Research
•Industrial buildings: build up or build out?
Where should we locate our industrial buildings? This article takes an initial look at the implications of building up on tight urban sites versus building out on unconstrained sites, using two recent HTS projects.
Introduction
Demand for industrial space is increasing, driven by AI data centres, investment in advanced manufacturing, and storage and logistics buildings for e-commerce. Industrial buildings are vast and need to support loads as much as ten times greater than typical office or educational buildings, leading to big carbon footprints. Clients and developers are, rightly, seeking well-designed low-carbon industrial buildings. How should we meet this brief? Should we build up on tight urban sites, or spread out over unconstrained ones? And what about impacts beyond embodied carbon, such as land use, biodiversity and transportation?
Project description
To explore this question, we compare two recent, anonymised industrial buildings designed by HTS: Building Out, a single-storey industrial building on the outskirts of a city, and Building Up, a four-storey industrial building in a dense urban centre. Both buildings are supported by steel beams and columns, and designed for the substantial imposed loads required in industrial use.1
1 The loads a building is designed to support depends on its use. Industrial buildings may need to accommodate significant storage loads and vehicle movements within the building. Both Building Out and Building Up have a 50 kN/m2 allowance at ground floor, and Building Up has 25 kN/m2 at level 1 and 15 kN/m2 above. By comparison, an office is typically designed for 2.5 kN/m2.
Building Out
Building Up
Structural upfront embodied carbon
Starting with the most readily quantified measure: the structural upfront embodied carbon. For industrial buildings, the IStructE’s How to Calculate Embodied Carbon recommends expressing carbon intensity per unit of internal volume delivered, as well as internal area. This better reflects the value delivered by large-volume spaces.
Table 1 - Carbon intensity of structure. Structural carbon is substructure and superstructure together. GIA = gross internal area, and GIV = gross internal volume.
On this basis, the structural carbon intensity of Building Up is almost six times that of Building Out. The multi-storey arrangement, heavy imposed loads on upper floors and wide 10-metre grid spacing require a stronger structural frame with deep beams to safely transfer loads from the upper stories into the ground. By contrast, Building Out has a relatively lightweight repeating steel frame that supports only the roof.
Both buildings were designed and built to a standard specification and did not include measures to reduce embodied carbon beyond market averages. Incorporating more impactful carbon saving methods such as reused steel, structural timber or multicomponent cements may improve the relative case for Building Up.
What about the external works?
The picture changes slightly when external works are included. Building Out is located on the outskirts of a city, on a site around eight times the size of Building Up. Serving that site requires sizeable attenuation tanks and a large loading yard, both of which add upfront embodied carbon.2
Table 2 – Structural and external carbon intensity of the projects, per m² gross internal area and m³ gross internal volume
While the external works reduce the gap between the two projects, Building Out still provides 4.5 times more gross internal volume for each kilo of embodied carbon than Building Up. A significant difference, one driven mainly by the site’s geographic location. This illustrates a key principle of PAS 2080 and other guidance: the greatest opportunities to influence carbon occur during the earliest strategic stages of a project.
2 External works are rarely reported in detail in embodied carbon assessments, despite their significance at site scale. On these two projects, the main contributors were the attenuation tank and yard concrete at Building Out. Improving reporting in this area would help the industry better understand carbon impacts beyond the building itself.
Alignment with industry targets
The only body currently providing net-zero criteria for industrial buildings is the Pilot Version of the UK Net Zero Carbon Building Standard (UK NZCBS). To test alignment with net zero limits, we assume the structural embodied carbon makes up 75% of the building’s total embodied carbon. This is a rough estimate based on project experience, so the result should be treated as indicative only.
On that basis, Building Up exceeds the NZCBS limits, but only by about 25%. Building Out is comfortably within the limits, suggesting it could meet a net-zero-aligned upfront carbon target at practical completion. Full UK NZCBS alignment depends on many other elements throughout building’s whole life, which are beyond the scope of this article.
Looking beyond embodied carbon
Embodied carbon is not the only environmental metric that matters. The fact we can measure and report it has led to the risk of applying a blinkered approach. Building Out is on a much larger site and its structural efficiency depends on this spatial freedom. This raises a broader question: how much land is used to deliver each square metre of industrial space?
A simple way to describe this is through land intensity, calculated here as a site area divided by gross internal area. A lower figure indicates more intensive use of land.
- Building Out: 2.44 m2 site area per m2 GIA
- Building Up: 0.54 m2 site area per m2 GIA
By this measure, Building Out uses about 4.5 times as much land per square metre of GIA than Building Up. In other words, the lower upfront carbon solution is also the more land intensive.
Other whole life cycle impacts of land intensity, such as transport, can be captured in a whole life cycle assessment of embodied and operations carbon emissions for the site (beyond our scope).
But the impact of land use change is not neatly captured in current reporting mechanisms, and we risk missing wider environmental effects. Land use change is a major driver of biodiversity loss. Land intensity is only a proxy: biodiversity outcomes depend heavily on whether a site is previously developed land, existing habitat, or land with potential for restoration.
Conclusion
These two case studies raise important questions about how and where we should build industrial space in future. In this comparison, building low and out is markedly lower in upfront embodied carbon than building up on a constrained urban site for heavily loaded industrial use. It is also much more likely to align with current net-zero carbon benchmarks.
But that is not the whole story. The lower-carbon solution is also the more land-intensive one, and that brings wider questions about land use, biodiversity and transport. A narrow focus on upfront embodied carbon alone could therefore push decision making towards out-of-town development without fully accounting for its broader environmental consequences.
The market for industrial buildings is predicted to continue growing, with a strong occupier preference forecast for sustainable and modern spaces. Industrial buildings are essential to the modern economy, and there will rarely be a single right answer. But the choice between building up and building out should be made with a full view of the trade-offs.
