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Green technology: designing for low carbon

May 2021

Written by Damon Schünmann, Strategic Consultant at Barbour ABI

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        With the construction industry and the built environment being major emitters of carbon, reducing embodied as well as operational C0₂ in new-builds have become paramount twin goals for designers.

        Consultant Aecom, like many of its peers, has been working on solutions that might give countries such as the UK any kind of shot at achieving publicised net zero ambitions. Regional director Adam Parkes explains that part of the problem for new-builds in the residential and commercial sectors is heavily front loaded into the construction phase. He says the embodied carbon of a typical building’s fabrics are still responsible for around 70% of its overall emissions, even when viewed over a 60-year operational lifecycle. Clearly this spike at the very start of a building’s life needs to be better controlled.

        As part of this drive, Aecom launched its Sustainable Legacies Strategy in April and one of the four pillars of this is something it calls ScopeX, which is an initiative to reduce carbon through design that considers embodied and operational C0₂ across the entire project life cycle. The ScopeX approach takes into account materials, site locations, logistics and construction methods to reduce the impact of projects on the natural environment.

        This push has seen Aecom develop a new digital tool to make inroads into that balance between embodied carbon and the operational efficiency of a material. Along with this is an increasing focus on a building’s geometry with a ‘form factor’ score – generally falling between 0.5 and 5 – denoting operational carbon efficiency. Here, a lower number indicates a more compact and carbon friendly building in terms of heat-loss.

        New design tool

        “A key aspect of our ScopeX launch is about calculating design approaches and this tool is part of that,” says Parkes. “It’s a conceptual embodied carbon optioneering design tool; we’ve released it to clients and it will be launched very shortly on social media platforms. From a structural engineering point of view we need the best form for reducing construction materials and what we’ve tried to do is to find that balance [between embodied carbon and operational efficiency].

        He says that to create this tool has required the business to invest heavily in terms of money, time and resource to pull together a database of vast swathes of structural engineering answers and solutions for building designs. This provides options that allow a user to play with elements such as column spacing, number of bays, building area, from which it then generates carbon output. “This is purely for structural fabric and embodied carbon – that 70% piece,” he says. “But the key question is ‘how does this interface with the operational side?’

        “What we’ve tried to do within Aecom’s sustainability team is look at form factors and use case studies of different types of buildings – how they perform from an energy perspective – and then look at the relationships between material consumption. We can then start finding trends and optimum building heights and shapes to try and get us towards that net zero agenda.”

        Aecom principal engineer Maged Hanna explains further. “The form factor of the building looks at how many sides are exposed because it’s all to do with the heat loss. The operational piece looks at how much of this heat loss needs to be conditioned, so effectively form factor is what the shape is and what its adjacencies will be like. It basically produces a ratio between the building’s envelope and the net floor area and how much of that is actually exposed. “The deeper the building is [away from the facade], the less of it is going to be exposed, however you’ll probably then need more lighting energy because there’s less daylight penetration,” he says.

        Searching for the Holy Grail

        The tool includes geotechnical, cost management and engineering. “It’s a system where you can put a location in,” says Parkes, “so if I put in Aldgate Tower, which is the Aecom [London] office, it draws from the Google geo-referencing database to our nearest project with a borehole log (an assessment of what the local strata is comprised of), to give us some material estimations for foundations as well.

        “Our cost team have priced the quantities so clients will have an expectation on cost inflation,” he adds. “They can use the lowest carbon solution, but they also have some gauge on what’s the cheapest and most expensive, or somewhere in the middle. What we’re trying to do is answer that holy grail of what is the best choice of material and the best form of a building. We can interface that down to this tool where the client can draw the shape of building’s footprint, and there’s a cost graph and a carbon graph so they can play around with slide rule bars for column grids, steel, concrete or timber and it will give you that estimation”.

        Design evolution
        Meridian Water is a £6bn, 20-year residential regeneration programme for 10,000 homes in Enfield, North London. Here, Aecom Sustainability, Structures, MEP and Cost Management are supporting Assael Architecture with the “rightsizer” concept where it has been allocated random sites within the wider Meridian Water to pull together a roadmap on how to meet the ambitious LETI/RIBA 2030 carbon targets. Here, Aecom is considering the design for a provisional, unapproved 16 storey residential building as part of the overall consented master plan.
        “We’re working for Enfield Borough and they have asked us to estimate the carbon footprint against their 2025 targets,” says Parkes. “If we’d designed it as we would have done three or four years ago it would probably be nowhere near. They’re aiming for 600kg of C0₂ per square metre and what we’ve done by thinking differently is get to that target by omitting every other floor.” Theoretically at least, the approach appears to be paying off.
        “We’re building 6m storey heights instead of 3m, and each intermediate floor will be formed in timber or another lightweight structure. What we’ve done is ensured the stability of the building by just making the primary shell larger spaced as you go up,” he says, “and we’ve made it lighter by using a substitution material for each intermediate floor – plus there’s less carbon in the [reduced requirement] foundations. We’ve managed to get to that target but it is a challenge.”

        For this article I also spoke to Eszter Gulacsy who is technical director sustainability and healthy buildings at Mott MacDonald. She agrees that experimenting with new-builds is a good way to push the low carbon envelope, but adds that looking for C0₂ reduction in this sphere should be viewed with a sense of proportion. She says that while they are great platforms for innovation, reducing their carbon footprints will never be the biggest mitigation for achieving net zero goals. “Buildings are these little jewellery boxes compared to [say] train lines, in terms of complexity, but also agility,” she says. “So if you look at how long it takes to design and build a building, it’s an order of two to five to 10 years, where infrastructure might take 25 years.

        The incubators of innovation

        She outlines how buildings provide more options to experiment. “It’s almost like they are the incubator of a lot of ideas because they also have shorter life cycles and they’re also more complex; you have your structures, your M&E and your occupants. You could imagine it like a pocket watch with all these moving parts, this is what buildings are in the construction world compared to the infrastructure side of things,” she says. “[But when it comes to low carbon impact] the differences that you can make on the infrastructure side are so much bigger, and the stakes are so much higher; that’s where the real difference comes.”

        But while a dogmatic focus on low carbon buildings clearly remains part of the solution to the low carbon jigsaw, Parkes points to another role that the Aecom tool may be able to play. This, he says, is around re-prioritising the design process. “At the moment there’s an issue in the UK where engineering comes later in the process than it probably should,” says Parkes. “So what we’re trying to do here is educate the industry that engineering should probably determine the form and shape of the building, not the architectural aspiration. I think visual aids like this can show that if we are interested in carbon, why don’t we show the architect what the shape could be on that site and we work around that?

        Bridging the occupancy carbon gap

        It’s well known that an expanse exists between the designed performance of a building and it’s real-world figures that largely result from how it’s operated. But how can those dots be more effectively joined? “We have some very talented modellers and we can model buildings to death, however how is it actually operated?” says Hanna. “A lot of the data we get doesn’t really match the modelling and it’s a data overload [in any case]. That’s why we need to standardise which data we extract from these buildings. When you’re looking at your BMS [building management system] you’re not actually getting all the data you need; you’ll have an abundance of one source but a lack of another because there isn’t a standardised solution to this. He says the industry must start to build for [real-life] operation. “You need specialists that can actually calibrate buildings in the same way that we’re designing them and I think this is the gap that every consultancy is [trying to contend with] at the moment,” he says.

        Help from down under

        Simon Law is Aecom associate director. He points to help that has arrived from the far side of the globe with a new system of post-design, occupancy carbon measurement that may be about to make a difference. “We’ve had Digital Energy Certificates for ten years, but the government hasn’t enforced it within the private sector,” says Law. His focus is on ‘NABERS’, an Australian operational energy scheme that the BBP (Better Buildings Partnership) has introduced to the UK. “The big developers have forced this issue and brought in NABERS which has then forced BREEAM to copy it and now you’re seeing [building regulation] Part L saying ‘thou shalt forecast the operational energy of your building’,” he says. “It makes the MEP guys put their necks on the block and we’re not going to do that without demanding the contractor puts his on the block as well – that’s a big shift. We’re starting to see all these jobs where the client is demanding NABERS which says you must meet a post-occupancy energy target.”

        The BBP has now handed NABERS over to BRE and the scheme officially launched last November. “We’ve been working on a building which is going through NABERS and just about every new high-spec office that we’re doing now seems to be looking into using the NABERS UK scheme,” he says. “That is what’s going to force the whole post-occupancy [situation] by holding people like the MEP guys and the contractor accountable. Rather than us running for the hills after practical completion, it’s going to tie us in to RIBA Stage 7,” he concludes.

        While there is no silver bullet to achieving net zero new-builds, and effectively addressing vast swathes of existing estate must remain a major priority, initiatives such as these are at least collectively pulling in the right direction.

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