A modern methods of construction (MMC) approach has many benefits, such as reduced construction waste, labour costs, quality issues and construction timelines. Here Mohannad Altabbal, customer success manager at Graphisoft discusses the benefits of using different materials for MMC construction.
Time for timber
In the UK, concrete, steel and masonry are firmly established as the materials of choice for construction. One of the things that an MMC mindset looks at is improving existing approaches or looking for new alternatives.
Take timber for example. Timber is often seen as a specialist material for construction, but this should not be the case. In December 2023, the government published its Timber in Construction Roadmap, outlining its commitment to increasing the use of timber in construction as part of its efforts to meet its net zero target.
As outlined in the roadmap, one of the main benefits of using timber for construction is carbon reduction. Each building’s carbon impact is made up of operational carbon from heating and energy usage and embodied carbon from manufacturing processes, maintenance and end-of-life disposal. The roadmap explained that the use of timber can reduce the embodied emissions in a single building by 20% to 60%.
Where timber has been harvested from sustainably managed forests, it acts as a carbon store, which helps offset the carbon impact across a building’s lifetime. Carbon storage is approximately 50% higher in timber framed homes than in masonry homes and can be up to 400% higher for larger buildings that use engineered timber products such as cross-laminated timber (CLT) instead of concrete, according to research led by the BioComposites Centre at Bangor University.
Engineered timber goes a step further by optimising the raw material to remove natural weaknesses and enhance natural strengths. Some engineered woods are pound-for-pound stronger than steel with the same carbon-saving advantages as standard timber.
An example of the versatility of wood can be found at The Centre for Advanced Timber Technology (CATT), which was designed by Bond Bryan using Archicad to create a purpose-built facility to demonstrate advanced timber technologies and teach the next generation of engineers.
Designed using DfMA (Design for Manufacture and Assembly) principles, the timber and steel panels, frames and beams were manufactured offsite before being delivered to site for assembly. The timber frame was also designed so that it can be dismantled and re-used in the future.
There are several types of engineered wood, but the ones used most often for large structural elements in the UK are: glued laminated timber (glulam), cross-laminated timber (CLT) and laminated veneer lumber (LVL). CLT can be used for load-bearing beams or cut into wall panels with spaces for doors and windows pre-made. It is also ideally suited for wall and ceiling cassettes due to its insulating properties, which can then be transported to the site pre-assembled.
One good example of how CLT can be used on a larger scale project is at Sugar House Island. Designing in Archicad, architect Waugh Thistleton retrofitted two historic buildings using CLT to extend existing concrete and masonry structures.
Renovations included work on a five-story masonry warehouse and a Victorian print warehouse, including extensions and new internal structures created with CLT, while the façade and character of the buildings were maintained.
Supporting steel
There are many different types of steel that all have their own benefits and uses, but one common solution for MMC buildings is light gauge steel.
Compared to heavier forms of structural members made from hot rolled steel, light gauge steel offers significant advantages both economically and structurally. The lighter weight allows the steel to be easily transported once the MMC components are manufactured, which can make it more attractive for businesses with a lower budget.
Light gauge steel is also an excellent thermal insulator because it is very airtight. Heat transfer is reduced, allowing the internal temperature of the completed MMC building to remain consistent.
This consistent temperature consideration helped McAvoy to deliver a steel-framed MMC building, Merstham Park School. Designed in Archicad to accommodate 900 pupils, a key requirement of the project was to create a school with significantly reduced energy demand.
The steel MMC structure was made from 178 modules that were transported to the site and craned into place in just six weeks. This process helped keep noise and disruption to the pupils attending the temporary school on the same site to a minimum – and ensured a fast delivery. A combination of digital technology and modern methods of construction enabled the reduction of the school’s operational energy consumption by more than 73%.
Another benefit of light gauge steel is it is easy to recycle at the end of the building’s life. Steel production requires large amounts of energy, but when steel is reused or recycled, this reduces the overall amount of energy needed for manufacturing new materials. Moreover, steel can be easily traced throughout the lifespan of the project to ensure all materials used meet the required specifications and standards for the building project.
The best of both
Hybrid structures combine timber with steel or concrete to take the best qualities from each material. Moreover, pre-fabricated MMC panels are frequently made up of layers of different materials to provide structure, insulation and fire-proofing.
Research from the University of Cambridge and Edinburgh Napier University found that embodied carbon can be reduced by almost half when using volumetric MMC systems.
Free carbon calculators enable architects to assess the carbon impact of different materials and discuss these options with stakeholders. By combining these calculators with architectural software, like Archicad, architects can ensure all stakeholders understand the impact that design decisions will have on the carbon impact and performance of the building.
By combining the benefits of timber and steel, MMC can continue to compete against more traditional forms of construction on sustainability and cost measures and expand into the broader construction industry far more quickly.