Net zero: time to think beyond site boundaries

Site boundaries: a red line that needs to be crossed

Starting from scratch, it is possible to design and construct some new buildings that are truly net zero when it comes to carbon and energy emissions. It’s a tough ask, but it has been done, albeit mainly for buildings that have relatively low energy intensity and plot density. Driving down energy demand, using on-site renewable generation and switching to electric solutions can all make a difference in carbon consumption. Buildings of one or two storeys that are not over-shadowed by other buildings can use photovoltaics to offset all their energy use, as long as the demands are at residential levels.

However, these things are not enough to achieve net zero in energy intensive buildings on constrained sites. Emerging technologies provide some of the answers. These are already improving the efficiency of chillers, lighting and IT infrastructure, and the emergence of smart energy systems is allowing better distribution of energy and the ability to store it for when it is needed. In the future, there will be transparent photovoltaic panels that can turn a window into a generator and new panels that use graphene to glean more energy from the sun.

The decarbonisation of the electricity grid in the UK also helps reduce carbon emissions and is leading to a switch to all-electric buildings. However, technology and a decarbonising grid are not going to be enough to create net zero energy-intensive buildings on constrained sites in the short term. Some red lines are going to have to be crossed.

The most important is the red line boundary around the site. To take a high-density city centre dwelling for example, it's simply not possible 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.

Developers are understandably reluctant to look beyond their site as this has the potential to add costs, risks, delays and/or contractual issues to the project. This approach 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, for example, or start to produce energy as well as consuming it. 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.

Crossing the red line between construction and operation

Unfortunately, design intent is often not being delivered in the operational performance of our buildings. This is in part because designers rarely get any feedback on their buildings after they’ve been delivered (unless something goes really wrong!). To ensure operational performance matches the ambitious targets set at the design stage, we need to monitor the performance of buildings in operation. Designers can then make suggestions to improve the actual operational efficiency – and it will also help them design better in future.

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.

Speaking to the users of buildings: the third red line

Finally, red lines between landlords and tenants should be addressed. The occupants drive the energy demand of the building, while the landlord owns and operates the central plant. This divide could be bridged with co-operation and enabled with technology. Smart meters and intelligent building management systems (BMS) can help by providing data to both landlord and tenant to inform behaviour change. It can also enable demand management to turn off equipment when it is not needed.

New thinking required

Tackling climate change isn’t something that can be done in isolation. This is true for buildings as much as it is for people: reducing our impact on this planet requires thinking about ourselves and our buildings collectively.

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.