Increased use of timber in construction is key to both meeting housing demand and being environmentally sustainable, writes Rimjhim Kashyap of the University of Galway. 

'Compared to conventional construction materials, the extraction and production of structural timber require a relatively low amount of energy'. Photo: Cygnum Building Offsite.

In our day-to-day lives, we can see the drive to reduce our own carbon footprints by using more sustainable forms of transport, reusable coffee cups and more energy-efficient appliances to name a few. In light of the recent energy crisis, we've all developed a greater understanding of the energy and cost associated with running a home.

As a result, we are seeing more and more energy-efficient buildings being constructed. If we look at the buildings we live and work in, the construction and operation of buildings contribute to approximately 37% of national emissions, 23% are operational emissions and 14% are embodied emissions.

Manufacturing of the building materials

We are familiar with the operational carbon emissions associated with the running of the building (lighting, heating etc), but we seldom consider the energy that went into the construction of the building or the manufacturing of the building materials. These are termed embodied carbon emissions and are associated with the production, transportation and site work during building construction. 

https://www.rte.ie/radio/radio1/clips/22255343/ From RTÉ Radio 1's Today With Claire Byrne, will more timber homes meet climate targets?

European and national policies have been introduced to address the operational emissions and we can see this by examining the BER rating of new builds.

There are also incentive schemes to upgrade the energy performance of existing structures to improve their performance. But while regulation has helped to reduce the energy dependency of buildings, the relative contribution of the building materials (embodied carbon) to the overall carbon footprint has increased, and strategies for reducing embodied emissions have lagged.

Research commissioned by the Irish Green Building Council demonstrated that the total emissions from the Irish built environment show a declining tendency, but the proportion of embodied carbon increased by 25% from 2009 to 2019.

Essentially, we are using high-emitting products to make our buildings more efficient and cancelling out some of the benefits. Here lies an opportunity to increase the use of timber in construction, particularly when examined in the context of the housing crisis, growing population and the significant rate of development required (about 35,000 units per year) to meet housing demands. 

A natural, renewable resource

Could timber achieve this sustainably? Timber is a natural, renewable resource that stores carbon as it grows. Compared to conventional construction materials, the extraction and production of structural timber require a relatively low amount of energy.

Furthermore, using timber products in buildings allows for long-term carbon storage in buildings over their lifespan, while sustainably managed forests continue to store more carbon from the atmosphere.

Approximately 24% of buildings currently are timber-frame in Ireland. While we don’t have a culture of building with wood, this figure is increasing, however, we are far below our European counterparts such as Sweden (90%), Finland (80%) and Scotland (85%).

For low-rise construction, timber-frame is a sustainable alternative to conventional construction and can be a significantly faster means of construction, particularly when manufactured off-site. 

How a Finnish timber frame house was erected in nine days.

In terms of larger structures, there have also been significant advances in mass timber technology such as cross-laminated timber, glued-laminated timber (glulam) and laminated veneer lumber. Cross-laminated timber is a robust multi-layered engineered wood panel with a high strength-to-width ratio and has received the most attention.

Cross-laminated timber building systems

Cross-laminated timber building systems are prefabricated to a high degree of accuracy, and easily erected in a low-dust, low-noise assembly with minimal site waste, reduced labour, and rapid construction times.

These high-performance wood products have now been used in a range of building applications and even multi-storey construction up to 81 m tall, taller than any building in the republic (Capital Dock (79 m)).

In Ireland, the use of products such as cross-laminated timber has been limited largely due to restrictions on the use of timber within our current building regulations.

The Timber Engineering Research Group at the University of Galway has spearheaded the research using Irish-grown timber to manufacture cross-laminated timber and found it compares well with commercial panels manufactured in Europe. 

To further address the current barriers, this group is currently engaged on two projects. One focuses on examining the use of Irish-grown timber in the manufacturing of engineered wood products for modular construction, while the other looks at establishing reliable data on Irish-harvested wood products to better predict the environmental benefits of using Irish-grown timber.  

The findings will demonstrate that the use of locally grown materials can reduce embodied carbon emissions in the construction industry. Increased use of timber in construction is key to meeting the housing demand, while also being environmentally sustainable.

Author: This article was written by Rimjhim Kashyap, University of Galway. She is a PhD researcher with the Timber Engineering Research Group in the School of Engineering and Ryan Institute at the University of Galway. This article first appeared in RTÉ Brainstorm.