How MMC contributes to the achievement of Net Zero

Stephen Wightman
The process for delivering Net Zero buildings is not necessarily associated with the use of Modern Methods of Construction (MMC) or Offsite Manufacturing, but the two are intrinsically linked and mutually beneficial.

In this article, I will look at how MMC and Offsite positively influence the move to Net Zero, and some of the perhaps unrecognised Net Zero benefits brought about by adopting an MMC process.

Firstly, it is important to make the point that the Net Zero piece comes in two parts – Embodied and Operational, and that they are extensively influenced by different parts of the process of constructing a building or asset. We also need to look beyond the wide-scale use of offsetting and carbon credits to achieve low or zero levels of embodied carbon and only offset what really cannot be removed from the embodied portion.

Operational Carbon

Of the two portions of the Net Zero equation, the Operational element is far more influenced by the decisions taken right at the start of the construction process and heavily by the building design. The specification of the right materials and the setting of the project Net Zero targets at the outset should ensure that all the decisions being taken through the later RIBA stages are only re-enforcing and delivering the benefits envisaged in the early stages. This also allows the setting of a realistic cost plan which is needed to take account of some of the additional costs that will be incurred to achieve the best performance (although more on the cost later).

Outside of the actual specification of the materials and systems used to minimise Operational Carbon the contribution of MMC and Offsite construction to this element can be significant. The quality control of a factory process delivers more certainty of achieving the required performance levels with low U values, integrity of insulation, and minimal air leakage. The level of design detailing and the breakdown of the building into manufacturable elements also provides a level of detail and surety and repetition about the assembly process which naturally produces greater levels of airtightness and improved building performance. Volumetric buildings have been achieving airtightness levels of <3m3/m2/hour for decades whilst the traditional building targets have been around 10.

Embodied Carbon

However, an area that is not often considered is the ability of the uptake of an MMC process to reduce the embodied carbon in the building as well.

Manufacturing processes produce less carbon in construction due to reduced levels of transportation of materials and personnel required to produce the goods. Most of the operatives will live within 20 miles of the facility and as they are travelling there every day, they are able to car share, use public transport, or even cycle or walk to work. Consequently, the number of personnel movements and energy needed to transport personnel around the country is significantly reduced along with the carbon content of the accommodation and welfare facilities normally required to house them on-site (not to mention the CO2 emissions for transporting all the temporary accommodation from site to site).

Factories can store large amounts of materials thus allowing aggregated deliveries and efficient logistics operations for the material supply chain. In addition, the same factory can build projects for multiple sites still whilst aggregating efficient deliveries from local warehouses for manufacturers.

Manufacturing processes are also much more efficient in eliminating waste as the segmented design required to assemble buildings from factory-built components tends to drive towards using full sheet sizes and being able to buy materials cut to size from the original manufacturer. Whatever waste is generated can be much more easily recycled in a manufacturing facility due to regular processes, easier access and mechanical handling, and regular long-term waste management contracts.

Cost

I mentioned cost above and this particular subject is interesting when related to MMC and the costs for achieving Net Zero. It is widely acknowledged that there is a cost uplift to achieve minimal carbon or Net Zero but from our experience, and information gleaned from a variety of projects, a proportion of this cost uplift is to actually implement the quality control processes, checks, and actual build quality required to assist in achieving Net Zero which currently comes for free with MMC and Offsite.

I believe that only when all of the above factors have been considered and the benefits properly realised should the use of PVs or other offsetting principles be applied – there is plenty we can do to actually deliver lower and Zero Carbon buildings without just compensating for poor design, construction, and processes.

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