Counting Carbon in Airspace Development

Introduction

In an era where urban space is at a premium, the concept of building upwards rather than outwards presents a transformative solution for cities like London. Airspace development offer a strategic method to utilize existing structures to meet UK housing demands without further straining land resources. This not only aligns with sustainable urban development goals but also addresses the critical need for space in densely populated areas.

The Promise of Vertical Extensions

Recent work by engineering and design firm Arup highlights the potential of adding floors to buildings, particularly low- to medium-rise structures originally constructed in the 1960s. These Airspace Developments are now increasingly seen as viable options to create new homes in desirable locations. The government has recognized this potential, introducing new permitted development rights in England that allow residential extensions of up to two storeys without full planning permission, simplifying the development process and encouraging more projects. Next Level Airspace have written about this here.

Airspace development contribute significantly to sustainable development by reducing material consumption and leveraging existing building stock, thereby minimizing carbon emissions. These projects align with several UN Sustainable Development Goals, such as responsible consumption, affordable and clean energy, and sustainable cities and communities.

Technical Challenges and Solutions

Despite their benefits, Airspace developments present unique structural challenges that require careful consideration and innovative engineering solutions. One major challenge is ensuring that the existing buildings can support the additional weight and stresses of the new storeys. This often necessitates a detailed structural appraisal of the existing building to assess its capacity and condition, which may involve intrusive investigations that can be disruptive.

Wind loading also becomes a significant factor as the building’s height increases. Modern codes for wind loads must be considered, which may have changed since the original construction. The stability of the building, particularly if it lacks a designed stability system in one direction, must be addressed to ensure safety against overturning.

Next Level Airspace team have a collective 40 years experience designing and constructing buildings and understand the delicate considerations required for a structural assessment of an airspace development.

Carbon Impact and Environmental Considerations

One of the critical aspects of vertical extensions is their carbon impact. By utilizing lightweight materials such as light-gauge steelwork , the demand on the existing structure can be minimized, and the construction process can be more environmentally friendly. These materials can be prefabricated, which reduces on-site construction time and disruption, further contributing to a project’s sustainability.

The case study discussed by Arup illustrates the varying scenarios for extending upwards, ranging from adding two storeys with minimal modifications to more complex designs that require an independent support structure around the existing building. Each scenario has different implications for embodied carbon, with more extensive modifications generally leading to higher carbon costs. However, even the more carbon-intensive options are preferable to demolishing and rebuilding, which would have a far greater environmental impact.

Embodied carbon investigations for Airspace development [1}

Conclusion

As cities continue to grow, the pressure on urban planners and engineers to find sustainable solutions to housing shortages increases. Vertical extensions offer a promising avenue not only to meet housing needs but also to contribute to the broader sustainability goals of urban development. By embracing innovative architectural designs and engineering solutions, we can transform existing buildings into modern, energy-efficient homes that cater to the needs of the urban population without compromising on environmental values or the aesthetic and historical character of our cities.

This article was inspired by the paper presented in The Structural Engineer, Volume 99, published 4 May 2021 https://www.istructe.org/journal/volumes/volume-99-(2021)/issue-5/vertical-extensions-technical-challenges-carbon/

References

[1] Vertical extensions: technical challenges and carbon impact, The Structural Engineer, Volume 99, published 4 May 2021