It is now almost universally accepted that we are not all going back to the office, at least not full time. So what does that mean for the proportion of commercial real estate that will be surplus to requirements? As the post-Covid world begins to take shape, property owners must find an alternative use for potentially many millions of square feet of once-prime space.  

Simply knocking it down and building something else is the typical solution for property that has become obsolete, though the waste of materials and the embodied carbon this represents is becoming much less acceptable. If only there was some wealthy, space-hungry group of building users, keenly aware of the need to manage their carbon footprint, just waiting to occupy all that empty property …

It’s not as far-fetched as it sounds. To say the data centre sector is growing is a colossal understatement. Some US$100bn has been poured into the asset class over the past decade, and the signs are that it has barely got started. The amount of data the world generates and uses is increasing at a vertiginous rate, with some 90% of all the data that has ever existed being created over the past two years.

The global datasphere, Seagate predicts, will grow from 45 zettabytes in 2019 to 175 zettabytes by 2025 — and even this might be a conservative estimate because the pandemic has had such a dramatic impact on internet traffic. Pre-Covid, it had been forecast to grow by an already substantial 28% in 2020. In the event, everything from Zoom conferencing to home schooling boosted world traffic by an astonishing 47%, with a commensurate spike in data usage.

You don’t need to know what a zettabyte is* to see that this is a growth market. But like every young and expanding sector, it has issues. For a start, data centers — essentially large warehouses that house little other than racks of processors — use mind-boggling amounts of power. Individual buildings routinely require 30-60MW, and the campuses of the giant “Hyperscalers” can use 250 or even 500MW of electricity, or the same as a small town. Already the world’s data centers together consume about the same amount of power, according to some estimates, as the whole of Spain. The carbon footprint of data is rapidly becoming a more high-profile issue. Data centers also take up vast amounts of land, one factor that has traditionally pushed them to less expensive out-of-town locations. The world’s largest campus, The Citadel, under construction in Nevada, covers an area of 7.2 million sq ft, or nearly 100 soccer pitches. It also includes, at 1.3 million sq ft, the world’s largest individual data center building.

To locate these extraordinary facilities in empty office blocks would seem to be synergistic — providing more than simply high-rent tenants for the owners. “Most of the embodied carbon from the construction of a data center is in the foundation, structure and envelope,” points out Ben Stanley, data center sustainability consultant at WSP in Colorado. “Reusing existing buildings would save most of that, with benefits for the carbon footprint of the operator.”

There is an even more compelling reason for city center conversions and it’s called “the edge”. This is the drive to decentralize data storage and bring it closer to users, to support growing applications like the Internet of Things. Tech analyst Gartner has predicted that as much as 75% of all data could be stored at the network edge, compared to 10% today. Edge data centers are smaller, often specialized for one client or sector, and located nearer to population centers. This is because speed rather than scale is of primary importance, explains Kevin Imboden, senior research manager for Cushman & Wakefield’s global data center advisory group, based in California’s Silicon Valley. “Edge-style data centers offer a particular advantage over out-of-town hyperscale facilities because there are many applications where latency — the time lag between asking for information and receiving it back — is vital.”

This is why high-performance data centers are located close to the centers of financial hubs such as London and Frankfurt, allowing automated trading systems to take advantage of tiny market fluctuations. But Imboden sees other potential applications: “If driverless cars ever become a thing, they too would need very low latency — and that means physical proximity.”

Conversion opportunities could also arise from recent changes in the character of the data center market. “Cloud services, which are generally located in large, out-of-town data centers, can be expensive,” says Imboden. “This is encouraging users to adopt a hybrid approach.” So, in addition to out-of-town space, they might also have some of their own private racks in a shared or “co-location” data center, or some actually in their office building. “If they require low latency, they might use a small, specialist, in-town data center facility. They can optimize that mix to suit their business. Smaller deployments will begin making further sense as the edge develops.” 

So how easy is it to convert an office building into a data center? Given that the demands from both a structural and servicing point of view are very different, it’s definitely not just a case of swapping out desks for server racks. 

Due to the need for a guaranteed UPS (uninterrupted power supply), data centers require massive battery capacity that can take over in a microsecond should the grid supply fail. This is typically installed on the ground floor. “Even though they only need to supply power for a few minutes — the time it could take before emergency generators are fired up — that’s still a lot of power and a lot of heavy batteries,” says Rich Donaldson, principal engineer with WSP firm, kW Mission Critical Engineering in Atlanta, Georgia. The generators are also substantial and heavy, he adds. “Even the racks create much more loading than you would need for an office. So, it’s structurally easier for them also to be ground floor. Data centers are usually single storey to lower the construction cost, although they can be multistorey when site acreage is constrained.”

The weight of equipment is not the only difference: there’s also floor-to-ceiling height. Floor heights in a data center are around 1.5 times those of office buildings, so it would require two office floors to provide one for a data center. “Data centers generally require 14ft with another 4 or 5ft clear above to take all of the cooling and extra services infrastructure they need,” says Donaldson. The existing power supply will need to be significantly increased, and the utility company might not be able to route more power or have space to install a substation. Finally, there’s the back-up infrastructure: storing and distributing fuel oil is more difficult in city center locations, for example. 

Despite the technical challenges, there are a growing number of successful conversions. “There’s one in an old print works in London which, given the connection with information distribution, seems quite symbolic,” Imboden says. This worked because there was already an industrial power supply to run the presses, there was a large floor-to-ceiling clearance, and the structure was strong because the print machinery was heavy. Similarly, he points to a recent shopping mall conversion, which had sufficient ceiling heights for extra data center services. As for converting office blocks, he says there is potential: “I see maybe a small facility next to a 5G phone antenna, or at the top of a building to connect the users below.”

In fact, converted data centers are already a well-established feature of the Hong Kong market. Being small and densely populated, Hong Kong has no cheap, out-of-town land. But then for the same reason it also has no latency problem – a boon to the city’s considerable financial services sector. Here data centers are located not in converted office blocks, but in converted warehouses.

“In Hong Kong, because of the space constraints, we have warehouses — or “godowns” — which are multistorey,” explains Eric Sin, an executive director at WSP and specialist in data center design. “As heavy industry here has declined, these buildings have become available, and we actually have government incentives to convert them to data centers.” Although they are multistorey, such conversions make sense as the godowns have heavy concrete structures and usually plenty of floor-to-ceiling height. In addition, they are cheaper than more central office blocks, and located away from residential areas, “so the noise and smell of back-up diesel generators is less of a problem”.

WSP is currently converting four floors of a former godown to provide a client with a 6MW data center. “Every conversion has its own challenges,” says Sin’s colleague Lydia Lun, an architect and project manager for the China region. “This project will need two additional 11kV feeders to be provided by the power company, meeting building louvre and flat roof area requirements for generator exhaust, and there’s limited vertically aligned space for risers. So very efficient planning is required.”

For the future, continuing improvements in the design of computer hardware should improve the feasibility of converting more constrained buildings: “The processor racks themselves are already less demanding than they use to be,” says Imboden. “For example, they used to be kept at 60°F because that was optimum for the processors. They can now operate at more like 75°F. Less cooling equals more efficiency. Ten years ago, data centers' power usage efficiency was something like 1.7 — the ‘point seven’ being the power used for cooling and other non-processing activity. Now, with warmer environments and more efficient, evaporative, cooling, it’s more like 1.2, or even less.” Further innovations, such as the liquid cooling of waterproof racks, are beginning to make an impact and could further reduce the need for bulky air-conditioning plant. 

As in other sectors, as operational carbon emissions come down, the embodied carbon of buildings will account for a greater proportion of the total, and this too will drive interest in reusing existing structures rather than meeting demand with new construction alone. 

Moving data center capacity into towns also opens up possibilities regarding the vast amounts of waste heat that these facilities generate, particularly in colder climates. For Amazon’s headquarters in downtown Seattle, completed in 2018, WSP’s building services design included piping waste heat from an adjacent data center into a district heating plant for the whole development, which helped it to exceed stringent local energy requirements. Similarly a 98,000sq ft, 4MW high-performance computer facility designed by kW MCE for a downtown location, uses waste heat recovery to provide warm water to a neighboring high-rise building. This could also be a solution for residential buildings: a planned scheme in Amsterdam will use warm water from a data center cooling system to heat local housing. 

The successful conversion of any building to data center use will come down to an insightful identification of opportunities, coupled with meticulous design. Fundamentally, this is an essential way of expanding the pool of developable land in mature markets, says WSP director Austin Wikner. His London building services team is already working on one feasibility study and he thinks there will be many more such projects. “There are challenges, but they can be overcome – and in doing so, we open up huge opportunities for data center companies to obtain space in locations that were not previously possible,” he says. “It’s similar to the way that major developers are now building over railways and electricity substations. Many of the easy sites are gone, so we need to work a bit harder to find the next set of opportunities.”

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Words by Tony Whitehead