True net zero carbon buildings means crossing some red lines

True net zero carbon buildings means crossing some red lines
Published on September 27, 2019
Dave Cheshire
Dave Cheshire
Regional Sustainability Director at AECOM
12 articles
The Government’s commitment to zero emissions by 2050 sets a huge challenge to the construction sector and one that we all need to embrace if we are to help address the climate crisis. The Committee on Climate Change proposes eradicating burning of fossil fuel in all new buildings by 2025 and the latest Intergovernmental Panel on Climate Change (IPCC) report concludes that “New construction [has] to be fossil-free and near-zero energy by 2020”.[1]

Designing and constructing new buildings provides a one-off opportunity to create truly net zero carbon and energy buildings, meaning that we have to balance the net demand with renewable energy generation. This is a tough ask, but it has been done, albeit mainly for buildings that have relatively low energy intensity and plot density. To achieve net zero in energy intensive buildings on constrained sites, we have to do the obvious stuff like driving down energy demand, using on-site renewable generation and switching to electric solutions, but we also have to cross some red lines:

Firstly, the red line boundary around the site will have to be straddled: it is unlikely that sufficient energy can be generated on site to offset the energy demand of the building, so there will have to be some contribution from beyond the site boundary.
Secondly, the landlord / tenant divide will have to be erased: the occupants drive the energy demand of the building, while the landlord owns and operates the central plant.
Thirdly, the line between construction and operation needs to be bridged so that operational performance matches the ambitious targets set at the design stage. All too often, the design intent is not being delivered in the operational performance of our buildings.
Developers are, understandably, reluctant to look beyond the site boundary for a new development as this has the potential to add costs, risks, delays and/or contractual issues to the project. This has already changed in London with the London Plan’s energy hierarchy that requires developers to investigate sources of ‘secondary heat’, such as sewage heat recovery, canals, rivers, and district heating systems. The net zero ambition will drive developers and building owners to find places where they can install photovoltaics on neighbouring buildings or other parts of their portfolio and start to produce energy as well as consuming it – becoming ‘prosumers’. This would allow constrained, energy intensive buildings to glean renewable energy from lower intensity buildings with large roof areas (industrial buildings, stations, etc.) to help them towards net zero.

The landlord / tenant divide can be bridged with co-operation and enabled with technology. Smart meters and intelligent BMS can: integrate different building control systems (such as landlord and tenant’s BMS); provide data to both landlord and tenant to inform behaviour change; and enable demand management to turn off equipment when it is not needed.

The differences between design intent and operational performance can be reconciled by using ‘digital twins’ to provide better estimates of operational performance at the design stage and help to understand how the building should be performing in operation. And there are lessons to be learned from the way that Passivhaus projects are delivering impressive performance by setting ambitious targets and applying a high level of scrutiny to every detail.

The road to net zero buildings requires us to cross both physical and contractual boundaries that have long hampered our ability to deliver low energy, low carbon building. We can only achieve net zero in our densely populated buildings on constrained sites by breaking down these boundaries and using disruptive technologies to dissolve the lines we have drawn.

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