argues that New Zealand should use more composite materials in construction projects.
“A timber and concrete structure,” he said, “which is the best of both worlds.”
Speaking to Radio New Zealand’s Nine to Noon host Susie Ferguson, Professor McKay discussed the positives and negatives of concrete and timber.
Bill McKay is an active writer and contributor to New Zealand architectural history. In addition, he works as a Sustainability contributor for RNZ and a columnist for Architecture NZ.
Mr McKay strongly supports engineered wood products, “New Zealand construction’s future.”
“Think of plywood on steroids,” Mr McKay said, “it is precision made, which means that they are dimensionally accurate and can reduce waste.”
According to McKay, heavy timber can be earthquake and fire-resistant and “outperforms steel as it charrs on the outside and does not burn through.”
However, McKay said, concrete is also an important material often misused in New Zealand.
McKay says most New Zealand concrete buildings must be better oriented to the sun.
Concrete, like timber, has a thermal capacity, “which means it can store heat.”
“The great advantage of concrete slabs is that when we use them for passive heating, if oriented to the sun,” according to McKay, is that “they can store that day’s warmth from the sunlight (…), and they can re-radiate the warmth into the house.”
McKay said concrete buildings are also popular in the tropics, “if you keep windows smaller, the reverse happens, and it can keep structures cooler.”
The big problem, however, is that concrete has a much larger carbon footprint than timber.
“This is one reason why architects choose not to demolish concrete buildings.”
Through a process known as retrofitting, “architects are stripping buildings back to the bones, the concrete structure and then redeveloping them back to modern standards,” McKay said.
70% lower climate impact by combining mass timber and concrete
In April, Wood Central reported on a new hybrid material developed by Metsä Wood, combining both materials to offer enhanced strength, durability, reduced weight and carbon footprint.
The so-called sandwich component is ideal for exterior walls, providing heightened resistance to weather and wind.
It uses Metsä Wood’s Kerto LVL Q-panel as a load-bearing core panel and an external Heidelberg Materials’ climate-enhanced concrete panel.
Jussi Björman, business director of construction at Metsä Wood, explains,
“By developing a hybrid element, we want to see how the different technical properties of wood and concrete can work together to support each other in building structures.”
Björman added, “Our joint development work is a step forward to find new ways for the construction industry to continue building sustainably and with an even lower climate footprint.”
Research: Hybrid timber systems could be the new reinforced concrete
The collaboration agreement between Metsä Wood and Heidelberg Materials Precast Contiga means that the companies are now starting joint development work of a competitive hybrid element.
In March 2022, researchers at The Fraunhofer Institute for Wood Research at Wilhelm-Klauditz-Institut set up a research project looking at the long-term value of combining timber and concrete into hybrid building systems.
The team has devised a new approach for combining timber and concrete mechanically using steel nails, plates, and nets.
According to Prof. Libo Yan, Senior Scientist and Junior Research Group Leader:
“By bonding the materials with polyurethane or epoxy resin, we can reduce the weight of the timber hybrids and hasten the manufacturing process by up to 15%.”