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Feature www.thefis.org 19 Defining net zero carbon For the purpose of this paper, we consider a net zero carbon building to be one where the embodied and operational carbon emissions have been assessed and reduced to the greatest extent possible, considering the whole building life cycle, and where the residual emissions associated with at least the construction works and operational energy use have been offset. The key findings from the case studies featured in the paper 1. Net zero carbon is being delivered through both retrofit and rebuild approaches, and whole life carbon assessment (WLCA) is being used to determine and/or validate the approach pursued. Buildings that are targeting net zero carbon in construction and operation are being delivered through both retrofit and redevelopment of central London’s 20th century commercial stock. 2. Developers are increasingly adopting a ‘retrofit first’ approach and only pursuing other strategies where retrofit is not viable. Schemes that involve full or partial redevelopment tend to do so after exploring retrofit first. 3. Retrofit ismost often viable for buildings that present a specific set of characteristics, whilst redevelopment ismost often pursuedwhen these characteristics are not present. Retrofit is most often viable for buildings that present overall good architectural quality, with a robust structure and foundations with sufficient load bearing capacity to support extensions. Buildings that are of poorer quality construction, have an insufficiently robust structure and/or unadaptable layouts present greater technical difficulties and less potential to unlock additional commercial value through retrofit, but can effectively achieve net zero carbon (in addition to economic and social benefits) through a redevelopment approach. 4. Retrofit and redevelopment projects employ a plethora of measures to reduce whole life carbon, from the reuse of existing structures to specifying all-electric, renewables based energy systems. Retention of existing foundations and structures, façade refurbishment and building systems and equipment upgrades are most important for retrofit. On redevelopment schemes, reusing demolition materials and other low carbon products along with modern methods of construction reduces upfront embodied carbon, and there is generally flexibility to explore a wider range of passive and active design measures to reduce operational energy demand and adapt for future climatic conditions. Developers are pioneering innovative techniques to deliver net zero carbon and other sustainability goals, helping project teams to acquire new skills and experience and share learnings, with mutual benefits for organisations along the real estate value chain. 5. Retrofit and redevelopment are driven by other factors besides net zero carbon and deliver a wider range of positive sustainability outcomes. The primary driver for commercial building retrofit or redevelopment is to unlock the potential of economically and/or environmentally stranded assets and maximise their value. Net zero carbon is generally approached within the context of a holistic asset sustainability strategy and is one of a wider range of positive outcomes delivered, such as additional lettable space with lower operational costs, increased occupier health and wellbeing, enhanced public realm, climate change resilience, biodiversity gain and air quality improvements. 6. The delivery of net zero carbon buildings presents common challenges including costs, skills shortages, information gaps and tenant engagement to maintain target energy performance. These challenges are common to both retrofit and redevelopment approaches, and specifically include a lack of internal capacity and external availability of specialist skills, additional costs associated with lower embodied carbon materials and net zero carbon infrastructure and the practical difficulties of obtaining reliable information about existing buildings and building products. 7. Net zero carbon is most effectively delivered via a strategy that is tailored to the individual asset, both its physical attributes and long-term commercial proposition. Retrofit, redevelopment and hybrid approaches can each be effective, and there is no ‘one size fits all’ solution. Net zero carbon buildings are also more likely to create and sustain additional value when developed according to holistic sustainability principles, with due consideration to climatic changes and evolving societal and market trends. This is the latest research paper to be released by the London Property Alliance, authored by JLL, and produced with support from BentallGreenOak, British Land, Derwent London, GPE and Landsec. To find out more visit: https://tinyurl.com/38ys3jk7 www.londonpropertyalliance.com