Build Back Better Part 2

Is MMC the answer?

20 October 2020

The 2019 amendment to the Climate Change Act 2008 outlined the UK government’s commitment to reduce all greenhouse gas emissions to net zero by 2050.

At Ayre Chamberlain Gaunt we strongly believe that the creation of high-quality, low energy and low embodied carbon architecture can only result from multi-disciplinary collaboration from first principles. Sharing experience and knowledge about strategy, design detail, delivery and in-use is key to developing the most appropriate, sustainable and fabric first project solution.

So, how can we as an industry deliver on the 2050 target?

The Climate Change Emergency and delivery of 2050 carbon neutrality will only be possible in construction through an acceleration of initiatives such as the Future Homes Standard and substantial retrofit of existing stock over the next 10 years. The domestic Green Homes Grant is a start but as with the Future Homes Standard, it needs to go much, much further.

In their recent London Climate Action Week ‘Getting to Net Zero’ webinar, The Passivhaus Trust and LETI outlined that to achieve the 2050 target, rather than the £5bn spending allocation defined recently, £45bn is the sum actually required per annum (UK Committee on Climate Change, 2019). LETI’s Climate Change Design Guide and Embodied Carbon Primer, the Architects Declare movement, AJ’s RetroFirst Campaign and the RIBA Climate Challenge 2030 go beyond operational carbon, looking at embodied carbon. RIBA’s Climate Challenge 2030 aims to assist meeting whole life carbon (operational and embodied carbon) for new and retrofitted buildings by 2030.

How can MMC help?

The RIBA’s Plan of Work 2020 revision, which now integrates MMC’s delivery, is a good start. MMC has the potential to deliver sustainable, high-quality architecture, quickly and efficiently. It reduces waste when compared to traditional construction methods due to limiting variants, leading to opportunity for greater cost certainty in estimation.

The Ministry for Housing Communities and Local Government published a definition framework in 2019, outlining seven categories for MMC. 1 to 5 being off-site and near site pre-manufacturing and 6 and 7 being site-based process improvement, along with 7 material genres. There are multifarious sub-variants when these categories and material genres are combined and therefore differing potential for addressing both operational carbon and embodied carbon performance, tailored to a project’s scale and constraints. Resultant strategies could include on-site flying factories or off-site manufacture, for example.

Image: Ayre Chamberlain Gaunt’s work with Low Carbon Construction – Offsite/OnsiteTM – The Flying Factory

MMC generally offers the opportunity to reduce the performance gap through factory-controlled manufacture, to address whole life carbon (operational carbon + embodied carbon). Operational carbon refers to the CO2 and other greenhouse gases which are emitted as a result of a building’s energy use. A new building that meets net zero operational carbon is 100% powered by renewable energy. Embodied carbon relates to the emissions associated with extraction, manufacture, assembly and construction, as well as the in-use or maintenance stage and the end of life stage. Carbon or climate positive development means going beyond achieving net zero carbon emissions, creating an environmental benefit by removing additional CO2 from the atmosphere. As with many Climate Change solutions, restorative design that learns from and works with nature should be the actual goal.

How can MMC increase the delivery of suitable new build housing?

MMC options are very well suited to the delivery of low energy and net zero new builds. Passivhaus is the only standard that guarantees performance for energy, comfort and construction excellence, resulting in buildings with dramatically lower operational energy. This leads to less energy generation being required meaning the approach is a highly cost-effective baseline on the quest to meet in-use zero carbon.

Inclusion of on-site renewables over this baseline means opportunity for energy positive developments via the Plus and Premium Passivhaus classes. Factory fabrication enables the airtightness and moisture tightness Passivhaus requires. Combined with the use of a high-performance mechanical heat recovery ventilation (MVHR) units, this leads to improved indoor air quality and comfort for occupants.

However, with improved thermal performance, integrating suitable levels of thermal mass during MMC fabrication is paramount to meet the CIBSE TM52 and TM59 overheating future weather file or beyond, meaning retrofit measures shouldn’t be required to achieve resilient performance in the future.

Concerning, however, and as outlined by John Palmer of the Passivhaus Trust, is the fact that any house now not built to Passivhaus levels of performance as a minimum is likely to require retrofit prior to 2050, therefore current developments are adding to the burden. He summarised that to meet the 2050 target, if retrofit of the built stock commenced from the beginning of January 2020 through to December 2050, that’s the equivalent need to retrofit one home every 35 seconds. We are quite some way from achieving this in the UK, and are increasingly falling behind.

Could MMC be a solution for retrofit as well as new build?

Innovative MMC methods should also be seen as a solution for retrofit, whether meeting Passivhaus, EnerPHit or Energiesprong standards. For example, with the latter endorsing pre-manufactured panelised envelopes over existing properties. However, these standards are not enough alone to meet zero carbon, as there is no restriction on the materials to be used and the associated embodied carbon. There is an opportunity to tackle both operational and embodied carbon when MMC is considered from first principles and best practices are drawn from post occupancy evaluation (POE). This will also help to create an industry that perpetually becomes more economically viable, in a quest to go beyond and be restorative, rather than achieving neutrality.

Meeting policy requirements is one thing, however, typically at present we are having to rely on the voluntary morality of pioneers trying to go beyond. However, it is the client and designer’s choice to select materials appropriately, using guidance outlined above and material Environmental Product Declaration (EPD).

How can we encourage a mindset change?

To take advantage of MMC in the quest for zero carbon requires a mindset change from ‘constructing’ to ‘manufacturing’. Utilising low embodied carbon materials in this process and where possible, aligning to circular economy principles such as McDonough and Braungart’s ‘Cradle to Cradle’ aspirations, will enable construction for disassembly. Materials are viewed as nutrients circulating in healthy, safe metabolisms. Combining this with learning from the automotive industry, for example, the use of ‘Just in Time’ (JIT) manufacturing, the potential benefits in refining material application, time, cost and quality will be improved.

MMC is just designing and building differently, with improved performance and efficiencies. As a practice, we believe that MMC offers great opportunities in finding essential solutions for closed loop cycles and circular economy when combined with a rise in digital design and construction techniques, including project BIM integration and enabled fabrication.

Maybe the industry will continue to wait for policy to be implemented or perhaps, feeling the affects of the growing importance of health and wellbeing over recent months, briefs will be challenged to take advantage of the prosperous growth opportunity a greener economy can provide. MMC certainly has an ever-increasing role to play, and will perhaps enable the construction industry to lead the way on the path to net zero.

– Paul Avery, Senior Architect

TAGS Sustainability

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